DESIGN AND FABRICATION OF SOLAR LIGHT RESPONSIVE NEW METAL ORGANIC FRAMEWORKS

FOR PHOTOCATALYSIS

NUR ATIQAH BINTI SURIB

DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING

UNIVERSITY OF MALAYA KUALA LUMPUR

2018

DESIGN AND FABRICATION OF SOLAR LIGHT

RESPONSIVE NEW METAL ORGANIC

FRAMEWORKS FOR PHOTOCATALYSIS

NUR ATIQAH BINTI SURIB

DISSERTATION SUBMITTED IN FULFILMENT OF

THE REQUIREMENTS FOR THE DEGREE OF MASTER

OF ENGINEERING SCIENCE

DEPARTMENT OF CIVIL ENGINEERING

FACULTY OF ENGINEERING

UNIVERSITY OF MALAYA

KUALA LUMPUR

2018

ii

UNIVERSITY OF MALAYA

ORIGINAL LITERARY WORK DECLARATION

Name of Candidate: Nur Atiqah Binti Surib

Matric No: KGA 140014

Name of Degree: Master of Engineering Science

Title of Project Paper/Research Report/Dissertation/Thesis (“this Work”):

Design and Fabrication of Solar Light Responsive New Metal Organic Frameworks for

Photocatalysis.

Field of Study: Environmental Engineering

I do solemnly and sincerely declare that:

(1) I am the sole author/writer of this Work;

(2) This Work is original;

(3) Any use of any work in which copyright exists was done by way of fair

dealing and for permitted purposes and any excerpt or extract from, or

reference to or reproduction of any copyright work has been disclosed

expressly and sufficiently and the title of the Work and its authorship have

been acknowledged in this Work;

(4) I do not have any actual knowledge nor do I ought reasonably to know that

the making of this work constitutes an infringement of any copyright work;

(5) I hereby assign all and every rights in the copyright to this Work to the

University of Malaya (“UM”), who henceforth shall be owner of the

copyright in this Work and that any reproduction or use in any form or by any

means whatsoever is prohibited without the written consent of UM having

been first had and obtained;

(6) I am fully aware that if in the course of making this Work I have infringed

any copyright whether intentionally or otherwise, I may be subject to legal

action or any other action as may be determined by UM.

Candidate’s Signature Date:

Subscribed and solemnly declared before,

Witness’s Signature Date:

Name:

Designation:

iii

DESIGN AND FABRICATION OF SOLAR LIGHT RESPONSIVE NEW

METAL ORGANIC FRAMEWORKS FOR PHOTOCATALYSIS

ABSTRACT

Design and synthesis of multi-dimensional metal organic frameworks has attracted

much attention not only due to their intriguing structures and unique properties, but also

for their potential applications especially in catalysis. Recently, much effort has been

devoted to develop new photocatalyst based on MOFs, motivated largely by a demand

for solving pollution problems in view of their potential applications in the green

degradation of organic pollutants. MOFs, known as coordination polymers are

crystalline materials constructed from metal ions or clusters bridged by organic ligands

to form one-, two-, or three-dimensional infinite networks. There are several methods

have been applied for synthesis of MOFs particularly solvothermal, hydrothermal,

microwave-assisted, electrochemical, mechanochemical and sonochemical synthesis. In

this work, new Cadmium and Copper based Metal Organic Framework (MOF) was

synthesized under hydrothermal and solvothermal conditions. Its structure was resolved

by single crystal X-ray diffraction and further characterized by Powder X-ray

diffraction (PXRD), Field Emission Scanning Electron Microscopy (FESEM), Infrared

Spectra (IR), Thermogravimetric (TGA), UV-Vis, Photoluminescence (PL) and X-ray

photoelectron spectroscopy (XPS) analysis. The Cd-MOF and Cu-MOF were

photocatalytically active for degradation of 2-chlorophenol (2-CP) under solar light

irradiation where 69% and 100% of phenol removal was observed respectively. To

improve photocatalytic activity of Cd-MOF, different metal ions such as Ag+, Fe

3+ and

Zn2+

were introduced into the framework through ion-exchange reaction. The UV-Vis

results revealed that Fe-Cd-MOF showed an enhanced photoresponse in the visible

region, whereas the photoresponse of Ag-Cd-MOF and Zn-Cd-MOF in the ultraviolet

light region. Photocatalytic performances of synthesized materials were investigated for

iv

degradation of 2-CP. Among them, Cd-MOF intercalated with Fe3+

exhibited excellent

photocatalytic activity compared with Cd-MOF, degrading 92% of 2-CP in 5 hours. It

can be attributed to the intercalation of Fe3+

, which reduced energy gap of pure MOF,

thus increases photocatalytic efficiency.

Keywords: MOF, photocatalyst, solvothermal, hydrothermal, degradation.

v

REKA BENTUK DAN FABRIKASI CAHAYA SOLAR RESPONSIF LOGAM

RANGKA KERJA ORGANIK YANG BARU UNTUK FOTOPEMANGKINAN

ABSTRAK

Reka bentuk dan sintesis “Metral Organic Frameworks (MOFs)” telah menarik banyak

perhatian bukan sahaja kerana struktur menarik dan ciri-ciri yang unik, tetapi juga potensi

aplikasi terutama sebagai pemangkin. Pada masa kini, banyak usaha telah ditumpukan untuk

membangunkan fotokatalis baru berdasarkan MOFs, bermotivasi sebahagian besarnya oleh

permintaan untuk menyelesaikan masalah pencemaran memandangkan potensi applikasi

degradasi hijau bahan pencemar organik. MOFs, dihasilkan daripada ion logam atau ligan

organik untuk membentuk satu, dua, atau tiga rangkaian dimensi. Terdapat beberapa kaedah

telah digunakan untuk sintesis MOFs antaranya ialah solvotherma, hydrotherma, ketuhar

gelombang mikro, elektrokimia, mechanokimia and sonokimia. Dalam kajian ini, MOF

berdasarkan Cadmium dan Copper telah disintesis masing-masing melalui cara hidroterma dan

solvotherma . Strukturnya telah diselesaikan dengan kristalografi sinar-X turut dicirikan melalui

serbuk pembelauan Sinar-X (PXRD), Mikroskopi Pengimbasan Elektron Perlepasan Medan

(FESEM), Infra-merah Spektra (IR) Analisa Gravimetri Terma (TGA), UV-Vis, fotoluminesen

(PL) dan Spektroskopi Fotoelektron Sinar-X (XPS) analisa. Cd-MOF dan Cu-MOF adalah

fotokatalis yang aktif untuk degradasi 2-klorofenol (2-CP) di bawah sinaran cahaya matahari di

mana 69% dan 100% daripada penyingkiran fenol diperhatikan. Untuk meningkatkan aktiviti

foto pemangkin MOF tulen, ion logam yang berbeza seperti Ag+, Fe

3+ dan Zn

2 telah

diperkenalkan ke dalam rangka kerja melalui tindak balas pertukaran ion. Keputusan UV-Vis

mendedahkan bahawa Fe-MOF menunjukkan tindak balas cahaya di kawasan cahaya tampak,

sedangkan Ag-MOF dan Zn-MOF hanya di kawasan cahaya ultraviolet. Kebolehan fotokatalitik

bahan MOF didopkan dengan ion logam telah disiasat melalui proses degradasi 2-CP.

Diantaranya, Cd-MOF didopkan dengan Fe3+

mempamerkan aktiviti fotocatalitik yang

cemerlang berbanding dengan Cd-MOF tulen, yang mana 92% degradasi 2-CP telah dicapai

vi

dalam masa 5 jam. Ia boleh dikaitkan dengan kehadiran ion Fe3+

, yang mana mengurangkan

jurang tenaga di dalam Cd-MOF tulen, seterusnya meningkatkan kecekapan fotokatalitik.

Keywords: MOF, fotokatalis, solvotherma, hydrotherma, degradasi.

vii

ACKNOWLEDGEMENTS

All praises be to the mighty Allah, the Merciful and the Beneficent for the strength and

blessing in the completion of this study.

First of all, I want to express my sincere appreciation and gratitude to my

supervisor Dr. Saravanan Pichiah and Prof. Dr. Shaliza Ibrahim for their valuable

comments, encouragement, constant support and guidance during the period of this

study in order for me to complete my thesis.

A big thank you also goes to my friends and lab mates especially Dr. Leong, Dr.

Sim, Dr. Kang, Dr. Azimatul, Ranjini, Sharmini, Ilya and Shan for their willingness and

helping me when I had problems with experiments and also for data analysis. Further

thanks are extended to laboratory assistant especially En. Faiz, Mdm Rozita and Mdm

Alya who guided me use all types of equipment and machine in the laboratory.

Many thanks to Ministry of Higher Education, Malaysia for the financial

support received under MyBrain15 program and University of Malaya for

Postgraduate Research Grant (PG 229-2015A).

At last, I would like to extend my sincere thanks to my family especially my

mother Pn Khadijah and my late father En Surib Bin Jumaat who have supported and

helped me throughout my master journey. Without their endless encouragement, support

and love it would not be possible for me to finish this thesis.

viii

TABLE OF CONTENTS

Original Literary Work Declaratiom…………………………………………………….ii

Abstract…………………………………………………………………………………iii

Abstrak…………………………………………………………………………………...v

Acknowledgements ..................................................................................................... vii

Table of Contents ....................................................................................................... viii

List of Figures............................................................................................................... x

List of Tables ............................................................................................................. xiii

list of Symbols and Abbreviations .............................................................................. xiv

List of Appendices .................................................................................................... xvii

CHAPTER 1: INTRODUCTION .................................................................................. 1

1.1 Background ......................................................................................................... 1

1.2 Problem Statements ............................................................................................. 4

1.3 Objectives of Study .............................................................................................. 5

1.4 Report Outline ..................................................................................................... 5

CHAPTER 2: LITERATURE REVIEW ...................................................................... 7

2.1 Metal Organic Frameworks (MOFs) – Photocatalysis .......................................... 7

2.2 Design and Synthesis of MOFs ............................................................................ 9

2.2.1 Metal Center ......................................................................................... 11

2.2.2 Organic Linkers .................................................................................... 13

2.3 Synthesis Methods ............................................................................................. 15

2.3.1 Hydrothermal and Solvothermal Synthesis ............................................ 18

2.3.2 Microwave Synthesis ............................................................................ 19

2.3.3 Electrochemical Synthesis ..................................................................... 19

ix

2.3.4 Sonochemical Synthesis ........................................................................ 19

2.3.5 Mechanochemical Synthesis ................................................................. 20

2.4 Other Application .............................................................................................. 21

2.4.1 Gas Storage ........................................................................................... 21

2.4.2 Sensing ................................................................................................. 23

2.4.3 Catalysis ............................................................................................... 25

CHAPTER 3: METHODOLOGY ............................................................................... 27

3.1 Materials ............................................................................................................ 27

3.2 Synthesis of Cd-MOF ........................................................................................ 27

3.2.1 Intercalation of Metal Ions into Cd-MOF .............................................. 29

3.3 Synthesis of Cu-MOF ........................................................................................ 30

3.4 Characterization ................................................................................................. 31

3.4.1 Single Crystal Structure Determination ................................................. 32

3.5 Solar Photocatalysis Experiment ........................................................................ 32

CHAPTER 4: RESULTS AND DISCUSSION .......................................................... 35

4.1 Inherent Physical-Chemistry of Cd-MOF and Metal Ions Intercalated Cd-MOF. 35

4.2 Cu-MOF: Inherent Physical-Chemistry .............................................................. 70

CHAPTER 5: CONCLUSION AND SUGGESTIONS ............................................. 84

5.1 Conclusion ......................................................................................................... 84

REFERENCES………………………………………………………………………..86

APPENDIX .................................................................................................................. 101

x

LIST OF FIGURES

Figure 2.1: Mechanism proposed for MO photodegradation on UTSA-38 activated

under UV and visible light ............................................................................................ 9

Figure 2.2: Graphic illustration of MOF structure with different dimensionalities ...... 10

Figure 2.3: Different types of linkers used in MOFs. .................................................. 14

Figure 2.4: Six different coordination modes of carboxylate ligands. .......................... 15

Figure 2.5: Illustration of emission possibilities in a porous MOF .............................. 24

Figure 3.1: Flowchart proposed approach in synthesis of new metal organic

frameworks. ................................................................................................................ 28

Figure 3.2: Photograph synthesized Cd-MOF and schematics of reaction involved in the

synthesis. .................................................................................................................... 29

Figure 3.3: Snap shots of (a) Ag-Cd-MOF, (b) Fe-Cd-MOF and (c) Zn-Cd-MOF (d)

Cu-MOF. .................................................................................................................... 30

Figure 3.4: Graphical illustration of adopted solar photocatalysis experiment. ............ 34

Figure 3.5: Calibration curve for 2-chlorophenol. ....................................................... 34

Figure 4.1: (a) The coordination environment of Cd (II) ion in Cd-MOF matrix and its

(b-c) 3D network......................................................................................................... 38

Figure 4.2: (a) Powder XRD pattern of cadmium based MOF, (b) Simulated based on

crystal information’s obtained from single crystal diffraction and (c-e) powder XRD of

metal ions intercalated Cd-MOF. ................................................................................ 41

Figure 4.3: Powder XRD pattern of pure Cd-MOF and metal ions intercalated Cd-MOF

in (0 0 3) direction. ..................................................................................................... 42

Figure 4.4: Morphology of (a) Cd-MOF, (b) Ag-Cd-MOF, (c) Fe-Cd-MOF and (d) Zn-

Cd-MOF obtained under different magnification. ........................................................ 44

Figure 4.5: FTIR spectrum of (a) pure Cd-MOF, (b) Ag-Cd-MOF, (c) Fe-Cd-MOF and

Zn-Cd-MOF. ............................................................................................................... 47

Figure 4.6: Thermogravimetric curve of (a) Cd-MOF, (b) Ag-Cd-MOF, (c) Fe-Cd-

MOF and (d) Zn-Cd-MOF. ......................................................................................... 49

Figure 4.7: (a) Optical property (b) energy gap of the synthesized MOFs. .................. 51

xi

Figure 4.8: Photoluminescence spectra of free H4btec linker, Cd-MOF, and intercalated

Cd-MOF at room temperature (λex= 325nm). .............................................................. 54

Figure 4.9: XPS spectrum of (a) Cd-MOF and Close up survey at (b) Cd, (c) C and (d)

O core level. ............................................................................................................... 57

Figure 4.10: XPS spectrum of (a) Ag-Cd-MOF, (b) Fe-Cd-MOF and (d) Zn-Cd-MOF

(inset: close up for Cd core level in Ag-CdMOF, Fe-CdMOF and Zn-CdMOF

respectively). .............................................................................................................. 59

Figure 4.11: XPS spectrum of intercalated metal ions Cd-MOF (a) Ag+ (b) Fe

3+ and (c)

Zn2+

. ........................................................................................................................... 60

Figure 4.12: (a) Effect of catalyst loading, (b) effect of pH on degradation of 2-CP for

Cd-MOF and (c) Solar light photocatalysis pure and metal ions intercalated Cd-MOF on

degrading aqueous solution 2-CP. ............................................................................... 64

Figure 4.13: Reusability study of (a) Cd-MOF and (b) Fe-Cd-MOF in degrading

aqueous 2-CP. ............................................................................................................. 65

Figure 4.14: Structural comparison of the virgin and used (a) Cd-MOF and (b) Fe-Cd-

MOF. .......................................................................................................................... 66

Figure 4.15: The fitted reaction kinetics of 2-CP degradation triggered by solar light. 67

Figure 4.16: Mechanistic of synthesized MOF on excitation under solar light on

degradation of 2-CP (a) pure Cd-MOF and (b) Fe- Cd-MOF ....................................... 69

Figure 4.17: Structure of synthesized Cu (II) MOF structure. ..................................... 70

Figure 4.18: As synthesized XRD pattern of copper (II) MOF with JCPDS reference

peak. ........................................................................................................................... 71

Figure 4.19: Morphology of Cu (II) MOF. ................................................................. 72

Figure 4.20: FTIR of Cu- MOF scuffled with H4btec and Bimb linker. ...................... 74

Figure 4.21: Thermogravimetric profile of Cu-MOF scuffled with dual linkers. ......... 74

Figure 4.22: (a) Optical characteristics of free linkers and Cu-MOF, (b) energy gap of

synthesized Cu-MOF. ................................................................................................. 76

Figure 4.23: Photoluminescence spectrum of linkers and Cu-MOF. ........................... 77

Figure 4.24: (a) Full XPS spectrum of Cu-MOF, (b) close up survey at Cu core level. 78

Figure 4.25: (a) Photocatalysis efficiency of Cu-MOF on 2-CP in presence of solar light

(b) Reaction kinetic of degradation pattern exhibited by the Cu-MOF. ........................ 80

xii

Figure 4.26: (a) Reusability of Cu-MOF (b) Structural stability of Cu-MOF before and

after use. ..................................................................................................................... 81

Figure 4.27: Schematic illustration of formation of ROS in the Cu-MOF for active

degradation of 2-CP. ................................................................................................... 83

xiii

LIST OF TABLES

Table 2.1: Coordination environment of components in MOFs ................................... 12

Table 2.2: Summary of various methods in synthesis of MOFs ................................... 16

Table 2.3: DOE targets for on-board hydrogen storage system. .................................. 23

Table 4.1: Single crystal profile extracted for Cd-MOF. ............................................. 36

Table 4.2: Selected bond and angles in Cd-MOF extracted from Single crystal XRD. 39

Table 4.3: Percentage degradation of 2-CP with synthesized MOFs under solar light

irradiation. .................................................................................................................. 62

xiv

LIST OF SYMBOLS AND ABBREVIATIONS

Symbol/Abbreviation Meaning

m2g

-1 : Square Meter per Gram

cm3g

-1 : Cubic Centimeter per Gram

wt : Weight

cm2cm

-3 : Square Meter per Cubic Centimeter

cm3cm

-3 : Cubic Centimeter per Cubic Centimeter

v/v : Volume per Volume

°C : Degree Celsius

% : Percentage

h : Hours

W : Watt

kg/kg : Kilogram

g : Gram

s : Seconds

min : Minutes

mm : Milimetre

mA : Milliampere

kHz : Kilohertz

Hz : Hertz

MHz : Megahertz

% : Percentage

M : Molarity

mL : Milliliter

Mmol : Milimol

K : Kelvin

*OH : Hydroxyl Radicals

*O2- : Oxygen Radicals

O2 : Oxygen

h+

: Proton (Holes)

e- : Electron

eV : Electronvolt

xv

Atm : Atmosphere standard

C : Carbon

H : Hydrogen

O : Oxygen

CO2 : Carbon Dioxide

H2 : Hydrogen

H2O : Water

1D : One-Dimensional

2D : Two-Dimensional

3D : Three-Dimensional

nm : Nanometer

d : Subshell d

Ru : Ruthenium

Mn : Manganese

Co : Cobalt

NO3- : Nitrate

NaNO3 : Sodium Nitrate

Max : Maximum

Min : Minimum

Zn : Zinc

Al : Aluminium

Ce : Cerium

ZnO : Zinc Oxide

DI : Deionized

SiO4 : Silicate

AlO4 : Aluminate

Cd(NO3)2.4H2O : Cadmium (II) Nitrate Tetrahydrate

H4btec : 1,2,4,5-Benzenetetracarboxylic Acid

DMF : N,N-Dimethylformamide

Bimb : Indole-3-Carboxaldehyde Azine

2-CP : 2-Chlorophenol

AgNO3 : Silver Nitrate

NaOH : Sodium Hydroxide

Fe(NO3)3.9H2O : Iron (III) Nitrate Nonahydrate

Zn(NO3)2.6H2O : Zinc (II) Nitrate Hexahydrate

xvi

Cu(NO3)2.4H2O : Copper (II) Nitrate Tetrahydrate

H2SO4 : Sulphuric Acid

MOCNs : Metal-Organic Coordination Networks

BPDC : 2,2’-Bipyridine-5,5’-Dicarboxylate

Trimesic acid : 1,3,4-Benzenetricarboxylate

NDC : Naphthalenedicarboxylic Acid

DMF : N,N’-Dimethylformamide

pytpy : 4-(4-Pyridyl)- 4,2:6,4-Terpyridine

BTB : Benzenetribenzoate

H3L :

N,N′,N″-Tris(4-Carboxyphenyl)-1,3,5-

Benzenetricarboxamide

dptz : 3,6-Di-(Pyridin-4-Yl)-1,2,4,5-Tetrazine

dpmtz :

3,6-Di-(Pyridin-4-Yl)-1,2-Dihydro-1-Mercapto-1,2,4,5-

Tetrazine

H3IDC : Imidazole-4,5-Dicarboxylic Acid

H2BDC : 1,4-Benzenedicarboxylic Acid

H2oda : Oxydiacetic Acid

H3BTC : Benzene-1,3,5-Tricarboxylic acid

BTB : 4,4’,4”-benzene-1,3,5-triyltribenzoate

INA : Isonicotinate

Dabco : 1,4-diazabicyclo[2.2.2]octane

Hta : Terephthalic Acid

NMP : 1-Methyl-2-Pyrrolidinone

(bpdc) : Biphenyldicarboxylate

(tcpb) : Tetrakis(4-Carboxyphenyl)benzene

CUMs : Coordinatively unsaturated metal sites

FOS : Functional Organic Sites

MNPs : Metal Nanoparticles (MNPs)

xvii

LIST OF APPENDICES

Appendix 1: Peak area value for photodegradation of 2-CP from UPLC

performance.……………………………………………………………..................101

1

CHAPTER 1: INTRODUCTION

1.1 Background

Water is essential for every living being on earth. There are approximately 1.2 billion

people lacking access to safe water and 3 billion have scarce sanitation for daily

activities (Shannon et al., 2008). The presence of various classifications of chemical

compounds in wastewater is being concerned for the living beings. One among these is

Endocrine Disrupting Chemicals (EDCs) chemicals with the potential to elicit negative

effects on the endocrine systems of beings. Chlorinated compounds such as 2-

chlorophenols (2-CP), 4-chlorophenols, 2,4-dichlorophenol (2,4-DCP) and

pentachlorophenol (PCP) are one such group categorized under EDCs. The United State

Environmental Protection Agency (USEPA) has listed phenols and its derivatives as one

of the top priority environmental disruptors (Rao et al., 2003). The fact being a C-Cl

bond in halo-hydrocarbons responsible for their lethal, carcinogenic characteristics and

non-biodegradable nature (Titus et al., 2004). CPs are introduced into the environment

as a result of several anthropogenic activities. Because of the presence of chloride ions

(Cl-) they possess antimicrobial properties and have been widely used as preservative

agents for wood, paints, vegetable fibers and leather and as disinfectants. In addition,

they are employed in many industrial processes such as synthesis intermediates or as

raw materials in the manufacturing of herbicides, fungicides, pesticides, insecticides,

pharmaceuticals and dyes (Sharma & Lee, 2016). CPs also generated as by-products

during waste incineration, the bleaching of pulp with chlorine, and in the dechlorination

of drinking water (Titus et al., 2004). Therefore, effective techniques need to be

developed to remove or minimize the concentration of CPs before releasing into the

ecosystem.

2

For years chlorophenols in water are removed through most common techniques like

adsorption, precipitation and coagulation. However, these traditional methods have

potential limitations because they do not completely eliminate or destroy these organic

pollutants and incapable of handling them while present in very low concentrations

(Astereki et al., 2016). Hence, it is essential to develop advanced, green and efficient

treatment technologies to limit and reduce their presence in aquatics. Heterogenous

photocatalysis a sub-classification of Advanced Oxidation Processes (AOPs) has

emerged as an viable candidate for effectively eliminating those CPs from aquatic

environments (Sin et al., 2011). They hold some benefits as they can operate with low

costs at ambient operating temperatures and pressures under light sources. More

importantly, this method can decompose a wide range of organic pollutants to CO2 and

H2O with very low concentration of addition by-products like HCl and even eventually

mineralize them without leaving secondary pollution (Chong et al., 2010). As of now,

semiconductor catalyst such as ZnO, CdS, ZnS, Fe2O3 especially TiO2 were widely used

as photocatalysts due to its relatively high efficiency and low cost (Chong et al., 2010;

Herrmann et al., 2007). However, there are several problems that limit their application

into water industry. Firstly, TiO2 has low photocurrent quantum yield due to electron–

hole recombination and low solar energy utilization efficiency resulting from the narrow

band gap (Eg = 3.2 eV) (Dong et al., 2015; Zaleska, 2008). Their fine particle size of

the TiO2, together with its large surface area-to-volume ratio and high surface energy

leads to a strong tendency for catalyst agglomeration. Lastly, post-separation of the

TiO2 catalyst is difficult after water treatment, which impedes the practicality in

industrial processes (Cui et al., 2013; Gao et al., 2011). Therefore, researchers are trying

to look for new photocatalysts with qualitative performances.

The Metal Organic Framework (MOF) have attracted the researcher with intense

interest due to their structural diversity, intriguing topologies and their significant

3

adoptability in numerous areas including catalysis, gas separation (Eddaoudi et al.,

2002; Foy et al., 2006; Sumida et al., 2011) and sensing (Guo et al., 2010; Luo &

Batten, 2010). MOFs composed of metal-containing nodes connected by organic

linkers through strong chemical bonds to form extended networks (Du et al., 2013; Lin

et al., 2014; Zhu & Xu, 2014). This favorable structural formation of MOFs make them

to act as semiconductors photocatalyst (Silva et al., 2010). For example MOFs

constructed by transitional metals like Zn (II), Cu (II), Cd (II) and Co (II) were

examined as photocatalyst using wide range of light spectrum i.e., UV to Visible (Guo

et al., 2012b; Wen et al., 2012; Wu et al., 2013; Xamena et al., 2007). Xamena was the

first to demonstrate as MOF as photocatalyst that actively functioned between 500-840

nm. He synthesized MOF-5 that composed of Zn4O and 1,4-Benzenedicarboxylic acid

make it more efficient in removing phenol (P) and 2,6-di-tert-butylphenol (DTBP) as

compared to and well-studied conventional TiO2, Aeroxide

P25 (Xamena et al., 2007).

Following him Wu and co-workers also studied another series of MOFs,

[Cu(hfipbb)(2,2′-bipy)(H2O)2]n and [Cu2(hfipbb)2(4,4′-bipy)(H2O)]n which showed good

photocatalytic properties for the degradation of rhodamine B (RhB) under visible light

irradiation (Wu et al., 2013). Though the researchers identified the inherent nature of

these MOFs not many works have been reported in this specific area. Motivated by this,

we are keen in preparing newer combinations of MOFs through facile and simple

hydrothermal route with potential doping of metal ions by ion exchange reactions for

improved solar light driven photocatalysis. The prepared MOF are deeply dissected with

various advanced microscopical and spectroscopical techniques. The photocatalytic

activities of developed materials were examined by performing solar photocatalysis

experiments with 2-cholorophenol as model pollutant.

4

1.2 Problem Statements

In modern times, the possibility of using MOFs in photocatalysis where photon

absorption produces a state of charge separation has been explored (He et al., 2014). In

comparison with traditional photocatalysts, MOFs are endowed with more satisfactory

photocatalytic efficiency and stability, making them prosperous candidate

photocatalysts for the decomposition of organics (Mahata et al., 2006; Silva et al.,

2010). Even though MOFs possess high stability, their poor photoresponse in the longer

wavelength band hinders applicability as alternative photocatalyst (Das et al., 2011; He

et al., 2014; Wang et al., 2009). This is primarily due to the wide energy gap and fast

recombination rate between photogenerated electrons and holes during the

photocatalytic process. Hence, the modification of MOF-based photocatalysts appears

to be significant (Dai et al., 2015; Li et al., 2015; Wang et al., 2015; Xu et al., 2014a). In

general, there are only two methods to obtain visible-light responsive MOFs. One them

is to select ligands or metal centers with visible-light response and the other is post-

synthetic functionalization (He et al., 2014). While doping metal ions into the

framework of MOFs is promising strategy. This is because suitable metal ion dopants

can tune energy gap of the photocatalyst and accelerate the separation of photo-induced

electrons and holes. The doped catalyst possesses a smaller energy gap and exhibits

improved photocatalytic functionality especially in the visible light region (He et al.,

2014; Li et al., 2015; Wang & Cohen, 2009; Xu et al., 2014a).

5

1.3 Objectives of Study

The major objective of the present dissertation is to develop new MOF for solar light

driven photocatalyst for water treatment application. To achieve the said objective

following strategy was adopted:

Design of MOF: To identify appropriate metal ion for the chosen linkers

with the ability to harvest solar light through a facile and simple route.

Modification of MOF: To tune the energy gap of the synthesized MOF

through doping potential impurities for intensifying the utilization of visible

light photons.

MOF Intrinsic Characteristics: To analyze the underlying physical

chemistry of the developed MOF photocatalyst.

Solar Energy Driven Photocatalysis: To evaluate solar energy driven

photocatalysis ability of the synthesized MOF by adopting a model

pollutant.

1.4 Report Outline

Chapter 1 describes the sources and effects of chlorophenols to human being and

environment, followed by techniques practiced for disposing them. Background

information on MOF and its prospective as a photocatalyst were discussed in later part

of chapter. The chapter ends with problem statements and objectives of the present

dissertation.

Chapter 2 comprises the detailed literature review on MOF as photocatalyst

materials. In addition, the components in MOF, metal and linker was also reported. The

6

chapter gives particulars on various method used by various researchers to synthesis

MOF along with its applications.

Chapter 3 outlines the detailed synthesis route for MOF followed by modification

methods using different types of metal implemented in the present study. It also

elaborates on the advanced characterization tools adopted for revealing the physical

chemistry nature of the prepared MOF. In the end the chapter provides the details of the

performed photocatalysis experiments and conditions.

Chapter 4 consolidates the significant findings of the present objectives. The

detailed chemistry of the obtained MOF was analyzed and discussed with proper

evidence. The chapter also discusses solar energy driven photocatalytic performances of

the prepared MOFs and proposes the underlying mechanism for the reaction to occur.

Chapter 5 outlines the significant outcome of thesis and recommendation for future

studies.

7

CHAPTER 2: LITERATURE REVIEW

2.1 Metal Organic Frameworks (MOFs) – Photocatalysis

Ever since late 1990’s, Metal Organic Frameworks (MOFs) have been projected as

perspective photocatalysts. According to IUPAC, photocatalysis is defined as “change

in the rate of a chemical reaction or its initiation under the action of ultraviolet, visible,

or infrared radiation in the presence of a substance (the photocatalyst) that absorbs light

and is engaged in the chemical transformation of the reaction partners” (Braslavsky,

2007). In earlier days MOF-photocatalysis research stance on the credence that MOFs

were comparable with classical inorganic semiconductors, possessing extended

structure formed by bridging ligands and metal connecting nodes. The under lying

theory exhibited by MOFs family through utilizing UV-Visible electromagnetic

spectrum as like classical semiconducting photocatalysts transformed them in to

alternative photocatalyst materials (Silva et al., 2010). Their absorption of light is

attributed to either the following; localized ligand-to-metal charge transfer (LMCT),

metal-to-ligand charge transfer (MLCT) transition or a p–p* transition of the aromatic

ligand process (Allendorf et al., 2009).

Recent years researches focusing MOFs based photocatalyst for destruction of liquid

organic pollutants have been reported. Doubly interpenetrated porous MOF [Zn4O (2,6-

NDC)3(DMF)1.5(H2O)0.5]·4DMF·7.5H2O (UTSA-38) with energy gap 2.85 eV was

synthesized for degrading methyl orange (MO). Compared with visible light irradiation,

the decomposition of MO was significantly faster under irradiation of UV light. This

finding showed that photocatalytic reaction of UTSA-38 was more efficient under UV

irradiation, in spite it had lower energy gap. The possible mechanism for it was

proposed by the authors and is illustrated in Figure 2.1. The initial process of MOF

8

(UTSA-38) photocatalysis also starts with the generation of electron– hole pairs, once

the absorption energy is equal or greater than the energy gap of the compound electrons

(e-) present in it gets excited from the valence band (VB) to the conduction band (CB),

leaving the holes (h+) in the VB. The electrons and holes migrate to the surface of the

compound then the photoinduced energy transfers to the adsorbed species: electrons

reduce the oxygen (O2) to (*O2-); in turn, holes oxidize the H2O to *OH. All these

generated Reactive Oxygen Species (ROS) have ability to decompose methyl orange

effectively (Das et al., 2011).

Another series of MOF [Cu(4′-(4-pyridyl)- 4,2′:6′,4″-terpyridine)2Mo4O13]∞ and

[Ni(4′-(4-pyridyl) 4,2′:6′,4″terpyridine)2Mo4O13]∞ was reported by Natarajan and co-

workers and it showed good photocatalytic for degradation cationic and anionic dyes,

methyl orange (MO) and rhodamine B (RhB) respectively. During the photocatalytic

process of polyoxometalate (POM)-based inorganic−organic hybrids UV−Vis light

induces POM/organic ligands (L) to produce oxygen and/or nitrogen−metal charge

transfer with promoting electron from the highest occupied molecular orbital (HOMO)

to the lowest unoccupied molecular orbital (LUMO). The charge transfer excited state

(POM* and/or L*) can be deactivated by oxidizing the contaminant directly, and/or

oxygenating water molecules into the *OH radicals, to complete the photocatalytic

process (Chen et al., 2013).

9

Figure 2.1: Mechanism proposed for MO photodegradation on UTSA-38 activated

under UV and visible light. Source: (Das et al., 2011)

2.2 Design and Synthesis of MOFs

Coordination polymers also known as metal-organic coordination networks

(MOCNs) or metal-organic frameworks (MOFs), are metal-ligand compounds that

extend “infinitely” into one, two or three dimensions (1D, 2D or 3D, respectively) via

more or less covalent metal-ligand bonding (Figure 2.2) (Du et al., 2013; Lin et al.,

2014; Zhu & Xu, 2014).

10

Figure 2.2: Graphic illustration of MOF structure with different dimensionalities.

Donor atoms (E) can be O, N, S, Se etc. Source: (Janiak, 2003)

The structure of MOFs has been compared with aluminosilicate type zeolites,

because they have a similar open network with micro pores (< 2 nm). However, there

are MOFs that have pores in the mesoporous range (2 – 50 nm). The configuration in

which the building blocks of both zeolites and MOFs are bonded is greatly dependents

on the synthesis conditions. For instance, zeolites comprise of corner shared, inorganic,

tetrahedral units of both AlO4 and SiO4. Such structure needs an additional molecule or

ion in the form of solvent to act as a template. These constraints are not applicable for

metal organic frameworks thus making a major difference between them. In general,

the building blocks of MOFs enclose both inorganic and organic components that

enable the connectivity without any templating species. This difference is also important

11

as it means MOFs may include regions of hydrophobic (aliphatic or aromatic areas) or

hydrophilic functions that can affect the adsorption properties of the crystal lattice.

MOFs are constructed via a self-assembly, supramolecular process known as the

“bottom-up” approach. In contrast to supramolecular chemistry, the organic and

inorganic building blocks are covalently bonded, giving rise to structures which have

been shown to be stable up to 500 °C and are chemically resistant to most solvents

(Cavka et al., 2008).

2.2.1 Metal Center

Transition metal ions that possess divalent cations are often used as the inorganic

components of MOFs. The most recent works adopts mostly divalent like manganese

(Dybtsev et al., 2004), iron (Sanselme et al., 2002), cobalt (Livage et al., 2001), nickel

(Guillou et al., 2003), copper (Forster et al., 2002), zinc (An et al., 2009), and cadmium

(Wen et al., 2012). Researches related to trivalent cations are scarce and mostly refer to

vanadium (Barthelet et al., 2003) ,chromium (Surble et al., 2006) and as well as indium

(Lor et al., 2002) for their specified magnetic properties. Likewise, several rare-earth

materials were also studied due to their luminescence properties. Different metal ions

are well known to prefer different coordination numbers and geometries, such as linear,

T- or Y-shaped, tetrahedral, square-planar, square-pyramidal, trigonal-bipyramidal,

octahedral, trigonal-prismatic, and pentagonal-bipyramidal (Table 2.1) (Kitagawa et al.,

2004). For example, Cu (II) ions possess d9

electronic configurations; prefer square-

planar, tetrahedral geometries and occasionally bonds with other coordination numbers,

depending on the choice of ligands and solvents. In addition the ligands also play

significant role in geometry formation and was reported by Cao et al. (2002). In their

study mixture of copper (II) ions and 1, 2, 4, 5-benzenetetra carboxylic acid along with

auxiliary ligand (pyrazine, 4, 4’-bipyridine and hexamethylenetetramine) aligned copper

12

(II) atoms in square pyramidal geometry. However this was achievable when imidazole

was used as ligand. Hence, divalent cations especially cadmium and copper were chosen

in this study. The coordination of the connector and linker along with functional site is

shown in table 2.1.

Table 2.1: Coordination environment of components in MOFs Source: (Kitagawa et

al., 2004)

Number of

functional

sites

Connector Linker

2

3

4

5

6

13

2.2.2 Organic Linkers

The design and synthesis of MOFs arise with the choice of the metal as the nodes of

structure and bridging organic spacers. The structure and functionality rely on either of

the two components or on the nature and diversity of bonding between them (O’Keeffe

et al., 2008). Theoretically, utilization of geometrically rigid organic building blocks

allows targeting of frameworks with definite topologies (Janiak, 2003). These

frameworks generally exhibit comparatively high thermal and mechanical stability as

well as capable of retaining the porosity upon exit of guest solvent (Lin et al., 2014).

The linkers can be electrically neutral, anionic, or cationic and is shown in Figure

2.3. Neutral organic linkers such as pyrazine and 4,4’-bipyridine (bpy) are useful as

pillars in the construction of pillared-layer in 3D networks (Chen et al., 2013; Song et

al., 2012). The most widely used anionic linkers are carboxylates because they have the

ability to aggregate metal ions into clusters and thereby form more stable frameworks

(Wen et al., 2009). A new MOF namely {[Cd2(TZ)3(BDC)0.5]·5H2O}n was synthesized

with 1H-tetrazole and 1,4-benzenedicarboxylic acid demonstrated robust thermal

stability up to 290oC (Zhong et al., 2011). Cationic organic ligands are rare choice,

owing to their low affinities for cationic metal ions (Zhang et al., 2013). Therefore, rigid

benzene di-, tri-, as well as tetra-carboxylic acids, azolate-based ligands, their

derivatives are usually utilized as organic building blocks (Lin et al., 2014). When

compared to bidentate N-donor linkers, the ability of the planar sp2 hybridized

carboxylate groups to chelate metal ions in different ways (Figure 2.4) and rotation

around the C-C bond gives polycarboxylates more flexibility thus generate variety of

coordination modes (Long, 2010). Shen et al. (2012) were successfully synthesized new

MOF with chiral nano-pores by spontaneous resolution from chiral components of 2,2’-

bipyridine-5,5’-dicarboxylate (BPDC). New cobalt 1,3,4-benzenetricarboxylate

(trimesic acid) coordination polymers were synthesized and connection of sinusoidal

14

chains of cobalt octahedra by two types of trimesate ions resulted in a three-dimensional

network with pentahydrated channels (Livage et al., 2001). Therefore, carboxylate

based linkers was apposite linkers to synthesize high thermal stability metal organic

frameworks. All their synthesis follows different routes and was consolidated in the

following section.

Figure 2.3: Different types of linkers used in MOFs.

Source: (Livage et al., 2001).

15

Figure 2.4: Six different coordination modes of carboxylate ligands.

Source: (Long, 2010)

2.3 Synthesis Methods

Over years slow evaporation method is a most common methods for crystallization

was employed for preparing MOF crystals (Dey et al., 2014). However, this method

requires long reaction time from several hours to days compared with other

conventional methods.

Therefore, routine synthesis of MOFs involves solvothermal, hydrothermal,

microwave-assisted synthesis, electrochemical synthesis, sonochemical along with

mechanochemical synthesis have been applied as alternatives for MOF synthesis. Table

2.2 Summarizes the diverse method practiced in synthesizing MOFs. Furthermore,

alternative routes can lead to compounds with different particle sizes, distributions and

morphologies that influence the material’s properties (Stock & Biswas, 2011).

16

Table 2.2: Summary of various methods in synthesis of MOFs

MOF Method Conditions References

M-BTB

M= Al, Cr, Fe, Ga

Solvothermal MOFs with combination

of trivalent metals and

BTB using DMF were

synthesized at 80oC, 90

oC

and 100oC for 24 h

respectively.

(Saha et al.,

2011)

[Ce(L)(DMF)]·2.5(D

MF)·3(H2O)]n

Solvothermal A new lanthanide metal

organic framework was

synthesized in the

presence of DMF heated at

130oC for 3 days.

(Chen et al.,

2011)

[Cd(dptz)2]·{Cd[(NH2

)2CS]4}·(NO3)4

Cd(dpmtz)2

Solvothermal Cadmium based MOF was

prepared under

solvothermal condition

100 °C-120 °C for 72 h.

(Liu et al.,

2014b)

[Cd3(IDC)(BDC)1.5(H2

O)]n

Hydrothermal Two mixed-linker MOF

was synthesized at 170oC

for 4 days. The

synthesized exhibited 3D

pillared-layered structure.

(Lu et al.,

2012)

[(Ce(oda)3Zn1.5(H2O)3

)∙0.75H2O]n

Hydrothermal Heterometallic MOF

Zn(Ac),Ce2O3 was

obtained at 160oC for 3

days.

(Wang et al.,

2010)

IRMOF1,

IRMOF2,IRMOF3

Microwave-

assisted

Isoreticular MOF known

as IRMOF1, IRMOF2,

IRMOF3 were

successfully prepared

through microwave

heating at 150 W for 25 s,

40 s and 35 s respectively.

(Ni & Masel,

2006)

17

Table 2.2, continued

MOF Method Conditions References

[Cu3(BTC)2(H2O)3]

[Cu2(OH)(BTC)(H2O)

]2nH2O

Microwave-

assisted

Two Cu based new MOF

was achieved by applying

microwave at 140oC for 60

min and 170oC for 10 min

with 300 W.

(Seo et al.,

2009)

Cu3(BTC)2 Electrochemical 3D structured of CuBTC

was obtained with 100 mA

current in 0.05 M of

NaNO3for 10 min.

(Nguyen et al.,

2016)

MOF-177

Sonochemical MOF-177, formulated as

Zn4O(BTB)2 (BTB was

prepared by ultrasound

assisted chemical method

with power output of 500

W at 20 kHZ, 60% of

power level in 40 min.

(Kim et al.,

2011)

MOF-5 Sonochemical Sonochemical method was

used in the synthesis of

MOF-5 with following

conditions: Maximum 200

W at 20 kHZ), 50% of

power level in 30 min.

(Son et al.,

2008)

[Cu(INA)2] (INA=

isonicotinate)

Mechanochemical 3D microporous MOF was

synthesized by grinding

copper acetate together

with isonicotinic acid at

oscillation rate at 25 Hz

for 10 min.

(Pichon et al.,

2006)

18

Table 2.2, continued

MOF Method Conditions References

[Zn2(bdc)2(dabco)] Mechanochemical A mixture of ZnO, H2bdc,

dabco were mixed with

grinding liquid (DMF) and

ground for 20-60 min in

grinder mill at 30 Hz.

(Friscic et al.,

2010)

2.3.1 Hydrothermal and Solvothermal Synthesis

Hydrothermal is a synthesizing process of crystal that depend on the solubility of

minerals in high-temperature and vapor pressure whereas solvothermal techniques are

time-consuming method carried out in closed vessel under autogenous pressure above

the boiling point of solvent (Demazeau, 2008). The most commonly used organic

solvents are dimethyl formamide, diethyl formamide, acetonitrile, acetone, ethanol,

methanol etc.

Mixtures of solvents have also been used to tune the solution polarity and the

kinetics of solvent-ligand exchange affecting crystal growth (Dey et al., 2014).

Solvothermal reactions can be carried out in different temperature ranges, depending on

the constraint of the reaction. Commonly, glass vials are used for lower temperature

reactions while reactions performed at temperatures higher than 400 K required Teflon-

lined autoclaves (Wang & Ying, 1999). As a result, simple and time consuming method

were key factors that hydrothermal and solvothermal method were used for synthesizing

of MOFs in this study.

19

2.3.2 Microwave Synthesis

Microwave-assisted synthesis is a process involving heating a solution with

microwave for an hour to produce nano sized crystals (Dey et al., 2014). Microwave

assisted synthesis depends on the interaction of electromagnetic waves with mobile

electric charges. These can be polar solvent/ions in a solution or electrons/ions in a

solid. In the solid, an electric current is formed and heating is due to electric resistance

of the solid. In solution, polar molecules try to align themselves in an electromagnetic

field and in an oscillating field so that the molecules change their orientations

permanently. Hence, applying the appropriate frequency aids collision between the

molecules where by increases the kinetic energy, i.e., temperature, of the system.

(Klinowski et al., 2011). The advantage of this method is fast, simple, energy and time

efficient (Lagashetty et al., 2007).

2.3.3 Electrochemical Synthesis

Electrochemical synthesis is a process that does not require metal salts and offers

continuous production of MOF crystals, which is a major advantage in an industrial

process. Rather than using metal salts, the metal ions are continuously introduced

through anodic dissolution into synthesis mixtures that include organic linkers and

electrolytes (Joaristi et al., 2012). The benefits of using electrochemical method are the

possibility to run continuous process and obtain higher solid content compared to

normal batch reactions (Stock & Biswas, 2011).

2.3.4 Sonochemical Synthesis

Sonochemistry is a phenomenon by which molecules undergo chemical change due

to the application of intensive ultrasonic radiation (20 kHz–10MHz) (Aslani & Morsali,

20

2009; Gedanken, 2004). In sonochemical synthesis, the major energy transfer

mechanism is acoustic cavitation process involving the formation, growth and

instantaneous collapse of bubbles in a liquid, which creates short lived local hot spots

with high temperature and pressure, as well as fast heating and cooling rates

(Dharmarathna et al., 2012; Jung et al., 2010). Sonochemical methods can generate

homogeneous nucleation centres and form crystal in shorter time compared to

conventional hydrothermal methods (Son et al., 2008). MOF-5 synthesis using

sonochemical irradiation in 1-methyl-2-pyrrolidinone (NMP) can produce 5–25 mm

crystals in 30 min, which is similar to MOF-5 synthesized via solvothermal or

microwave methods (Son et al., 2008). There are several of parameters that regulate the

formation of cavities and the intensity of their collapse, and only a fraction of the input

energy is transformed into cavitation. Besides the acoustic frequency and intensity

(based on the equipment used), parameters such as the choice of liquid (vapor pressure,

viscosity, and chemical reactivity), the temperature and the gas atmosphere play an

important role (Kim et al., 2011). Volatile organic solvents are often not an effective

medium for sonochemistry because the high vapor pressure reduces the intensity of

cavitational collapse and hence the resulting temperatures and pressures (Son et al.,

2008).

2.3.5 Mechanochemical Synthesis

It is solvent-free synthesis method, construction of bonds take place through simple,

economical and environmentally friendly prompt mechanochemical method (Dey et al.,

2014). Mechanical force induces many physical phenomena (mechanophysics) as well

as chemical reactions (Bertran, 1999; Boldyrev & Tkacova, 2000). Mechanical

breakage of intramolecular bonds followed by a chemical transformation takes place

21

during mechanochemical synthesis (Boldyrev & Tkacova, 2000). They exhibit short

reaction time in the range between 10 min and 60 min with quantitative yield of small

sized particles (Garay et al., 2007).

Instead of using metal salts as starting materials, researchers are exploring the use of

metal oxides as precursor for synthesis of MOF results in formation of water as side

product. For example, ZnO has been shown to be suitable precursor for synthesis of

pillared-layered MOFs or ZIF (Friscic & Fabian, 2009; Yuan et al., 2010). In contrast,

metal oxides are rarely used in solvent based reactions due to their low solubility (Stock

& Biswas, 2011).

2.4 Other Application

2.4.1 Gas Storage

Gas storage in MOFs has been widely explored in the past decade and researchers

actively seeking suitable frameworks to efficiently store various gases such as hydrogen

(Foy et al., 2006), methane (Eddaoudi et al., 2002; Gandara et al., 2014) and carbon

dioxide (Beldon et al., 2010; Sumida et al., 2011).

The large surface area, tailorable pore environments, functionalized polar group

coupled with good chemical and thermal stability made MOFs attractive for gas storage

and separation (Dey et al., 2014). The US Department of Energy (DOE) had set their

targets for hydrogen storage system of 0.055 kg/kg for years 2017 and the detailed

information pertaining to it is tabled in Table 2.3 (Klebanoff, 2012).

Foy et al. (2006) demonstrated that IRMOF-20 are constructed from [Zn4O] clusters

and 4,4’,4”-benzene-1,3,5-trityltribenzoate (BTB). Due to its high BET surface area

(~5000m2

g-1

) and large pore volume (1.59 cm3

g-1

), the H2 uptake value of IRMOF-20

22

is 7.5 wt% at 70 bar and 77 K which exceeds that of any other porous material.

Comparatively, MOF-5 is reported to reach 4.5 wt% of H2 uptake at 78K. However, at

room temperature, poor uptake was recorded for IRMOF-20 (1.0 wt% at 20 bars)

because of low interaction energy between the framework and physisorbed H2 (Frost et

al., 2006; Rosi et al., 2003). To overcome this problem, researchers found that MOFs

open metal sites provides high surface area which facilitates stronger interaction

between the metal ions nodes and H2 molecules. Moreover, doping MOFs with metal

ions might improve H2 uptake activity (Dey et al., 2014; Han & Goddard, 2007).

Several examples of methane and carbon dioxide gas adsorption on metal organic

framework have been reported. Gandara et al. (2014) utilized two aluminum metal

organic frameworks, MOF-519 and MOF-520 to measure methane uptake capacity.

Both materials exhibit permanent porosity and high methane volumetric storage

capacity. At 298K, MOF-519 has volumetric capacity of 200 and 279 cm3cm

-3 at 35 and

80 bar respectively and MOF-20 has volumetric capacity of 162 and 231 cm3cm

-3 under

same conditions (Gandara et al., 2014). Mostly, CO2 storages are influenced by surface

area. High surface areas of metal organic frameworks provide large CO2 adsorption

capacities due to the efficient packing and close approach of the guest molecules on the

pore surface (Beldon et al., 2010; Sumida et al., 2011). MOF-177 show very high

storage density of carbon dioxide 320cm3(STP)/cm

3 at 35 bar,

which is approximately 9

times higher than the quantity stored at this pressure in a container without the metal–

organic framework and is higher than conventional materials used for such an

application, namely, zeolite 13X (Millward & Yaghi, 2005).

23

Table 2.3: DOE targets for on-board hydrogen storage system.

Source (Dey et al., 2014; Han & Goddard, 2007)

Storage parameter Units 2010 2017

System Gravimetric

Capacity (net useful

energy/max. system

mass)

kg H2/kg system 0.045 0.055

System Volumetric

Capacity (net useful

energy/max. system

volume)

kg H2/kg system 0.028 0.040

Min/max. delivery

temperature

oC -40/85 -40/85

Cycle life (1/4 tank

to full)

Cycles 1000 1500

Max. delivery

pressure from

storage system

atm (abs) 100 100

System fill time (for

5 kg H2)

min 4.2 3.3

2.4.2 Sensing

In the past years, luminescent MOFs have been widely explored for diverse

applications in chemical sensors (Luo & Batten, 2010) , light emitting devices (Guo et

al., 2010; Liu et al., 2010) and biomedicine (Rieter et al., 2007; Rowe et al., 2009).

There are two basic types of luminescence; first is fluorescence, which is spin-allowed

and has typical lifetimes on several nanoseconds. The second is phosphorescence which

is spin-forbidden and has lifetimes that can be as long as several seconds (Allendorf et

al., 2009).

MOFs with multiple luminescent centres are very fascinating as multifunctional

luminescent materials because their luminescence properties can be systematically

tuned by deliberate use of organic ligands and metal ions. That is, both the organic

24

ligands with aromatic moieties or conjugate π systems and metal components,

especially for various lanthanides and inorganic clusters, can provide platforms for

generating luminescence. In addition, some guest molecules or units (lanthanide ions,

dye molecules, chromophores, etc.) within porous MOFs can also contribute to the

luminescence. This phenomenon is schematically illustrated in Figure 2.5. Eu and Tb

are most attractive lumophores because of their narrow emission (Cui et al., 2012;

Reddy & Sivakumar, 2013; Zhao et al., 2016). Metal-based luminescence usually

involves lanthanide complexes and rare earth metals that are sensitized by a LMCT-type

process (Allendorf et al., 2009).

Figure 2.5: Illustration of emission possibilities in a porous MOF. Metal groups

(blue octahedra) are linked by organic linkers (yellow rectangles) with an incorporated

guest (green circle). Source: (Allendorf et al., 2009).

25

2.4.3 Catalysis

MOFs possess uniform, continuous and permeable channels, they can provide active

sites on the pore surface and transport reactants/products to or from inner reactive

vessels (such as cage-like cavities inside the MOFs) (Liu et al., 2014a). Catalytic

applications of MOFs are subdivided into four classes according to the catalytic sites:

Coordinatively unsaturated metal sites (CUMs), metalloligands, functional organic sites

(FOS) as well as metal nanoparticle (MNPs) embedded in the framework cavities

(MNPs@MOFs).

The introduction of CUMs into porous MOFs is very favorable as former can interact

strongly with organic molecules in catalysis. For example, Horike et al. (2008)

successfully prepared Mn3[(Mn4Cl)3BTT8(CH3OH)10]2 which can catalyze the

transformation of selected aldehydes and ketones with cyanotrimethylsilane to the

corresponding cyanosilylated product. The transformation is catalyzed by unsaturated

Mn2+

ions in the framework that act as Lewis acid catalysts and lead to high yield

product. Chromium based metal-organic framework (MIL-100) was synthesized and has

high catalytic activity in the cyanosilylation reaction. The pseudo-octahedral chromium

was accessible for potential reactant when the coordinated water molecules are removed

in vacuum or at elevated temperature (Henschel et al., 2008).

Metalloligand-based MOFs can functionalize as heterogenous asymmetric catalyst

with higher catalyst loading and more accessible catalytic centers. A series of Ru-/Mn-

/Co-porphyrin complexes have displayed excellent activities in asymmetric epoxidation,

cyclopropanation and aziridination of olefins, as well as C–H bond activation of carbon

hydrogens (Feng et al., 2012; Shultz et al., 2009; Wang et al., 2012b; Xie et al., 2011).

MOFs containing chiral metallosalen building blocks have attracted a great deal of

recent interest. A few chiral metallosalen-based MOFs have been studied in asymmetric

catalytic reactions. For example, Hupp’s group prepared chiral MOFs based on Mn-

26

salen derived biphenyldicarboxylate (bpdc) or tetrakis(4-carboxyphenyl)benzene (tcpb)

ligands and demonstrated their asymmetric catalytic activity in epoxidation of olein

(Cho et al., 2006).

Reports on proof of concept with regard to the catalytically-active functional organic

sites (FOS) in MOF catalysis are limited. Three types of approaches have been used by

researchers to construct catalytic MOFs based on organic functional groups. There are

introduction of FOS in the organic linkers, grafting of FOS groups on the coordinatively

unsaturated metal centers, and post-covalent modification of organic ligands or linker

sites. Besides functioning as catalyst MOFs containing FOS can be used to immobilize

catalytic metal complexes through complexation (Bloch et al., 2010; Crespo et al., 2011;

Hwang et al., 2008; Nguyen et al., 2012).

The doping of MOFs with metal nanoparticles (MNPs) is advantageous for

heteregenous catalysis. So far, a few catalytically active metals (e.g. Cu, Ru, Au, Pd, Pt)

have been finely dispersed into the MOF cavities. Haruta’s group successfully

developed method for deposition of Au into MOFs such as CPL-1, CPL-2, MiL-53 (Al),

MOF-5 and HKUST-1 by solid grinding process with volatile organogold complex,

Me2Au(acac) (Ishida et al., 2008).

The complied literatures clearly elucidate the limitation of studies pertaining to the

implementation of MOF as an alternative to conventional photocatalyst (as discussed in

section 2). However there were some attempts by limited research groups but their

focus was motivated on the utilisation of shorter wavelength. Owing to the limited

availability of these wavelengths in the natural light the present study focused on

developing novel visible light active MOFs.

27

CHAPTER 3: METHODOLOGY

3.1 Materials

Cadmium (II) nitrate tetrahydrate (Cd(NO3)2.4H2O, 98 %), 1,2,4,5-

benzenetetracarboxylic acid (H4btec, 96 %), N,N-Dimethylformamide (DMF, 99.5 %),

indole-3-Carboxaldehyde azine (bimb) and 2-chlorophenol (2-CP, 99 %) were

purchased from Sigma Aldrich. Silver nitrate (AgNO3, 99%, Friendemann Schmidt),

sodium hydroxide (NaOH), Iron (III) nitrate nonahydrate (Fe(NO3)3.9H2O, 99 %), zinc

(II) nitrate hexahydrate (Zn(NO3)2.6H2O) and copper (II) nitrate trihydrate

(Cu(NO3)2.3H2O, 99 %) were purchased from R&M Chemical while Sulphuric Acid

(H2SO4, 98%) was purchased from Merck. The AEROXIDE® P25 was obtained from

Evonik Industries AG, Germany. All chemicals and solvents were used without further

purification.

3.2 Synthesis of Cd-MOF

In the typical synthesis, mixture of Cd(NO3)2.4H20 (0.1 mmol / 0.031g), H4btec (0.1

mmol / 0.025g), NaOH (0.2 mmol / 0.008g), and 15 ml of de-ionized water was stirred

for 20 min. The mixture was transferred into Teflon-lined stainless steel vessel and then

the vessel was sealed and heated at 180 °C for 48 h. After slowly cooling at room

temperature, colorless needle shaped crystal as illustrated in Figure 3.2 was obtained by

centrifuge at 15 000 rpm for 20 min and washed with distilled water to remove traces

linker. The reaction involved in the synthesis of Cd-MOF was schematically depicted

in Figure 3.2.

28

Figure 3.1: Flowchart proposed approach in synthesis of new metal organic

frameworks.

Characterization

Single Crystal XRD

Powder XRD

Field Emission Scanning Electron

Microscopy (FESEM)

Fourier Transform Infrared Spectroscopy

(FTIR)

Thermogravimetric Analysis (TGA)

Ultraviolet-visible Spectroscopy (UV-Vis)

Photoluminescence (PL)

X-ray Photoelectron Spectroscopy (XPS)

Application

Solar Photocatalysis Experiment

Synthesis of Metal Organic Framework

Synthesis of Cd-MOF Synthesis of Cu-MOF

Intercalation of Metal

Ions into Cd-MOF

29

Figure 3.2: Photograph synthesized Cd-MOF and schematics of reaction involved in

the synthesis.

3.2.1 Intercalation of Metal Ions into Cd-MOF

Metal ion intercalated metal organic framework were prepared according to the

previous report (Xu et al., 2014b). 0.12g of as prepared Cd-MOF was dispersed in 15

mL 0.01 M solution of Fe(NO3)3.9H2O, [Zn(NO3)2.6H2O] and Ag(NO3) respectively

through an ion-exchange reaction. The reaction mixture is stirred for 24 h at room

temperature yields powder, were washed repeatedly with distilled water and dried in

oven at 60 °C for 12 h. Thus, obtained samples were labeled as Ag-Cd-MOF, Fe-Cd-

MOF and Zn-Cd-MOF respectively. The snap shots of the prepared intercalated Cd-

MOF are portrayed in Figure 3.3.

30

Figure 3.3: Snap shots of (a) Ag-Cd-MOF, (b) Fe-Cd-MOF and (c) Zn-Cd-MOF (d)

Cu-MOF.

3.3 Synthesis of Cu-MOF

Cu-MOF was prepared by mixing the precursor Cu(NO3)2.3H20 (0.1 mmol / 0.024g),

with linker H4btec (0.1 mmol / 0.025g), bimb (0.1 mmol / 0.029g) and NaOH (0.2 mmol

/ 0.008g) 15 ml as solvent (DI water/DMF = 1/1 : v/v). The prepared mixture was

placed in a Teflon-lined stainless steel autoclave and heated at 180 °C for 48 h. The

reacted mixture is allowed cool until it reaches room temperature. The obtained black

colour product (Figure 3.3 d) was washed with distilled water to remove traces of

linkers.

a) b)

c) d)

31

3.4 Characterization

The powder XRD data were collected on PANalytical, EMPYREAN diffractometer

with Cu Kα radiation (λ = 1.5418 Å) over the 2θ range of 5−60° at room temperature.

The crystallite size of Cd-MOF was calculated by using Scherrer equation shown below

(Xu et al., 2014b):

(3.1)

Where D is the crystallite size (Ghorai), K is the shape constant (0.9), λ is the

wavelength of Cu Kα radiation (1.5406 Å), β is full width at half maximum and θ is the

diffraction angle (o).

The solid-state diffuse-reflectance UV/Vis spectra for powder samples were recorded

on a Shimadzu UV-2600 UV–Vis spectrophotometer equipped with integrating sphere

and using BaSO4 as a standard. The powder sample was filled evenly up to the upper

surface of the powder sample holder’s hollow. Glass rod was used for compacting and

pressing the powder in the sample holder.

The optical diffuse-reflection spectra of MOFs were measured using Kubelka–Munk

function (Equation 3.2 and 3.3) (Kan et al., 2012; Leong et al., 2014).

( ) ( )

(3.2)

( )

(3.3)

Where R is the diffused reflectance of at the given wavelength, where h is the

Planck’s constant (6.626 × 10-34

J s), C is the speed of light (3.0 108 ms

-1) and λ is the

wavelength (Ghorai).

Thermogravimetric analyses were performed on a simultaneous STA 449 F3 Jupiter,

Netzsch thermal analyzer under flowing protective as well as N2 as purge gas with flow

32

rate of 20 ml/min and 50 ml/min respectively with heating rate of 10 °C/min between

ambient temperature and 700 °C.

Infrared (IR) samples were prepared as KBr pellets, and spectra were obtained in the

4000–400 cm-1

range using a Spectrum 400 FTIR, Perkin Elmer spectrophotometer.

A micro-PL/Raman spectroscope with the excitation wavelength 325 nm (Renishaw,

inVia Raman Microscope) was used to acquire the photoluminescence spectra.

X-ray photoelectron spectroscopies (XPS) of synthesized samples were measured

with the EnviroESCATM

at Specs GmbH, Berlin with a scan range of 0–1200 eV

binding energy. The collected high-resolution XPS spectra were analyzed using

CasaXPS peak fitting software. The carbon C 1s line at 284.8 eV was taken as a

reference for surface-charging corrections.

3.4.1 Single Crystal Structure Determination

Suitable single crystals was carefully selected under an optical microscope and glued

to thin glass fibers. Intensity data were collected on a Bruker Smart APEX II CCD

diffractometer with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) at room

temperature. Empirical absorption corrections were applied using the Olex2 program

(Dolomanov et al., 2009). The structures were solved by direct methods and refined by

the full-matrix least-squares based on F2 using the SHELX program (Sheldrick, 2008).

All non-hydrogen atoms were refined an isotropically and the hydrogen atoms of

organic ligands were generated geometrically.

3.5 Solar Photocatalysis Experiment

The solar photocatalytic potential of the synthesized MOFs was evaluated by

mineralizing non-photosensitizing, Endocrine Disruptive recalcitrant compound 2-

33

chlorophenol as model pollutant. All the experiments were executed in a simple batch

reactor of 500 mL under stirred condition in presence of aqueous solution of 2-

chlorophenol (10 mg/L) containing 180 mg of respective MOF. Prior to the solar

photocatalysis dark reactions was performed for 24 h to ensure the adsorption

equilibrium. The graphical illustration of the solar photocatalysis experiment is shown

in Figure 3.3. All the solar experiments were conducted under clear sky condition at

University of Malaya, Kuala Lumpur between 10.00 am and 4.00 pm. During the solar

light photocatalytic experiments, solar light intensity was measured using LT Lutron

LX-101 Lux meter and the average light intensity under clear sky condition was found

to be 70 940 to 98 000 lux. The effect of pH on 2-chlorophenol degradation experiment

was carried out by adjusting the pH using NaOH (0.1M) and H2SO4 (0.1M). The aliquot

was drawn at regular intervals, centrifuged and the permeated was analysed for residual

concentration of 2-cholorophenol with ultra-performance liquid chromatography

(UPLC) (ACQUITY UPLC H Class, Waters) equipped with C18 column (50 mm × 2.1

mm × 1.7 μm). Acetonitrile (ACN) and water in the ratio 60:40 was flushed as mobile

phase with a flow rate of 0.4 mL min-1

at =285 nm. To test the reusability of

photocatalyst, the synthesize MOFs were reused thrice in the photodegradation

experiments. Control experiments were carried under the solar irradiation but in the

absence of MOFs. The calibration curve adopted for quantification of 2-chlorophenols

is presented in Figure 3.4

The 2-CP photodegradation followed the first order kinetics model as shown in

Equation 3.4.

(3.4)

34

Wherein C0 is the initial 2-CP concentration, C is the 2-CP concentration at a certain

time, t is the reaction time, and k is the kinetic rate constant. The values of k can be

calculated from the slope and the intercept of the linear plot (Wen et al., 2012)

Figure 3.4: Graphical illustration of adopted solar photocatalysis experiment.

Figure 3.5: Calibration curve for 2-chlorophenol.

2-CP (10mg/L)

Catalyst

solar light intensity 70 940 ~ 98 000 lux

0 5 10 15 20 25 30

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

Are

a

Concentration (mg/L)

y=132 002x + 28 727

R2= 0.998

35

CHAPTER 4: RESULTS AND DISCUSSION

4.1 Inherent Physical-Chemistry of Cd-MOF and Metal Ions Intercalated Cd-

MOF

Single crystal X-ray analysis on crystal acquired discovered that Cd-MOF

crystallizes in triclinic system with group Pī (Table 4.1). As shown in Figure 4.1, the

metal Cd (II) ion is six-coordinated with two oxygen atoms from two carboxylate

groups of two different btec4-

linkers and four coordinated water molecule resulting in

slightly distorted octahedral coordination geometry. The (O3 and O1) atoms comprise

the equatorial plane and (O (11), O5, O6 and O7) occupy axial positions. The Cd-O

bond length vary from 2.236(3) Å to 2.371 (4) Å are comparable wih the corresponding

values reported for Cd-carboxylic complexes (Table 4.2) (Wang et al., 2012a). The

carboxylate groups present in the H4btec linker are deprotonated and was confirmed by

the IR spectrum with no absorption peak ~1730 cm-1

, a usual wave number for the

protonated carboxylic acid group (Cao et al., 2002).

36

Table 4.1: Single crystal profile extracted for Cd-MOF.

Cd-MOF

Empirical formula H7O7CdC5

Formula weight 291.51

Temperature/K 100.01(10)

Crystal system triclinic

Space group P1

a/Å 5.5108(7)

b/Å 7.8194(10)

c/Å 9.6854(11)

α/° 109.785(11)

β/° 104.283(11)

γ/° 98.964(10)

Volume/Å3 367.24(8)

Z 2

ρcalcmg/mm3 2.636

m/mm-1

2.979

F(000) 282

2Θ range for data

collection

5.74 to 55°

Index ranges -7 ≤ h ≤ 7, -10 ≤ k ≤ 10, -12 ≤ l ≤

10

Reflections collected 2913

Independent reflections 1682[R(int) = 0.0331]

Data/restraints/parameters 1682/0/122

Goodness-of-fit on F2 1.206

Final R indexes [I>=2σ (I)] R1 = 0.0304, wR2 = 0.0785

Final R indexes [all data] R1 = 0.0317, wR2 = 0.0794

Largest diff. peak/hole / e

Å-3

0.72/-1.24

37

Cd

Cd1

Cd

Cd

Cd

Cd

O

O

O2

O4

O2

O4

O

O

O11

C2

C1

C3

O3

O7

O5

O6

O5

O6

O1

O3

O1

C2

C3

C1

O11 C4

C5

a)

b)

38

Figure 4.1: (a) The coordination environment of Cd (II) ion in Cd-MOF matrix and

its (b-c) 3D network.

c)

39

Table 4.2: Selected bond and angles in Cd-MOF extracted from Single crystal XRD.

Bond Distance (Å) Bond Distance (Å)

Cd(1)-O(1) 2.324(3) O(3)-C(52) 1.275(6)

Cd(1)-O(11) 2.340(3) O(4)-C(5) 1.251(5)

Cd(1)-O(3) 2.236(3) C(1)-C(2) 1.410(6)

Cd(1)-O(5) 2.371(4) C(1)-C(3) 1.388(6)

Cd(1)-O(6) 2.280(3) C(1)-C(4) 1.508(6)

Cd(1)-O(7) 2.346(3) C(2)-C(33) 1.399(6)

O(1)-Cd(11) 2.340(3) C(2)-C(5) 1.494(6)

O(1)-C(4) 1.271(5) C(3)-C(23) 1.399(6)

O(2)-C(4) 1.253(5) C(5)-O(32) 1.275(6)

Angle (°) Angle (°)

O(1)-Cd(1)-O(11) 73.94(12) C(4)-O(1)-Cd(1

1) 136.4(3)

O(1)-Cd(1)-O(5) 76.18(13) C(4)-O(1)-Cd(1) 109.3(3)

O(11)-Cd(1)-O(5) 86.59(14) C(5

2)-O(3)-Cd(1) 112.0(3)

O(11)-Cd(1)-O(7) 171.36(11) C(2)-C(1)-C(4) 123.8(4)

O(1)-Cd(1)-O(7) 112.80(11) C(3)-C(1)-(C2) 119.5(4)

O(3)-Cd(1)-O(1) 87.11(11) C(3)-C(1)-C(4) 116.7(4)

O(3)-Cd(1)-O(11) 84.52(12) C(1)-C(2)-C(5) 121.8(4)

O(3)-Cd(1)-O(5) 162.71(14) C(33)-C(2)-C(1) 118.5(4)

O(3)-Cd(1)-O(6) 114.07(13) C(33)-C(2)-C(5) 119.7(4)

O(3)-Cd(1)-O(7) 90.33(12) C(1)-C(3)-C(23) 122.0(4)

O(6)-Cd(1)-O(1) 151.68(12) O(1)-C(4)-C(1) 119.6(4)

O(6)-Cd(1)-O(11) 88.96(11) O(2)-C(4)-O(1) 121.9(4)

O(6)-Cd(1)-O(5) 80.50(13) O(2)-C(4)-C(1) 118.1(4)

O(6)-Cd(1)-O(7) 86.81(12) O(32)-C(5)-C(2) 116.8(4)

O(7)-Cd(1)-O(5) 100.12(15) O(4)-C(5)-O(32) 123.8(4)

Cd(1)-O(1)-Cd(11) 106.06(12) O(4)-C(5)-C(2) 119.4(4)

Symmetry transformation 1-X,1-Y,-Z;

2-1-X,1-Y,-Z;

3-X,1-Y,1-Z

40

Figure 4.2 (a-b) illustrates the phase purity and crystallinity of the pure Cd-MOF and

was confirmed by a direct comparison between the powder diffraction pattern and a

simulation based on the single-crystal X-ray diffraction. Powder XRD resulted in a

strongest peak at 38.6° corresponding to the (1 0 1) plane of cadmium (ICDD no. 05-

0640)(Malandrino et al., 2005). The as synthesized materials exhibited similar XRD

peak with simulation peak derived from single crystal X-ray diffraction indicated that

the synthesized material and as-grown crystals were homogenous (Surib et al., 2017).

The crystallite size of cadmium based MOF was calculated using Scherrer equation was

75.06 nm. The similar crystallographic pattern for Ag+, Fe

2+ and Zn

2+ intercalated Cd-

MOF is presented in Figure 4.2 (c-e). The diffraction pattern of Cd-MOF intercalated

with different metal ions showed approximately similar pattern as that of pure Cd-MOF

at the diffraction angles of 10.4°, 19.23°, 20.7°, 31.2°, 35.9°, 38.6°, and 39.7°. There

was slight peak shift was experienced by the metal ions intercalated Cd-MOF

compared to the pure was a probable consequence of the disorder in the crystal structure

(Zhou et al., 2013). New and distinctive peaks at 12.9°, 31.4°, and 38.8° were observed

in the diffraction pattern of the intercalated Cd-MOF due to the interaction of metal ions

with the Cd-MOF or the organic linker via π-complexation or a chelation process

(Ebrahim, 2013). The peaks of Fe-Cd-MOF and Zn-Cd-MOF are shifted to the higher

degree region and are clearly seen from Figure 4.3. This shift in peak substantiate the

stocking of Fe3+

and Zn2+

into the crystal lattice of MOF owing to their smaller ionic

radii ( Fe3+

= 0.65 Å; Zn2+

= 0.74 Å) than Cd2+

(0.97 Å). The stocking leads to

subsequent shrinking of the unit cell distinctly and shifted the higher angle (Nagaveni et

al., 2004).

41

Figure 4.2: (a) Powder XRD pattern of cadmium based MOF, (b) Simulated based

on crystal information’s obtained from single crystal diffraction and (c-e) powder XRD

of metal ions intercalated Cd-MOF.

(a)

(b)

(c)

(d)

(e)

Inte

nsi

ty (

a.u

)

PXRD

SXRD

42

Figure 4.3: Powder XRD pattern of pure Cd-MOF and metal ions intercalated Cd-

MOF in (0 0 3) direction.

The morphology and topography of all the synthesized MOFs were investigated

using Field Emission Scanning Electron Microscope (FESEM) and the obtained images

where depicted in Figure 4.5(a-d). The captured image showed prism like structure for

Cd-MOF. However, the metal ion-intercalated samples showed slightly irregular shaped

particles distributed throughout. Consequently, it can be deduce that the intercalation of

metal ions into Cd-MOF result in changing of size and morphology of MOF by shifting

the growth kinetics (Dutta et al., 2017)

10.0 10.2 10.4 10.6 10.8 11.0

Cd-MOF

Ag-Cd-MOF

Fe-Cd-MOF

Inte

nsity (

a.u

)

2

Zn-Cd-MOF

43

a)

b)

44

Figure 4.4: Morphology of (a) Cd-MOF, (b) Ag-Cd-MOF, (c) Fe-Cd-MOF and (d)

Zn-Cd-MOF obtained under different magnification.

c)

d)

45

The functional groups present in the synthesized samples were shown in Figure 4.6.

The spectrum shows a strong broad band at 3000 cm-1

for all the samples (Cd-MOF,

Ag-Cd-MOF, Fe-Cd-MOF and Zn-Cd-MOF) and is assigned to the O–H stretching

vibration of water molecule. The expected characteristic bands of carboxylate groups

were shown at 1557 cm-1

for antisymmetric stretching vibrations νas(COO-) and 1387

cm-1

for symmetric stretching vibrations νs(COO-). The separation (Δν) between νas

(COO-) and νs (COO

-) of 170 cm

-1 for the Cd (II) complex suggest monodentate

coordinating modes for the coordinated carboxylate group (Cao et al., 2002). The

absence of characteristic band at 1700 cm-1

for protonated carboxylate groups indicated

that all the carboxylate groups of the ligand were deprotonated, and is also in

accordance with the XRD findings (Cao et al., 2002; Wang et al., 2012a). The

absorption at 1487 cm-1

was combination of benzene ring stretching and deformation

modes while the peak around 633 cm-1

was associated to bending vibration of C–H (Wu

et al., 2014).

4000 3600 3200 2800 2400 2000 1600 1200 800 400

80

82

84

86

88

90

92

94

96

98

100

Tra

nsm

itta

nce

(%

)

Wavenumber (cm-1)

C-H vs(COO-) vas(COO-) O-H

a)

46

4000 3600 3200 2800 2400 2000 1600 1200 800 400

92

94

96

98

100

Tra

nsm

itta

nce

(%

)

Wavenumber (cm-1)

vs(COO-) C-H vas(COO-) O-H

b)

4000 3600 3200 2800 2400 2000 1600 1200 800 400

92

94

96

98

100

Tra

nsm

itta

nce

(%

)

Wavenumber (cm-1)

vs(COO-) C-H vas(COO-) O-H

c)

47

Figure 4.5: FTIR spectrum of (a) pure Cd-MOF, (b) Ag-Cd-MOF, (c) Fe-Cd-MOF

and Zn-Cd-MOF.

The thermal stability of the linkers in the studied samples was established

through Thermogravimetric Analysis (TGA) and is depicted in Figure 4.7. For complex

Cd-MOF, two stages of weight loss were observed; the first step falling within the range

between 100 to 258°C corresponds to the loss of water molecules that bound to the

framework. The later observed between 400oC to 650

oC was attributed to the

decomposition of carbon ligand. The MOF synthesized in the present study exhibited

robust thermal stability compared with reports. In general MOFs reported in the

literatures are decomposed at 350oC (Min et al., 2001). Similar two stages were

observed for Fe3+

and Zn2+

intercalated MOFs. However, Ag+ intercalated had a poor

stability, increasing the temperature beyond 300oC collapsed the scaffold of framework.

The Cd-MOF showed similar thermal stability curve as [Ni(H2O)4(bipy)(BTA)0.5·H2O]

4000 3600 3200 2800 2400 2000 1600 1200 800 400

92

94

96

98

100

Tra

nsm

itta

nce

(%

)

Wavenumber (cm-1)

vs(COO-) C-H vas(COO-) O-H

d)

48

consisting of a distorted octahedral configuration (Gao et al., 2012). This is because the

thermal stability of the synthesized MOFs is influenced by the coordination number and

local coordination environment instead of the framework topology (Mu & Walton,

2011). The resulting residue at the end of the TGA experiment is CdO.

100 200 300 400 500 600

30

40

50

60

70

80

90

100

We

igh

t lo

ss (

%)

Temperature (C)

a)

100 200 300 400 500 600

30

40

50

60

70

80

90

100

We

igh

t lo

ss (

%)

Temperature (C)

b)

49

100 200 300 400 500 600

40

50

60

70

80

90

100

We

igh

t lo

ss (

%)

Temperature (C)

d)

Figure 4.6: Thermogravimetric curve of (a) Cd-MOF, (b) Ag-Cd-MOF, (c) Fe-Cd-

MOF and (d) Zn-Cd-MOF.

100 200 300 400 500 600

40

50

60

70

80

90

100

We

igh

t lo

ss (

%)

Temperature (C)

c)

50

Understanding the optical characteristics of synthesized MOFs is a foremost for the

light driven energy materials and the major aim of the present dissertation is to develop

an alternative visible light responsive photocatalyst through MOF and the obtained

spectrum is illustrated in Figure 4.8a. The H4btec responded with strong absorption in

the ultraviolet light region that can be ascribed to the π*→π transitions in the linker. In

contrast to the H4btec ligand, the ions intercalated MOF shown red-shift as a resultant

ligand coordination to the metal centers (LMCT) (Guo et al., 2012a). After the insertion

of metal ions into the framework of Fe-Cd-MOF displayed an significant

photoresponse in the visible region, while Ag-Cd-MOF and Zn-Cd-MOF resulted in

trivial (Fuerte et al., 2001; Yang et al., 2010).

The optical diffuse-reflection spectra of MOFs were measured using Kubelka–Munk

function (Kan et al., 2012; Leong et al., 2014). As shown in Figure 4.8b, the energy

difference obtained by the extrapolation of the linear portion of the absorption edges

was estimated to be 3.6 eV for Cd-MOF. Meanwhile the energy gaps of Ag+, Zn

2+ and

Fe3+

intercalated Cd-MOF are 3.5 eV, 3.4 eV and 2.0 eV respectively. It is evident that

Fe3+

possessed the narrowest band gaps signifying that insertion of Fe3+

into the

framework of parent complex was a realistic strategy for expanding the spectrum

towards longer wavelength photons and are abundantly available in the solar spectrum

(Wang et al., 2015). The presence of d10

metal atoms in the framework center

contributed for such marvelous behavior (Guo et al., 2012a; Hua et al., 2010; Wang et

al., 2012a).

51

Figure 4.7: (a) Optical property (b) energy gap of the synthesized MOFs.

300 400 500 600 700

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Inte

nsity (

a.u

)

Wavelength (nm)

H4btec

Cd-MOF

Ag-Cd-MOF

Fe-Cd-MOF

Zn-Cd-MOF

a)

1 2 3 4 5

0

1

2

3

4

5

6

7

(F(R

)hv)0

.5

hv(eV)

Cd-MOF

Ag-Cd-MOF

Fe-Cd-MOF

Zn-Cd-MOF

b)

52

Further, the photoluminescence attributes of the MOFs and free organic H4btec

linker was investigated in the solid state at room temperature and portrayed in Figure

4.9. The spectra revealed that H4btec linker displayed weak fluorescent emission with

λmax at 397 up on excitation at 325 nm. In general, the free H4btec linker exhibit weaker

luminescent emission bands at 397 nm, signified to the intra-ligand (π*- n or π*- π)

emission (Wen et al., 2009; Zou et al., 2013). In comparison to the H4btec linker, the

emission maxima of Cd-MOF and ions intercalated MOF were significantly red shifted

with emission peak at 420 nm for Ag-Cd-MOF, as for Cd-MOF and Zn-Cd-MOF its

luminescent were 425 nm and Fe-Cd-MOF showed emission band at 440 nm upon

excitation at 325 nm. Since Cd (II) ions was difficult to oxidize or reduce due to its

stable d10 configurations, the emissions were neither metal-to-ligand charge transfer

(MLCT) nor ligand-to-metal charge transfer (LMCT) in nature. Hence, the observed

shift of the emission band may be caused by deprotonated effect of H4btec and also

should be assigned to coordination interactions of H4btec carboxylate groups to Cd (II)

atoms (Xia et al., 2016).

53

300 400 500 600 700

Inte

nsity (

a.u

)

Wavelength (nm)

H4btec

Cd-MOF

a)

300 400 500 600 700

Inte

nsity (

a.u

)

Wavelength (nm)

Ag-Cd-MOFb)

54

Figure 4.8: Photoluminescence spectra of free H4btec linker, Cd-MOF, and intercalated

Cd-MOF at room temperature (λex= 325nm).

300 400 500 600 700

Inte

nsity (

a.u

)

Wavelength (nm)

Fe-Cd-MOFc)

300 400 500 600 700

Inte

nsity (

a.u

)

Wavelength (nm)

Zn-Cd-MOFd)

55

XPS analysis was carried out to explore the surface elemental composition of

prepared MOFs. Figure 4.10 is full spectrum of Cd-MOF showed the presence of

elements in the as-synthesized materials. The C 1s spectrum in Cd-MOF displayed three

distinct peaks located at 284.86, 286.26 and 288.37 eV. These peaks corresponding to

C–C, C–O, C=O and O–C=O groups respectively (Peng et al., 2011; Wang et al., 2014).

From Figure 4.10d, the binding energy of O1s core level was observed at 531.8 eV

resembles to the characteristics of O2-

ions in the crystalline network and a shoulder

located at the side of higher binding energies, indicating the presence of abundant

surface hydroxyl groups or chemisorbed water molecules. These findings were in good

agreement with the literature reports (Hall et al., 2013). In the 3d core level

photoelectron for Cd in pure Cd-MOF, the peaks observed at 405.01 and 411.95 eV

were related to Cd5/2 and Cd3/2 electrons respectively. The intercalation of metal ions

into framework of Cd-MOF shifted Cd peak towards higher energies. These can be

ascribed to the formation of new Mn+

– O (Mn+

= Ag2+

, Fe3+

and Zn2+

) (Wang et al.,

2006). Figure 4.11, the peaks Cd5/2 and Cd3/2 for Ag-MOF, Fe-MOF and Zn-MOF

appeared at 405.09, 412.5 eV: 405.24, 412.18 eV: 405.07, 411.98 eV respectively.

Furthermore, Figure 4.12 displayed the clear presence of intercalated metal species in

framework. The peaks at 367.81, 373.91 eV: 711.34, 724.54 eV: 1022.15, 1045.15 eV

corresponding to Ag 3d5/2, Ag 3d3/2: Fe 2p3/2, Fe 2p1/2: Zn 2p3/2, Zn 2p1/2 respectively.

The binding energies of inserted metal ions in framework shifted to higher energy level

than that of pure Cd-MOF. These inference clearly substantiated the intercalation of

metal ions into the framework (Zhu et al., 2006).

56

0 300 600 900 1200Binding Energy (eV)

Binding energy (eV)

Inte

ns

ity

(a.u

)

C 1s

Cd 3d5/2

Cd 3d3/2

O 1s

(a)

396 400 404 408 412 416 420Binding Energy (eV)

Inte

ns

ity

(a.u

)

Binding energy (eV)

Cd 3d3/2

Cd 3d5/2

(b)

57

Figure 4.9: XPS spectrum of (a) Cd-MOF and Close up survey at (b) Cd, (c) C and

(d) O core level.

280 284 288 292 296Binding Energy (eV)

Binding energy (eV)

Inte

nsit

y (a

.u)

C-C

O-C=O

C-O

(c)

525 528 531 534 537Binding Energy (eV)

O 1s

Binding energy (eV)

Inte

ns

ity

(a.u

)

(d)

58

0 300 600 900 1200Binding Energy (eV)

Inte

nsit

y (a

.u)

Binding energy (eV)

C 1s

Ag 3d

Cd 3d5/2

Cd 3d3/2

O 1s

(a)

0 300 600 900 1200Binding Energy (eV)

C 1s

Cd 3d3/2

Cd 3d5/2

O 1s

Fe 2p

Inte

nsit

y (

a.u

)

Binding energy (eV)

(b)

396 400 404 408 412 416 420Binding Energy (eV)

Cd 3d5/2

Cd 3d3/2

Inte

ns

ity (

a.u

)

Binding energy (eV)

59

Figure 4.10: XPS spectrum of (a) Ag-Cd-MOF, (b) Fe-Cd-MOF and (d) Zn-Cd-

MOF (inset: close up for Cd core level in Ag-CdMOF, Fe-CdMOF and Zn-CdMOF

respectively).

0 300 600 900 1200Binding Energy (eV)

Binding energy (eV)

Inte

ns

ity (

a.u

)

C 1s

Cd 3d5/2

Cd 3d3/2

O 1s

Zn 2p

(c)

360 364 368 372 376 380 384Binding Energy (eV)

Inte

nsi

ty (

a.u

)

Binding energy (eV)

Ag 3d5/2

Ag 3d3/2

(a)

396 400 404 408 412 416 420 424Binding Energy (eV)

Cd 3d5/2

Cd 3d3/2

Inte

ns

ity (

a.u

)

Binding energy (eV)

60

Figure 4.11: XPS spectrum of intercalated metal ions Cd-MOF (a) Ag+ (b) Fe

3+ and

(c) Zn2+

.

700 705 710 715 720 725 730 735 740Binding Energy (eV)

Inte

nsi

ty (

a.u

)

Binding energy (eV)

Fe 2p3/2 Fe 2p1/2

(b)

1010 1015 1020 1025 1030 1035 1040 1045 1050 1055Binding Energy (eV)

Zn 2p3/2

Zn 2p1/2

Inte

ns

ity (

a.u

)

Binding energy (eV)

(c)

61

The effect of catalyst loading on degradation of 2-CP was presented in Figure 4.13a.

Different amount of Cd-MOF dosage varied from 60 to 240 mg was used in 200 ml of

2-CP solution. The optimum loading of Cd-MOF was found at 180 mg where 54 %

degradation of 2-CP was achieved but further increase in the catalyst dosage until 240

mg slightly decreased the 2-CP degradation efficiency to 49 %. This is due to increased

opacity of the solution which impedes the light transmission through the solution. As

the light intensity decreased, the photo generation of electrons and positive holes would

be reduced thus the phodegradation efficiency also reduced (Abbad et al., 2013; Ghorai,

2011; Mangrulkar et al., 2011).

pH is one of the critical parameters that influences photodegradation in

presence of Cd-MOF (Doong et al., 2001; Theurich et al., 1996). Considering its

importance the study was carried out and the obtained relationship is presented in

Figure 4.13b. The experiment clearly showed that only 42% of 2-CP was

degraded in acidic condition. This is because at lower pH the positively charged

surface hinders the reaction between the positive holes with water molecule

results in poor yield of hydroxyl ions and in turn radicals (Ajeel et al., 2015;

Barakat et al., 2005). However the efficiency increased with increase in pH,

reaching a maximum of 93 % at pH 9. The alkaline conditions favors the

oxidation reaction and yield higher concentration of (OH-) to react with holes to

form highly reactive short lived (*OH), thus easily oxidized the 2-CP (Ajeel et

al., 2015; Barakat et al., 2005).

The solar light photocatalytic efficacy of the synthesized MOFs were studied by

adopting of 2-CP as the model and is illustrated in Figure 4.13c. The Cd-MOF resulted

in ~69 % removal of 2-CP within 5 h of exposure of day light. Notably, metal ions

intercalated Cd-MOF showed significant enhancement in the removal of 2-CP. When

irradiated with solar light, MOF intercalated with Fe3+

displayed higher removal

62

efficiency i.e., 92 % in 5 h while 75 % and 80 % was observed for Ag+

and Zn2+

respectively. The obtained enhanced photocatalytic activity of Fe was attributed by

several factors: firstly, energy gap of both phototocatalysts were lower than the rest,

enabling the easy charge transfer in Fe-Cd-MOF. Second, Fe-Cd-MOF were

significantly exhibited red shifted optical property while rest trivial. The aforesaid two

significant qualities contributed by the intercalated ions triggered the visible light

photocatalytic activity of Fe-Cd-MOF photocatalyst (Wen et al., 2012; Xu et al.,

2014b). On the other said, the structural factors including coordinated water molecule,

organic ligands and varied central metal significantly influenced photocatalytic activity

of the Fe3+

intercalated Cd-MOF (Chen et al., 2012; Kan et al., 2012).

Table 4.3: Percentage degradation of 2-CP with synthesized MOFs under solar light

irradiation.

Catalyst Time (hours) Condition Percentage of

Degradation (%)

P25 5 Solar light 29

Cd-MOF 5 Solar light 69

Ag-Cd-MOF 5 Solar light 75

Fe-Cd-MOF 5 Solar light 92

Zn-Cd-MOF 5 Solar light 80

63

0 1 2 3 4 5

0.0

0.2

0.4

0.6

0.8

1.0

C/C

o

Time (hours)

60mg

120mg

180mg

210mg

a)

0 1 2 3 4 5

0.0

0.2

0.4

0.6

0.8

1.0

C/C

o

Time (hours)

pH 4

pH 7

pH 9

pH 10

b)

64

Figure 4.12: (a) Effect of catalyst loading, (b) effect of pH on degradation of 2-CP for

Cd-MOF and (c) Solar light photocatalysis pure and metal ions intercalated Cd-MOF on

degrading aqueous solution 2-CP.

The reuse of the MOF photocatalyst was examined since reusing over few cycles

would reduce the cost of the treatment. The recycle results are displayed in Figure 4.14

only Cd-MOF, Fe-Cd-MOF was considered by this case and were reused. The results

showed no major changes in the degradation profile as compared with the virgin cycle.

Further the recovered MOFs were subjected to powder XRD analysis and the results

were compared with virgin sample (Figure 4.15). Peaks of virgin and used were similar,

indicating that their structures were stable and not ruptured in the day light

photocatalysis. The study demonstrated the structural stability of the synthesized MOF

because the structure plays a key role in delivering the photocatalysis functionality.

0 1 2 3 4 5

0.0

0.2

0.4

0.6

0.8

1.0

C/C

o

Time (hours)

without catalyst

P25

Cd-MOF

Ag-Cd-MOF

Fe-Cd-MOF

Zn-Cd-MOF

c)

65

Figure 4.13: Reusability study of (a) Cd-MOF and (b) Fe-Cd-MOF in degrading

aqueous 2-CP.

1 2 3

0.0

0.2

0.4

0.6

0.8

1.0

C/C

o

Photocatalytic runs

a)

1 2 3

0.0

0.2

0.4

0.6

0.8

1.0

C/C

o

Photocatalytic runs

b)

66

Figure 4.14: Structural comparison of the virgin and used (a) Cd-MOF and (b) Fe-Cd-

MOF.

10 20 30 40 50

Inte

nsity (

a.u

)

2

Cd-MOF (after application)

Cd-MOF (before application)a)

10 20 30 40 50

Inte

nsity (

a.u

)

2

Fe-Cd-MOF (after application)

Fe-Cd-MOF (before application)b)

67

A simple photodegradation kinetics of the 2-CP degradation by Cd and ions

intercalated MOFs were further analyzed. The 2-CP photodegradation followed the first

order kinetics model (Wen et al., 2012). It can be seen from Figure 4.16, rate constant

for 2-CP degradation in the presence of Fe-Cd-MOF is 0.0325 min-1 a

nd Cd-MOF is

0.0189 min-1

respectively. Meanwhile, for Ag+ and Zn

2+ intercalation resulted in 0.0209

min-1

and 0.0258 min-1

. The dominant rate constant for Fe3+

intercalation advocated its

lower energy gap that empowered the easy charge transfer from Highest Occupied

Molecular Orbital (HOMO) to Lowest Unoccupied Molecular Orbital (LUMO) on

photoexcitation (Wen et al., 2012).

Figure 4.15: The fitted reaction kinetics of 2-CP degradation triggered by solar light.

The movement of electrons for Cd-MOF and metal ions intercalated Cd-MOF is

discussed based on HOMO-LUMO principle with the support of obtained results from

various characterization tools. A graphical that metaphorize the functionality of the

MOFs under the illumination of the day light is portrayed clearly in Figure 4.17. During

the photocatalysis HOMO was mainly contributed by oxygen and (or) nitrogen 2p

0 1 2 3 4 5

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

P25

Cd-MOF

Ag-Cd-MOF

Fe-Cd-MOF

Zn-Cd-MOF

ln(C

/Co)

Time (hours)

68

bonding orbitals and LUMO by empty transition metal orbitals. Under the day light

irradiation, electrons (e-) in the HOMO of Cd-MOF were excited to its empty orbital of

LUMO, while leaving the holes (h+) in the HOMO orbitals. The HOMO strongly

demands one electron to return to its stable state. Therefore, an electron was captured

from water molecules, which was oxygenated into *OH active species. Meanwhile, the

electrons (e-) in LUMO could be combined with the oxygen adsorbed on the surfaces of

Cd-MOF to form *O

2−. It then further generates a strong reactive oxygen species,

*OH

most responsible for the degradation of 2-CP along with *O

2− (Guo et al., 2012b; Lin et

al., 2013; Wen et al., 2009). After inserting Fe3+

into the Cd framework, new energy

level status obtained between the LUMO of pure Cd-MOF and the 3d orbital of Fe-Cd-

MOF that can be considered as LUMO of Fe-Cd-MOF (Figure 4.17b). The energy gap

of intercalated Cd-MOF was significantly because of LUMO energy level of Fe-Cd-

MOF is lower than pure Cd-MOF and its HOMO energy level is retained with pure Cd-

MOF. So, the electrons in Fe-Cd-MOF are expected to excite from HOMO to the newly

formed LUMO orbitals with lower energy gap than the pure Cd-MOF. Moreover the

visible light utilisation of Fe-Cd-MOF can be attributed to the match LUMO of Cd-

MOF for the 3d orbital of Fe3+

(Xu et al., 2014b).

69

Figure 4.16: Mechanistic of synthesized MOF on excitation under solar light on degradation of 2-CP (a) pure Cd-MOF and (b) Fe- Cd-MOF

LUMO

HOMO

LUMO

HOMO

3d orbital of

Fe (III)

LUMO of

Fe-Cd-MOF

HOMO

(b) (a)

e- e- e-

h+ h+ h+

e- e- e-

h+ h+ h+

e- e- e-

h+ h+ h+

Solar

irradiation

Solar

irradiation e-

2.0 eV

e-

3.6 eV

70

4.2 Cu-MOF: Inherent Physical-Chemistry

The monomeric unit of Cu-MOF is presented in Figure 4.18. This structure

comprises of two copper metals, one H4btec linker and one Bimb linker respectively.

The coordination of Cu in Cu-MOF can be ascribed as square planar arrangements

surrounded by two oxygen atoms from carboxylate groups of btec4-

, one bimb nitrogen

atom and three oxygen atoms from coordinated water (Min et al., 2001). Moreover, all

the btec4-

linkers were deprotonated and adopted bridging and chelating coordination

modes (Cao et al., 2002; Nara et al., 2013).

Figure 4.17: Structure of synthesized Cu (II) MOF structure.

71

Powder XRD pattern of synthesized Cu-MOF was shown in Figure 4.19, the

peaks at 43.3°

and 50.5° proved

the existence of copper in Cu-MOF. These peaks and

their corresponding plane were highly crystalline reflections in accordance to the

standard diffraction peaks of copper (JCPDS, file No. 04-0836) (Zhou et al., 2008). The

average crystallite size of Cu was measured to be 43.92 nm through Scherrer’s equation.

Observations by FESEM discovered that Cu-MOF possesses flat needle-like structures

with good enough surface area with non-uniform distribution of the crystal. The size of

each crystal measured ~50 μm.

Figure 4.18: As synthesized XRD pattern of copper (II) MOF with JCPDS reference

peak.

72

Figure 4.19: Morphology of Cu (II) MOF.

a)

b)

73

The FTIR spectrum is Cu-MOF in shown in Figure 4.21. From the spectrum an

existence of two peaks (1456 cm-1

and 1448 cm-1

) for antisymmetric vas(COO-) and for

symmetric stretching vibrations vs(COO-) at 1356 cm

-1 indicated the carboxylate groups

coordinate to the Cu (II) atom in both bridging and chelated mode (Cao et al., 2002;

Nara et al., 2013). The absorption band at 3037 cm-1

, 3393 cm-1

and 732 cm-1

attributed

to O-H, N-H and NH2 respectively. Presence of characteristic bands 2382 cm-1

, 1634

cm-1

and 1218 cm-1

were assigned to C-H aldehyde stretch, C=C in azine and C-N

stretch respectively. Similar with Cd-MOF the absence of peak around 1700 cm-1

illustrated all carboxylic acid groups in synthesized Cu-MOF was deprotonated (Cao et

al., 2002).

The thermal stability of synthesized MOF was examined between 27 to 700°C

and the obtained weight loss against temperature is illustrated in Figure 4.22. The TG

curve showed three stages of weight loss; first from 150 to 320℃ was due to loss of

water molecules, second in the range of 350–570℃ due to the release of carbon ligands

and the final decomposition took place at 570oC until 700

oC and attributed to the Bimb

linker.

74

Figure 4.20: FTIR of Cu- MOF scuffled with H4btec and Bimb linker.

Figure 4.21: Thermogravimetric profile of Cu-MOF scuffled with dual linkers.

4000 3600 3200 2800 2400 2000 1600 1200 800 400

Tra

nsm

itta

nce

(%

)

Wavelength (cm-1)

N-H O-H C-H C=C C-N NH2

100 200 300 400 500 600 700

60

70

80

90

100

We

igh

t lo

ss (

%)

Temperature (oC)

75

The diffuse reflectance UV-Vis spectra of Cu-MOF as well as linkers were presented

in Figure 4.23. The absorption of H4btec and Bimb linker are attributed to the π*- n or

π*- π transitions of the aromatic rings (Wen et al., 2009; Zou et al., 2013). A clear shift

and robust shift was exhibited by Cu-MOF. The observed shift was as result of the

charge transfer between non-bonding orbital of oxygen and nitrogen atoms to the

unoccupied copper (II) d centers (Wen et al., 2012). The absorption band observed in

the range 550 nm to 600nm was phenomenon of d-d transitions (Komaei et al., 1999;

Thomas et al., 1995). The energy gap of Cu-MOF was measured using Kubelka - Munk

function was estimated to be 1.8 eV.

The photoluminescence of Cu-MOF was analyzed and revealed in Figure 4.24.

H4btec and Bimb linkers were conjugated organic compound which showed strong

fluorescence emission at 396 nm and 590 nm when excited at 325 nm (Xu et al., 2011).

It can be seen that the broad emission peaks for Cu-MOF was shifted with respect to the

free carboxylic acids and Bimb linker. The observed shift of the emission band was

contributed by the ligand to metal charge transfer (LMCT) as reported previously

(Wang et al., 2013a). Besides that, the variation of emission peaks of compound was

likely ascribed to the use of differences linkers and the coordination environment

around central metal ions and moreover the photoluminescence behavior of materials

was associated with the local environments surrounding the metal ion (Bai et al., 2010).

76

Figure 4.22: (a) Optical characteristics of free linkers and Cu-MOF, (b) energy gap

of synthesized Cu-MOF.

300 400 500 600 700

Inte

nsity (

a.u

)

Wavelength (nm)

H4btec

Bimb

Cu-MOF

a)

1 2 3 4 5

10

20

30

40

50

(F(R

)hv)0

.5

hv(eV)

b)

77

Figure 4.23: Photoluminescence spectrum of linkers and Cu-MOF.

The XPS spectrum of Cu-MOF was exposed in Figure 4.25 and it displayed a typical

survey spectrum of CuMOF, showing the presence of Cu, C, O and N. The binding

energy around 284.15, 532.52 and 399.01eV is signified to C, O and N respectively. A

close up survey at Cu core shows presence of peaks at 934.75. Two distinct peaks with

binding energy 934.75 and 955.15 eV was were observed for Cu and assigned to 2p3/2

and 2p1/2 of Cu2+

. This result coincides with satellite peaks in CuO, which designates

that Cu in the MOF is of divalent and is in consistent with XRD analyses (Kumar et

al., 2013; Zhao et al., 2015).

300 400 500 600 700

Inte

nsity (

a.u

)

Wavelength (nm)

Bimb

H4btec

Cu-MOF

78

Figure 4.24: (a) Full XPS spectrum of Cu-MOF, (b) close up survey at Cu core

level.

0 300 600 900 1200Binding Energy (eV)

C 1s

O 1s N 1s

Cu 2p Inte

nsit

y (a

.u)

Binding energy (eV)

(a)

925 930 935 940 945 950 955 960Binding Energy (eV)

Cu 2p3/2

Cu 2p1/2

Inte

nsit

y (

a.u

)

Binding energy (eV)

(b)

79

It is well known that Cu (II) Metal Organic Framework have been reported as an

potential material for photodegradation of organic dyes and phenols (Hou et al., 2014;

Wang et al., 2013b). However its photocatalytic performance on a non-photosensitizing

and recalcitrant compounds like 2-chlorophenol was not studied. Figure 4.26 illustrates

the photodegradation of 2-CP was triggered under solar light. The control experiments

expressed the influence of the solar energy in photolysing it. Nevertheless, its efficiency

was insignificant owing to its poor photolysis ability. A 100 % degradation of 2-CP was

achieved for Cu-MOF in 4 h of illumination of solar light. This achievement is

remarkable for such Cu (II) MOF and was much higher than Cd(btec)0.5(bimb)0.5

reported by Wen and co-workers where they achieved 40.13% of phenol degradation

after 9 h irradiation of simulated solar light(Wen et al., 2012). Selection of different

metal as well as organic linkers and its presence as solo or as bimodal led to different

final structure of compound and heavily influenced the photocatalysis mechanism

(Chen et al., 2012; Kan et al., 2012). The degradation rate followed pseudo first order

degradation kinetics with 0.0683 min-1

.

Moreover, the stability and reproducibility of synthesized Cu-MOF was examined

and shown in Figure 4.27. There is no significant changes in degradation of 2-CP after

Cu-MOF was reused three times. After being used for three times PXRD pattern of Cu-

MOF was similar with original indicating the robust stability of the synthesized MOF.

80

Figure 4.25: (a) Photocatalysis efficiency of Cu-MOF on 2-CP in presence of solar

light (b) Reaction kinetic of degradation pattern exhibited by the Cu-MOF.

0 1 2 3 4 5

0.0

0.2

0.4

0.6

0.8

1.0

C/C

o

Time (hours)

without catalyst

Cu-MOF

a)

0 1 2 3 4

-2.0

-1.5

-1.0

-0.5

0.0

ln(C

/Co)

Time (hours)

R2= 0.0683 min-1

b)

81

Figure 4.26: (a) Reusability of Cu-MOF (b) Structural stability of Cu-MOF before

and after use.

1 2 3

0.0

0.2

0.4

0.6

0.8

1.0

C/C

o

Photocatalytic runs

a)

10 20 30 40 50 60

Inte

nsity(a

.u)

2

Cu-MOF (after application)

Cu-MOF (before application)b)

82

It is clear from the analyses that the central Cu (II) ions and linkers were

involved for the effective photocatalysis. The mechanism involved in the free and

improved movement of electrons and hole under the excitation of solar light is depicted

in Figure 4.28. As like in conventional semiconductor photocatalyst the electron (e-)

from the highest occupied molecular orbital (HOMO) were excited to the lowest

unoccupied molecular orbital (LUMO) while leaving the holes (h+) in the HOMO

orbitals. The electron of the excited state in the LUMO combined with the oxygen

adsorbed on the surfaces of Cu-MOF to form *O

2−, whereas the HOMO demands one

electron to return to its stable state. In order to return to its stable state for HOMO, the

charge transfer excited state mainly contributed from Bimb and aromatic

polycarboxylates linkers was oxygenated water molecules to generate the (*OH)

radicals. Thus generated active reactive oxygen species (ROS) actively involved in

removal of 2-CP (Wang et al., 2013b; Wen et al., 2012)

83

Figure 4.27: Schematic illustration of formation of ROS in the Cu-MOF for active degradation of 2-CP.

e- e- e-

h+ h+ h+

LUMO

HOMO

O2 .O2−

.OH

H2O

CO2 + H2O

2-CP

84

CHAPTER 5: CONCLUSION AND SUGGESTIONS

5.1 Conclusion

In the present study two different metals based metal organic framework namely Cd-

MOF and Cu-MOF successfully synthesized through simple hydrothermal method. An

intercalation of chosen metal ions was adopted for Cd-MOF. Both compounds

displayed diverse structure disclose that selection of metal, multicarboxylic acid and

Bimb linkers play significant role for the formation of synthesized compound.

Cadmium (II) atom coordinated to carboxylate groups in monodentate coordinating

modes forming complex Cd-MOF structure. All synthesized MOF displayed good

thermal stability, photoluminescence and phtotocatalysis. Cd-MOF exhibit lower

photocatalytic activity in contrast to Cu-MOF under solar light irradiation. The

introduction of different metal ions into framework of Cd-MOF decreased energy gap of

HOMO and LUMO. Off all studied Fe3+

showed higher photocatalytic activity than Ag+

and Zn2+

.

Copper (II) atoms in Cu-MOF adopt bridging and chelating mode with carboxylate

group. The usage of dual linkers in Cu-MOF promisingly enhanced the photoresponse

in visible region and embarking photocatalytic efficiency on handling of 2-CP in short

duration. All synthesized compounds have high stability and can be reused at least three

times without loss of its photocatalytic performance. Overall all the synthesized MOFs

had proved its capability and uphold them as a potential replacement for the

conventional semiconductor photocatalyst with superior solar light harvesting

characteristics.

85

5.1 Suggestion

New metal organic framework compounds, Cd-MOF and Cu-MOF were successfully

synthesized by hydrothermal technique present opportunity for this work to be extended

up in the forthcoming.

The synthesis of Cd-MOF and Cu-MOF can be extended using different

techniques like microwave controlled synthesis where it can deliver shape, and

size controlled crystals.

Carbon materials have notable characters including high conductivity hence

modification of MOFs with carbon nano materials should be investigated instead

of metal ions.

The research can be further extended by identifying or developing new

generation linkers, the present linkers are very expensive where by the

production cost of the linker could be brought down.

86

REFERENCES

Abbad, M. M. B., Kadhum, A. A. H., Mohamad, A. B., Takriff, M. S., & Sopian, K.

(2013). Photocatalytic degradation of chlorophenols under direct solar radiation

in the presence of ZnO catalyst. Research on Chemical Intermediates, 39(5),

1981-1996.

Ajeel, M. A., Aroua, M. K., & Daud, W. M. A. W. (2015). Anodic Degradation of 2-

Chlorophenol by Carbon Black Diamond and Activated Carbon Composite

Electrodes. Electrochim. Acta., 180, 22-28.

Allendorf, M., Bauer, C., Bhakta, R., & Houk, R. (2009). Luminescent metal–organic

frameworks. Chemical Society Reviews, 38(5), 1330-1352.

An, J., Geib, S. J., & Rosi, N. L. (2009). Cation-triggered drug release from a porous

zinc− adeninate metal− organic framework. J. Am. Chem. Soc., 131(24), 8376-

8377.

Aslani, A., & Morsali, A. (2009). Sonochemical synthesis of nano-sized metal-organic

lead (II) polymer: A precursor for the preparation of nano-structured lead (II)

iodide and lead (II) oxide. Inorganica Chimica Acta, 362(14), 5012-5016.

Astereki, S., Kamarehie, B., & Jafari, A. (2016). 2-Chlorophenol Removal of Aqueous

Solution Using Advanced Oxidation Processes Resulting from Iron/Persulfate

and Ultra Violet/Persulfate. Iranian Journal of Toxicology, 10(4), 1-8.

Bai, H.-Y., Ma, J.-F., Yang, J., Zhang, L.-P., Ma, J.-C., & Liu, Y.-Y. (2010). Eight two-

dimensional and three-dimensional metal− organic frameworks based on a

flexible tetrakis (imidazole) ligand: synthesis, topological structures, and

photoluminescent properties. Crystal Growth & Design, 10(4), 1946-1959.

Barakat, M., Schaeffer, H., Hayes, G., & Ismat Shah, S. (2005). Photocatalytic

degradation of 2-chlorophenol by Co-doped TiO 2 nanoparticles. Appl. Catal.

B., 57(1), 23-30.

Barthelet, K., Adil, K., Millange, F., Serre, C., Riou, D., & Férey, G. (2003). Synthesis,

structure determination and magnetic behaviour of the first porous hybrid

oxyfluorinated vanado (iii) carboxylate: MIL-71 or V iii 2 (OH) 2 F 2 {O 2 CC

6 H 4-CO 2}· H 2 O. Journal of Materials Chemistry, 13(9), 2208-2212.

Beldon, P. J., Fabian, L., Stein, R. S., Thirumurugan, A., Cheetham, A. K., & Friscic, T.

(2010). Rapid Room‐Temperature Synthesis of Zeolitic Imidazolate Frameworks

by Using Mechanochemistry. Angewandte Chemie International Edition,

49(50), 9640-9643.

Bertran, J. F. (1999). Mechanochemistry: an overview. Pure and Applied Chemistry,

71(4), 581-586.

Bloch, E. D., Britt, D., Lee, C., Doonan, C. J., Uribe-Romo, F. J., Furukawa, H., Long,

J. R., & Yaghi, O. M. (2010). Metal insertion in a microporous metal− organic

87

framework lined with 2, 2′-bipyridine. Journal of the American Chemical

Society, 132(41), 14382-14384.

Boldyrev, V., & Tkacova, K. (2000). Mechanochemistry of solids: past, present, and

prospects. Journal of materials synthesis and processing, 8(3), 121-132.

Braslavsky, S. E. (2007). Glossary of terms used in photochemistry, (IUPAC

Recommendations 2006). Pure and Applied Chemistry, 79(3), 293-465.

Cao, R., Sun, D., Liang, Y., Hong, M., Tatsumi, K., & Shi, Q. (2002). Syntheses and

characterizations of three-dimensional channel-like polymeric lanthanide

complexes constructed by 1, 2, 4, 5-benzenetetracarboxylic acid. Inorg. Chem.,

41(8), 2087-2094.

Cavka, J. H., Jakobsen, S., Olsbye, U., Guillou, N., Lamberti, C., Bordiga, S., &

Lillerud, K. P. (2008). A new zirconium inorganic building brick forming metal

organic frameworks with exceptional stability. Journal of the American

Chemical Society, 130(42), 13850-13851.

Chen, C., Sun, B., Zhao, X., & Zhang, N. (2011). A new 3D metal–organic framework

with (4, 8)-connected AlB 2 topology constructed from coordinated evolution of

a C 3 symmetry ligand. Inorganic Chemistry Communications, 14(9), 1532-

1536.

Chen, Y. Q., Li, G. R., Qu, Y. K., Zhang, Y. H., He, K. H., Gao, Q., & Bu, X. H.

(2013). Water-insoluble heterometal-oxide-based photocatalysts effective for the

photo-decomposition of methyl orange. Crystal Growth & Design, 13(2), 901-

907.

Chen, Y. Q., Liu, S. J., Li, Y. W., Li, G. R., He, K. H., Qu, Y. K., Hu, T. L., & Bu, X.

H. (2012). A two-fold interpenetrated coordination framework with a rare (3, 6)-

connected loh1 topology: Magnetic properties and photocatalytic behavior.

Cryst. Growth Des., 12(11), 5426-5431.

Cho, S. H., Ma, B., Nguyen, S. T., Hupp, J. T., & Albrecht-Schmitt, T. E. (2006). A

metal–organic framework material that functions as an enantioselective catalyst

for olefin epoxidation. Chemical Communications(24), 2563-2565.

Chong, M. N., Jin, B., Chow, C. W., & Saint, C. (2010). Recent developments in

photocatalytic water treatment technology: a review. Water research, 44(10),

2997-3027.

Crespo, P. S., Fernandez, E. V. R., Gascon, J., & Kapteijn, F. (2011). Synthesis and

characterization of an amino functionalized MIL-101 (Al): Separation and

catalytic properties. Chemistry of Materials, 23(10), 2565-2572.

Cui, J., He, T., & Zhang, X. (2013). Synthesis of Fe 3 O 4@ SiO 2@ Pt ion–TiO 2

hybrid composites with high efficient UV–visible light photoactivity. Catalysis

Communications, 40, 66-70.

88

Cui, Y., Xu, H., Yue, Y., Guo, Z., Yu, J., Chen, Z., Gao, J., Yang, Y., Qian, G., & Chen,

B. (2012). A luminescent mixed-lanthanide metal–organic framework

thermometer. Journal of the American Chemical Society, 134(9), 3979-3982.

Dai, M., Li, H. X., & Lang, J. P. (2015). New approaches to the degradation of organic

dyes, and nitro-and chloroaromatics using coordination polymers as

photocatalysts. CrystEngComm, 17(26), 4741-4753.

Das, M. C., Xu, H., Wang, Z., Srinivas, G., Zhou, W., Yue, Y. F., Nesterov, V. N.,

Qian, G., & Chen, B. (2011). A Zn 4 O-containing doubly interpenetrated

porous metal–organic framework for photocatalytic decomposition of methyl

orange. Chemical Communications, 47(42), 11715-11717.

Demazeau, G. (2008). Solvothermal reactions: an original route for the synthesis of

novel materials. Journal of Materials Science, 43(7), 2104-2114.

Dey, C., Kundu, T., Biswal, B. P., Mallick, A., & Banerjee, R. (2014). Crystalline

metal-organic frameworks (MOFs): synthesis, structure and function. Acta

Crystallographica Section B: Structural Science, Crystal Engineering and

Materials, 70(1), 3-10.

Dharmarathna, S., King’ondu, C. K., Pedrick, W., Pahalagedara, L., & Suib, S. L.

(2012). Direct sonochemical synthesis of manganese octahedral molecular sieve

(OMS-2) nanomaterials using cosolvent systems, their characterization, and

catalytic applications. Chemistry of Materials, 24(4), 705-712.

Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A., & Puschmann, H.

(2009). OLEX2: a complete structure solution, refinement and analysis program.

J. Appl. Crystallogr., 42(2), 339-341.

Dong, H., Zeng, G., Tang, L., Fan, C., Zhang, C., He, X., & He, Y. (2015). An

overview on limitations of TiO 2-based particles for photocatalytic degradation

of organic pollutants and the corresponding countermeasures. Water research,

79, 128-146.

Doong, R. A., Chen, C. H., Maithreepala, R., & Chang, S. M. (2001). The influence of

pH and cadmium sulfide on the photocatalytic degradation of 2-chlorophenol in

titanium dioxide suspensions. Water Res., 35(12), 2873-2880.

Du, M., Li, C. P., Liu, C. S., & Fang, S. M. (2013). Design and construction of

coordination polymers with mixed-ligand synthetic strategy. Coordination

Chemistry Reviews, 257(7), 1282-1305.

Dutta, D. P., Ramakrishnan, M., Roy, M., & Kumar, A. (2017). Effect of transition

metal doping on the photocatalytic properties of FeVO4 nanoparticles. Journal

of Photochemistry and Photobiology A: Chemistry, 335, 102-111.

Dybtsev, D. N., Chun, H., Yoon, S. H., Kim, D., & Kim, K. (2004). Microporous

manganese formate: a simple metal− organic porous material with high

framework stability and highly selective gas sorption properties. Journal of the

American Chemical Society, 126(1), 32-33.

89

Ebrahim, A. M. (2013). Doping of Metal Organic Framework (UiO) and for N02

adsorption at ambient Conditions (Master's Dissertation). CUNY Academic

Works.

Eddaoudi, M., Kim, J., Rosi, N., Vodak, D., Wachter, J., O'Keeffe, M., & Yaghi, O. M.

(2002). Systematic design of pore size and functionality in isoreticular MOFs

and their application in methane storage. Science, 295(5554), 469-472.

Feng, D., Gu, Z. Y., Li, J. R., Jiang, H. L., Wei, Z., & Zhou, H. C. (2012). Zirconium‐Metalloporphyrin PCN‐222: Mesoporous Metal–Organic Frameworks with

Ultrahigh Stability as Biomimetic Catalysts. Angewandte Chemie, 124(41),

10453-10456.

Forster, P. M., Thomas, P. M., & Cheetham, A. K. (2002). Biphasic Solvothermal

Synthesis: A New Approach for Hybrid Inorganic− Organic Materials. Chem. of

Mater., 14(1), 17-20.

Foy, A. G. W., Matzger, A. J., & Yaghi, O. M. (2006). Exceptional H2 saturation

uptake in microporous metal-organic frameworks. Journal of the American

Chemical Society, 128(11), 3494-3495.

Friscic, T., & Fabian, L. (2009). Mechanochemical conversion of a metal oxide into

coordination polymers and porous frameworks using liquid-assisted grinding

(LAG). CrystEngComm, 11(5), 743-745.

Friscic, T., Reid, D. G., Halasz, I., Stein, R. S., Dinnebier, R. E., & Duer, M. J. (2010).

Ion‐and Liquid‐Assisted Grinding: Improved Mechanochemical Synthesis of

Metal–Organic Frameworks Reveals Salt Inclusion and Anion Templating.

Angewandte Chemie, 122(4), 724-727.

Frost, H., Düren, T., & Snurr, R. Q. (2006). Effects of surface area, free volume, and

heat of adsorption on hydrogen uptake in metal− organic frameworks. The

Journal of Physical Chemistry B, 110(19), 9565-9570.

Fuerte, A., Alonso, M., Maira, A., Arias, A., Garcia, M., Conesa, J., & Soria, J. (2001).

Visible light-activated nanosized doped-TiO 2 photocatalysts. Chemical

Communications(24), 2718-2719.

Gandara, F., Furukawa, H., Lee, S., & Yaghi, O. M. (2014). High methane storage

capacity in aluminum metal–organic frameworks. Journal of the American

Chemical Society, 136(14), 5271-5274.

Gao, B., Yap, P. S., Lim, T. M., & Lim, T.-T. (2011). Adsorption-photocatalytic

degradation of Acid Red 88 by supported TiO 2: effect of activated carbon

support and aqueous anions. Chemical Engineering Journal, 171(3), 1098-1107.

Gao, L.-L., Liu, Y., Lv, X.-Y., Liu, J.-F., & Hu, T.-P. (2012). Crystal Structure and

Thermal Behavior of Two New Supramolecular Complexes Templated with 1,

2, 4, 5-Benzenetetracarboxylic Acid. International Journal of Inorganic

Chemistry, 2012.

90

Garay, A. L., Pichon, A., & James, S. L. (2007). Solvent-free synthesis of metal

complexes. Chemical Society Reviews, 36(6), 846-855.

Gedanken, A. (2004). Using sonochemistry for the fabrication of nanomaterials.

Ultrasonics sonochemistry, 11(2), 47-55.

Ghorai, T. K. (2011). Photocatalytic degradation of 4-chlorophenol by CuMoO4-doped

TiO2 nanoparticles synthesized by chemical route. Open Journal of Physical

Chemistry, 1(02), 28.

Guillou, N., Livage, C., Drillon, M., & Ferey, G. (2003). The Chirality, Porosity, and

Ferromagnetism of a 3D Nickel Glutarate with Intersecting 20‐Membered Ring

Channels. Angew. Chem. Int. Ed., 42(43), 5314-5317.

Guo, H., Zhu, Y., Qiu, S., Lercher, J. A., & Zhang, H. (2010). Coordination Modulation

Induced Synthesis of Nanoscale Eu1‐xTbx‐Metal‐Organic Frameworks for

Luminescent Thin Films. Advanced Materials, 22(37), 4190-4192.

Guo, J., Ma, J. F., Li, J. J., Yang, J., & Xing, S. X. (2012a). Unusual 2D→ 3D

polycatenane frameworks based on 1D→ 2D interdigitated layers: from single

crystals to submicrometer fibers with enhanced UV photocatalytic degradation

performances. Crystal Growth & Design, 12(12), 6074-6082.

Guo, J., Yang, J., Liu, Y. n., & Ma, J. F. (2012b). Two novel 3D metal–organic

frameworks based on two tetrahedral ligands: syntheses, structures,

photoluminescence and photocatalytic properties. CrystEngComm, 14(20),

6609-6617.

Hall, A. S., Kondo, A., Maeda, K., & Mallouk, T. E. (2013). Microporous brookite-

phase titania made by replication of a metal–organic framework. J. Am. Chem.

Soc., 135(44), 16276-16279.

Han, S. S., & Goddard, W. A. (2007). Lithium-doped metal-organic frameworks for

reversible H2 storage at ambient temperature. Journal of the American Chemical

Society, 129(27), 8422-8423.

He, J., Wang, J., Chen, Y., Zhang, J., Duan, D., Wang, Y., & Yan, Z. (2014). A dye-

sensitized Pt@ UiO-66 (Zr) metal–organic framework for visible-light

photocatalytic hydrogen production. Chemical Communications, 50(53), 7063-

7066.

Henschel, A., Gedrich, K., Kraehnert, R., & Kaskel, S. (2008). Catalytic properties of

MIL-101. Chemical Communications(35), 4192-4194.

Herrmann, J.-M., Duchamp, C., Karkmaz, M., Hoai, B. T., Lachheb, H., Puzenat, E., &

Guillard, C. (2007). Environmental green chemistry as defined by

photocatalysis. Journal of hazardous materials, 146(3), 624-629.

Horike, S., Dinca, M., Tamaki, K., & Long, J. R. (2008). Size-selective Lewis acid

catalysis in a microporous metal-organic framework with exposed Mn2+

coordination sites. Journal of the American Chemical Society, 130(18), 5854-

5855.

91

Hou, Y.-L., Sun, R. W.-Y., Zhou, X.-P., Wang, J.-H., & Li, D. (2014). A copper

(i)/copper (ii)–salen coordination polymer as a bimetallic catalyst for three-

component Strecker reactions and degradation of organic dyes. Chemical

Communications, 50(18), 2295-2297.

Hua, Q., Zhao, Y., Xu, G. C., Chen, M. S., Su, Z., Cai, K., & Sun, W. Y. (2010).

Synthesis, structures, and properties of zinc (II) and cadmium (II) complexes

with 1, 2, 4, 5-tetrakis (imidazol-1-ylmethyl) benzene and multicarboxylate

ligands. Crystal Growth & Design, 10(6), 2553-2562.

Hwang, Y. K., Hong, D. Y., Chang, J. S., Jhung, S. H., Seo, Y. K., Kim, J., Vimont, A.,

Daturi, M., Serre, C., & Férey, G. (2008). Amine grafting on coordinatively

unsaturated metal centers of MOFs: consequences for catalysis and metal

encapsulation. Angewandte Chemie International Edition, 47(22), 4144-4148.

Ishida, T., Nagaoka, M., Akita, T., & Haruta, M. (2008). Deposition of gold clusters on

porous coordination polymers by solid grinding and their catalytic activity in

aerobic oxidation of alcohols. Chemistry–A European Journal, 14(28), 8456-

8460.

Janiak, C. (2003). Engineering coordination polymers towards applications. Dalton

Transactions(14), 2781-2804.

Joaristi, A. M., Alcanniz, J. J., Crespo, P. S., Kapteijn, F., & Gascon, J. (2012).

Electrochemical synthesis of some archetypical Zn2+, Cu2+, and Al3+ metal

organic frameworks. Crystal Growth & Design, 12(7), 3489-3498.

Jung, D. W., Yang, D. A., Kim, J., Kim, J., & Ahn, W.-S. (2010). Facile synthesis of

MOF-177 by a sonochemical method using 1-methyl-2-pyrrolidinone as a

solvent. Dalton Transactions, 39(11), 2883-2887.

Kan, W. Q., Liu, B., Yang, J., Liu, Y. Y., & Ma, J. F. (2012). A series of highly

connected metal–organic frameworks based on triangular ligands and d10

metals: syntheses, structures, photoluminescence, and photocatalysis. Cryst.

Growth Des., 12(5), 2288-2298.

Kim, J., Yang, S.-T., Choi, S. B., Sim, J., Kim, J., & Ahn, W.-S. (2011). Control of

catenation in CuTATB-n metal–organic frameworks by sonochemical synthesis

and its effect on CO 2 adsorption. Journal of Materials Chemistry, 21(9), 3070-

3076.

Kitagawa, S., Kitaura, R., & Noro, S. i. (2004). Functional porous coordination

polymers. Angewandte Chemie International Edition, 43(18), 2334-2375.

Klebanoff, L. (2012). Hydrogen storage technology: materials and applications: CRC

Press.

Klinowski, J., Paz, F. A. A., Silva, P., & Rocha, J. (2011). Microwave-assisted synthesis

of metal–organic frameworks. Dalton Transactions, 40(2), 321-330.

92

Komaei, S. A., Van Albada, G. A., & Reedijk, J. (1999). Synthesis, spectroscopic and

magnetic properties of methoxo-bridged copper (II) complexes with 2-amino-4-

methylpyridine as the ligand. Transition Metal Chemistry, 24(1), 104-107.

Kumar, R. S., Kumar, S. S., & Kulandainathan, M. A. (2013). Efficient electrosynthesis

of highly active Cu 3 (BTC) 2-MOF and its catalytic application to chemical

reduction. Microporous and Mesoporous Materials, 168, 57-64.

Lagashetty, A., Havanoor, V., Basavaraja, S., Balaji, S., & Venkataraman, A. (2007).

Microwave-assisted route for synthesis of nanosized metal oxides. Science and

Technology of Advanced Materials, 8(6), 484-493.

Leong, K. H., Monash, P., Ibrahim, S., & Saravanan, P. (2014). Solar photocatalytic

activity of anatase TiO 2 nanocrystals synthesized by non-hydrolitic sol–gel

method. Solar Energy, 101, 321-332.

Li, D. X., Ren, Z. G., Young, D. J., & Lang, J. P. (2015). Synthesis of two coordination

polymer photocatalysts and significant enhancement of their catalytic

photodegradation activity by doping with Co2+ ions. Eur. J. Inorg. Chem.,

2015(11), 1981-1988.

Lin, H., Liu, P., Zhang, J., Wang, X., & Liu, G. (2013). Two copper (II) metal–organic

networks derived from bis-pyridyl-bis-amide ligands and aromatic

polycarboxylates: a 2-D layered structure and a 4-connected trinodal 3-D

topology. J. Coord. Chem., 66(4), 612-623.

Lin, Z. J., Lu, J., Hong, M., & Cao, R. (2014). Metal–organic frameworks based on

flexible ligands (FL-MOFs): structures and applications. Chemical Society

Reviews, 43(16), 5867-5895.

Liu, J., Chen, L., Cui, H., Zhang, J., Zhang, L., & Su, C.-Y. (2014a). Applications of

metal–organic frameworks in heterogeneous supramolecular catalysis. Chemical

Society Reviews, 43(16), 6011-6061.

Liu, K., Han, X., Zou, Y., Peng, Y., Li, G., Shi, Z., & Feng, S. (2014b). Solvothermal

synthesis, structures, and gas adsorption properties of two cadmium-organic

frameworks. Inorganic Chemistry Communications, 39, 131-134.

Liu, K., You, H., Zheng, Y., Jia, G., Song, Y., Huang, Y., Yang, M., Jia, J., Guo, N., &

Zhang, H. (2010). Facile and rapid fabrication of metal–organic framework

nanobelts and color-tunable photoluminescence properties. Journal of Materials

Chemistry, 20(16), 3272-3279.

Livage, C., Guillou, N., Marrot, J., & Ferey, G. (2001). Construction of two-and three-

dimensional coordination polymers from Cobalt trimesate. Chem. of Mater.,

13(11), 4387-4392.

Long, L.-S. (2010). pH effect on the assembly of metal–organic architectures.

CrystEngComm, 12(5), 1354-1365.

93

Lor, B., Puebla, E., Iglesias, M., Monge, M., Valero, C., & Snejko, N. (2002). In2 (oh)

3 (bdc) 1.5 (bdc= 1, 4-benzendicarboxylate): an In (iii) supramolecular 3d

framework with catalytic activity. Inorganic chemistry, 41(9), 2429-2432.

Lu, W.-G., Deng, J.-H., & Zhong, D.-C. (2012). A novel 3D (4, 5, 14)-connected layer-

pillared metal-organic framework containing rare planar hexnuclear cadmium

(II) clusters. Inorganic Chemistry Communications, 20, 312-316.

Luo, F., & Batten, S. R. (2010). Metal–organic framework (MOF): lanthanide (III)-

doped approach for luminescence modulation and luminescent sensing. Dalton

Transactions, 39(19), 4485-4488.

Mahata, P., Madras, G., & Natarajan, S. (2006). Novel photocatalysts for the

decomposition of organic dyes based on metal-organic framework compounds.

The Journal of Physical Chemistry B, 110(28), 13759-13768.

Malandrino, G., Finocchiaro, S. T., Rossi, P., Dapporto, P., & Fragalà, I. L. (2005).

Multifunctional cadmium single source precursor for the selective deposition of

CdO or CdS by a solution route. Chem. Commun.(45), 5681-5683.

Mangrulkar, P. A., Kamble, S. P., Joshi, M. M., Meshram, J. S., Labhsetwar, N. K., &

Rayalu, S. S. (2011). Photocatalytic degradation of phenolics by N-doped

mesoporous titania under solar radiation. International Journal of Photoenergy,

2012.

Millward, A. R., & Yaghi, O. M. (2005). Metal− organic frameworks with

exceptionally high capacity for storage of carbon dioxide at room temperature.

Journal of the American Chemical Society, 127(51), 17998-17999.

Min, D., Yoon, S. S., Jung, D. Y., Lee, C. Y., Kim, Y., Han, W. S., & Lee, S. W.

(2001). One-dimensional copper–pyridinedicarboxylate polymer containing

square-planar Cu (II) centers exhibiting antiferromagnetic coupling. Inorg.

Chim. Acta., 324(1), 293-299.

Mu, B., & Walton, K. S. (2011). Thermal analysis and heat capacity study of metal–

organic frameworks. The Journal of Physical Chemistry C, 115(46), 22748-

22754.

Nagaveni, K., Hegde, M., & Madras, G. (2004). Structure and Photocatalytic Activity of

Ti1-x M x O2±δ (M= W, V, Ce, Zr, Fe, and Cu) Synthesized by Solution

Combustion Method. J. Phys. Chem. B., 108(52), 20204-20212.

Nara, M., Morii, H., & Tanokura, M. (2013). Coordination to divalent cations by

calcium-binding proteins studied by FTIR spectroscopy. Biochimica et

Biophysica Acta (BBA)-Biomembranes, 1828(10), 2319-2327.

Nguyen, H. G. T., Weston, M. H., Farha, O. K., Hupp, J. T., & Nguyen, S. T. (2012). A

catalytically active vanadyl (catecholate)-decorated metal organic framework via

post-synthesis modifications. CrystEngComm, 14(12), 4115-4118.

Nguyen, T. P., Pham, T. N., Buess-Herman, C., Nguyen, T. T., & Dinh, T. M. T.

(2016). Electrochemical Synthesis of a Metal Organic Framework Material

94

Based on Copper and Benzene–1,3,5–Tricarboxylic Acid Using Applied Current

Malaysian Journal of Chemistry, 18(1), 9-26.

Ni, Z., & Masel, R. I. (2006). Rapid production of metal− organic frameworks via

microwave-assisted solvothermal synthesis. Journal of the American Chemical

Society, 128(38), 12394-12395.

O’Keeffe, M., Peskov, M. A., Ramsden, S. J., & Yaghi, O. M. (2008). The reticular

chemistry structure resource (RCSR) database of, and symbols for, crystal nets.

Accounts of Chemical Research, 41(12), 1782-1789.

Peng, X. Y., Liu, X. X., Diamond, D., & Lau, K. T. (2011). Synthesis of

electrochemically-reduced graphene oxide film with controllable size and

thickness and its use in supercapacitor. Carbon, 49(11), 3488-3496.

Pichon, A., Lazuen-Garay, A., & James, S. L. (2006). Solvent-free synthesis of a

microporous metal–organic framework. CrystEngComm, 8(3), 211-214.

Rao, N., Dubey, A., Mohanty, S., Khare, P., Jain, R., & Kaul, S. (2003). Photocatalytic

degradation of 2-chlorophenol: a study of kinetics, intermediates and

biodegradability. Journal of hazardous materials, 101(3), 301-314.

Reddy, M., & Sivakumar, S. (2013). Lanthanide benzoates: a versatile building block

for the construction of efficient light emitting materials. Dalton Transactions,

42(8), 2663-2678.

Rieter, W. J., Taylor, K. M., & Lin, W. (2007). Surface modification and

functionalization of nanoscale metal-organic frameworks for controlled release

and luminescence sensing. Journal of the American Chemical Society, 129(32),

9852-9853.

Rosi, N. L., Eckert, J., Eddaoudi, M., Vodak, D. T., Kim, J., O'keeffe, M., & Yaghi, O.

M. (2003). Hydrogen storage in microporous metal-organic frameworks.

Science, 300(5622), 1127-1129.

Rowe, M. D., Thamm, D. H., Kraft, S. L., & Boyes, S. G. (2009). Polymer-modified

gadolinium metal-organic framework nanoparticles used as multifunctional

nanomedicines for the targeted imaging and treatment of cancer.

Biomacromolecules, 10(4), 983-993.

Saha, D., Zacharia, R., Lafi, L., Cossement, D., & Chahine, R. (2011). Synthesis,

characterization and hydrogen adsorption on metal-organic frameworks Al, Cr,

Fe and Ga-BTB. Chemical Engineering Journal, 171(2), 517-525.

Sanselme, M., Greneche, J., Riou Cavellec, M., & Ferey, G. (2002). [Fe 2 (C 10 O 8 H

2)]: An antiferromagnetic 3D iron (ii) carboxylate built from ferromagnetic

edge-sharing octahedral chains (MIL-62). Chemical Communications(18), 2172-

2173.

Seo, Y.-K., Hundal, G., Jang, I. T., Hwang, Y. K., Jun, C.-H., & Chang, J.-S. (2009).

Microwave synthesis of hybrid inorganic–organic materials including porous Cu

95

3 (BTC) 2 from Cu (II)-trimesate mixture. Microporous and Mesoporous

Materials, 119(1), 331-337.

Shannon, M. A., Bohn, P. W., Elimelech, M., Georgiadis, J. G., Marinas, B. J., &

Mayes, A. M. (2008). Science and technology for water purification in the

coming decades. Nature, 452(7185), 301-310.

Sharma, A., & Lee, B. K. (2016). Rapid photo-degradation of 2-chlorophenol under

visible light irradiation using cobalt oxide-loaded TiO 2/reduced graphene oxide

nanocomposite from aqueous media. Journal of environmental management,

165, 1-10.

Sheldrick, G. M. (2008). A short history of SHELX. Acta Crystallogr., Sect. A: Found.

Crystallogr, 64(1), 112-122.

Shen, L., Gray, D., Masel, R. I., & Girolami, G. S. (2012). Synthesis and

characterization of a zinc metal–organic framework with chiral nano-pores.

CrystEngComm, 14(16), 5145-5147.

Shultz, A. M., Farha, O. K., Hupp, J. T., & Nguyen, S. T. (2009). A catalytically active,

permanently microporous MOF with metalloporphyrin struts. Journal of the

American Chemical Society, 131(12), 4204-4205.

Silva, C. G., Corma, A., & Garcia, H. (2010). Metal–organic frameworks as

semiconductors. Journal of Materials Chemistry, 20(16), 3141-3156.

Sin, J. C., Lam, S. M., Mohamed, A. R., & Lee, K. T. (2011). Degrading Endocrine

Disrupting Chemicals from Wastewater by TiO. International Journal of

Photoenergy, 2012.

Son, W. J., Kim, J., Kim, J., & Ahn, W. S. (2008). Sonochemical synthesis of MOF-5.

Chemical Communications(47), 6336-6338.

Song, P., Liu, B., Li, Y., Yang, J., Wang, Z., & Li, X. (2012). Two pillared-layer metal–

organic frameworks constructed with Co (ii), 1, 2, 4, 5-benzenetetracarboxylate,

and 4, 4′-bipyridine: syntheses, crystal structures, and gas adsorption properties.

CrystEngComm, 14(6), 2296-2301.

Stock, N., & Biswas, S. (2011). Synthesis of metal-organic frameworks (MOFs): routes

to various MOF topologies, morphologies, and composites. Chemical reviews,

112(2), 933-969.

Sumida, K., Rogow, D. L., Mason, J. A., McDonald, T. M., Bloch, E. D., Herm, Z. R.,

Bae, T.-H., & Long, J. R. (2011). Carbon dioxide capture in metal–organic

frameworks. Chemical reviews, 112(2), 724-781.

Surble, S., Millange, F., Serre, C., Duren, T., Latroche, M., Bourrelly, S., Llewellyn, P.

L., & Férey, G. (2006). Synthesis of MIL-102, a chromium carboxylate metal−

organic framework, with gas sorption analysis. Journal of the American

Chemical Society, 128(46), 14889-14896.

96

Surib, N. A., Sim, L. C., Leong, K. H., Kuila, A., Saravanan, P., Lo, K. M., Ibrahim, S.,

Bahnemann, D., & Jang, M. (2017). Ag+, Fe 3+ and Zn 2+-intercalated

cadmium (ii)-metal–organic frameworks for enhanced daylight photocatalysis.

RSC Advances, 7(81), 51272-51280.

Theurich, J., Lindner, M., & Bahnemann, D. (1996). Photocatalytic degradation of 4-

chlorophenol in aerated aqueous titanium dioxide suspensions: a kinetic and

mechanistic study. Langmuir, 12(26), 6368-6376.

Thomas, K. J., Tharmaraj, P., Chandrasekhar, V., Scott, S. R., & Cordes, A. W. (1995).

Five-coordinate copper (II) complexes of GEM-N 3 P 3 Ph 2 (dmpz) 4.

Polyhedron, 14(8), 977-982.

Titus, M. P., Molina, V. G., Banos, M. A., Gimenez, J., & Esplugas, S. (2004).

Degradation of chlorophenols by means of advanced oxidation processes: a

general review. Applied Catalysis B: Environmental, 47(4), 219-256.

Wang, C.-C., & Ying, J. Y. (1999). Sol-gel synthesis and hydrothermal processing of

anatase and rutile titania nanocrystals. Chemistry of Materials, 11(11), 3113-

3120.

Wang, C., Luo, H., Zhang, Z., Wu, Y., Zhang, J., & Chen, S. (2014). Removal of As

(III) and As (V) from aqueous solutions using nanoscale zero valent iron-

reduced graphite oxide modified composites. J. Hazard. Mater., 268, 124-131.

Wang, D., Ye, J., Kako, T., & Kimura, T. (2006). Photophysical and photocatalytic

properties of SrTiO3 doped with Cr cations on different sites. J. Phys. Chem. B.,

110(32), 15824-15830.

Wang, D. E., Deng, K. J., Lv, K. L., Wang, C. G., Wen, L. L., & Li, D. F. (2009).

Structures, photoluminescence and photocatalytic properties of three new metal–

organic frameworks based on non-rigid long bridges. Cryst. Eng. Comm., 11(7),

1442-1450.

Wang, F., Li, F. L., Xu, M. M., Yu, H., Zhang, J. G., Xia, H. T., & Lang, J. P. (2015).

Facile synthesis of a Ag (I)-doped coordination polymer with enhanced catalytic

performance in the photodegradation of azo dyes in water. J. Mater. Chem. A.,

3(11), 5908-5916.

Wang, X., Liu, Y., Xu, C., Guo, Q., Hou, H., & Fan, Y. (2012a). Series of Cd (II)

metal–organic frameworks based on a flexible tripodal ligand and

polycarboxylate acids: syntheses, structures, and photoluminescent properties.

Crystal Growth & Design, 12(5), 2435-2444.

Wang, X., Luan, J., Lin, H., Lu, Q., Xu, C., & Liu, G. (2013a). Effect of flexible bis-

pyridyl-bis-amide ligands and dicarboxylates on the assembly and properties of

multifunctional Cu (II) metal–organic coordination polymers. Dalton

Transactions, 42(23), 8375-8386.

Wang, X., Luan, J., Lin, H., Xu, C., Liu, G., Zhang, J., & Tian, A. (2013b). The design

and construction of a series of metal–organic coordination polymers based on

97

two isomeric semi-rigid bis-pyridyl-bis-amide ligands and three aromatic

polycarboxylates. CrystEngComm, 15(46), 9995-10006.

Wang, X. S., Chrzanowski, M., Kim, C., Gao, W. Y., Wojtas, L., Chen, Y. S., Zhang,

X. P., & Ma, S. (2012b). Quest for highly porous metal–metalloporphyrin

framework based upon a custom-designed octatopic porphyrin ligand. Chemical

Communications, 48(57), 7173-7175.

Wang, Y., Fang, M., Li, Y., Liang, J., Shi, W., Chen, J., & Cheng, P. (2010). A porous

3d-4f heterometallic metal–organic framework for hydrogen storage.

international journal of hydrogen energy, 35(15), 8166-8170.

Wang, Z., & Cohen, S. M. (2009). Postsynthetic modification of metal–organic

frameworks. Chemical Society Reviews, 38(5), 1315-1329.

Wen, L., Zhao, J., Lv, K., Wu, Y., Deng, K., Leng, X., & Li, D. (2012). Visible-light-

driven photocatalysts of metal–organic frameworks derived from multi-

carboxylic acid and imidazole-based spacer. Crystal Growth & Design, 12(3),

1603-1612.

Wen, L. L., Wang, F., Feng, J., Lv, K. L., Wang, C. G., & Li, D. F. (2009). Structures,

photoluminescence, and photocatalytic properties of six new metal− organic

frameworks based on aromatic polycarboxylate acids and rigid imidazole-based

synthons. Crystal Growth and Design, 9(8), 3581-3589.

Wu, Y., Luo, H., & Wang, H. (2014). Synthesis of iron (III)-based metal–organic

framework/graphene oxide composites with increased photocatalytic

performance for dye degradation. RSC Advances, 4(76), 40435-40438.

Wu, Y. P., Li, D. S., Duan, Y. P., Bai, L., & Zhao, J. (2013). Two new Cu (II)

complexes constructed by mixed-organic tectonics: Structures, magnetic

properties and photocatalytic degradation of organic dyes. Inorganic Chemistry

Communications, 36, 137-140.

Xamena, L. i. F. X., Corma, A., & Garcia, H. (2007). Applications for metal− organic

frameworks (MOFs) as quantum dot semiconductors. The Journal of Physical

Chemistry C, 111(1), 80-85.

Xia, C. K., Wu, F., Yang, K., Sun, W., Min, Y. Y., Wu, Y. L., & Lu, X. J. (2016). Zn

(II) and Cd (II) complexes assembled from versatile 1, 2, 3, 5-

benzenetetracarboxylic acid and chelating N-donor auxiliary coligands.

Polyhedron, 117, 637-643.

Xie, M.-H., Yang, X.-L., & Wu, C.-D. (2011). A metalloporphyrin functionalized

metal–organic framework for selective oxidization of styrene. Chemical

Communications, 47(19), 5521-5523.

Xu, J., Yao, X. Q., Huang, L. F., Li, Y. Z., & Zheng, H. G. (2011). Syntheses,

structures, photoluminescence and magnetic properties of four new metal–

organic frameworks based on imidazole ligands and aromatic polycarboxylate

acids. CrystEngComm, 13(3), 857-865.

98

Xu, W. T., Ma, L., Ke, F., Peng, F. M., Xu, G. S., Shen, Y. H., Zhu, J. F., Qiu, L. G., &

Yuan, Y. P. (2014a). Metal–organic frameworks MIL-88A hexagonal microrods

as a new photocatalyst for efficient decolorization of methylene blue dye. Dalton

Transactions, 43(9), 3792-3798.

Xu, X. X., Cui, Z. P., Gao, X., & Liu, X. X. (2014b). Photocatalytic activity of

transition-metal-ion-doped coordination polymer (CP): photoresponse region

extension and quantum yields enhancement via doping of transition metal ions

into the framework of CPs. Dalton Transactions, 43(23), 8805-8813.

Yang, M., Huang, X., Yan, S., Li, Z., Yu, T., & Zou, Z. (2010). Improved hydrogen

evolution activities under visible light irradiation over NaTaO 3 codoped with

lanthanum and chromium. Materials Chemistry and Physics, 121(3), 506-510.

Yuan, W., Friscic, T., Apperley, D., & James, S. L. (2010). High reactivity of metal–

organic frameworks under grinding conditions: parallels with organic molecular

materials. Angewandte Chemie, 122(23), 4008-4011.

Zaleska, A. (2008). Doped-TiO2: a review. Recent Patents on Engineering, 2(3), 157-

164.

Zhang, X., Zhou, J., Shi, W., Zhang, Z., & Cheng, P. (2013). Two cadmium (II)

coordination polymers constructed by carboxylate and pyridine mixed ligands:

synthesis, structure and luminescent properties. Cryst. Eng. Comm., 15(45),

9738-9744.

Zhao, D., Cui, Y., Yang, Y., & Qian, G. (2016). Sensing-functional luminescent metal–

organic frameworks. CrystEngComm, 18(21), 3746-3759.

Zhao, X., Liu, S., Tang, Z., Niu, H., Cai, Y., Meng, W., Wu, F., & Giesy, J. P. (2015).

Synthesis of magnetic metal-organic framework (MOF) for efficient removal of

organic dyes from water. Scientific reports, 5.

Zhong, D. C., Meng, M., Deng, J. H., Luo, X. Z., & Xie, Y. R. (2011). Synthesis,

crystal structure, and luminescent property of a three-dimensional (3day)

microporous Cd (II) metal-organic framework (MOF) based on mixed ligands.

Inorganic Chemistry Communications, 14(12), 1952-1956.

Zhou, T., Du, Y., Borgna, A., Hong, J., Wang, Y., Han, J., Zhang, W., & Xu, R. (2013).

Post-synthesis modification of a metal–organic framework to construct a

bifunctional photocatalyst for hydrogen production. Energy Environ. Sci., 6(11),

3229-3234.

Zhu, J., Deng, Z., Chen, F., Zhang, J., Chen, H., Anpo, M., Huang, J., & Zhang, L.

(2006). Hydrothermal doping method for preparation of Cr 3+-TiO 2

photocatalysts with concentration gradient distribution of Cr 3+. Appl. Catal. B.,

62(3), 329-335.

Zhu, Q. L., & Xu, Q. (2014). Metal–organic framework composites. Chemical Society

Reviews, 43(16), 5468-5512.

99

Zou, J. Y., Gao, H. L., Shi, W., Cui, J. Z., & Cheng, P. (2013). Auxiliary ligand-assisted

structural diversities of three metal–organic frameworks with potassium 1 H-1,

2, 3-triazole-4, 5-dicarboxylic acid: syntheses, crystal structures and

luminescence properties. Cryst. Eng. Comm., 15(14), 2682-2687.

100

LIST OF PUBLICATIONS AND PAPERS PRESENTED

List of Paper Publication

1. N. A. Surib, L. C. Sim, K. H. Leong, A. Kuila, P. Saravanan, K. M. Lo, S. Ibrahim,

D. Bahneman, M. Jang, (2017). Ag+, Fe

3+ and Zn

2+ Intercalated Cadmium (II)-

Metal-Organic Frameworks for enhanced Day Light Photocatalysis. RSC

Advances, 7, 51272-51280.

2. N. A. Surib, A. Kuila, L. C. Sim, K. H. Leong, P. Saravanan, S. Ibrahim, S. (2018).

A ligand Strategic Approach with Cu- MOF for Enhanced Solar Light

Photocatalysis. New Journal of Chemistry, Under Review.

3. A. Kuila, N. A. Surib, N. S. Mishra, A. Nawaz, K. H. Leong, L. C. Sim, P.

Saravanan & S. Ibrahim (2017). Metal Organic Frameworks: A New Generation

Coordination Polymers for Visible Light Photocatalysis. ChemistrySelect, 2(21),

6163-6177.

4. L. C. Sim, W. H. Tan, K. H. Leong, M. J. Bashir, P. Saravanan & N. A. Surib

(2017). Mechanistic Characteristics of Surface Modified Organic Semiconductor g-

C3N4 Nanotubes Alloyed with Titania. Materials, 10(1), 28.

List of Conference

1. N.A. Surib, L.C. Sim, K.M. Lo, P. Monash, S. Ibrahim, P. Saravanan.

Hydrothermal Synthesis, Structure and Photocatalytic Activities of Cd (II) Metal

Organic Framework Constructed from H4btec. 5

th International Conference on

Functional Materials & Devices (ICFMD 2015). 4-6 August 2015, Johor Bahru,

Malaysia.

101

APPENDIX

Appendix 1

Table 1.0: Peak area value for photodegradation of 2-CP from UPLC performance.

Time (hours)

Peak area from UPLC

Cd-MOF Fe-Cd-

MOF Ag-Cd-

MOF Zn-Cd-

MOF Cu-MOF

Dark Reaction

-1

-0.5

0

487646

485278

483302

364222

359901

350643

447646

445278

440302

209813

207859

204670

4555155

4552564

4471051

Sunlight

0.5 450340 292584 408364 182071 4132188

1 410000 245799 368008 161298 3400002

1.5 370000 195799 327558 143052 2600000

2 340800 137290 296286 120186 1850000

2.5 310065 101888 264965 103806 1350000

3 280391 74349 239391 88793 980000

3.5 250827 49842 207827 72806 670000

4 228514 30519 188714 55080 470006

4.5 198874 12057 164814 44507 290003

5 176084 627 139784 34038 150535