MOF, METAL-ORGANIC FRAMEWORKS: A VERSATILE CLASS OF ADVANCED

MATERIALS

Supervisor:Dr. Uttam Kumar Ghorai

Assistant Professor,Ramakrishna Mission Vidyamandira

Presented by

SUMANTA CHAKRABARTY

M.Sc. (Applied Chemistry)

RAMAKRISHNA MISSION

VIDYAMANDIRA

Consist of a regular organic or inorganic structure, supporting a periodic porous system

NANOPOROUS MATERIALS

NanoporousMaterials

Microporous

Mesoporous

Macroporous

NANOPOROUS

ZEOLITES POFs

Zeolites are microporous crystalline solids with well-defined structures. Generally they contain silicon, aluminium and oxygen in their framework and cations, water and/or other molecules wthintheir pores.

Zeolites form with many different crystalline structures, which have large open pores (sometimes referred to as cavities) in a very regular arrangement and roughly the same size as small molecules.

The most interesting thing about zeolites is

their open, cage-like, "framework" structure

and the way it can trap other molecules insde

it.

ZEOLITES :

POFs are composed of different organic moieties linked by covalent bonds, resulting in ordered and rigid structure.

Exceptional Thermal stabilities and Low Frameworks Densities.

Exhibit permanent porosity and specific surface areas

Application- Gas storage, Separation, Catalysis

POFs : POROUS ORGANIC FRAMEWORKS

Metal-Organic Framework, abbreviated to MOF, is a Coordination Polymer (or alternatively Coordination Network) with an open framework containing potential voids.

MOFs are self-assembled metal clusters with organic ligands, are well known for their structure, permanent porosity, and tunableproperties and have shown great prospect for various applications.

Review of Metal-Organic Frameworks

Metal ions + Organic units Coordination

(linkers/bridging ligands) polymersor MOF materials

Basic structure

MOFs are structures made up of inorganic nodes, which can either be single ions or

clusters of ions, and organic linkers. They contain potential voids which can be used

for various application.

Very low density.

Crystalline.

Large voids.

Significant van der Waals interaction.

Compelx unit cell.

Structural features

• Many potential applications of MOFs depends on the size and nature of the available free volume or pores within the frameworks structure

• Tuning of the pores is typically achieved by variation of the metal ions or organic ligands

• Lengthening the organic chains can lead to increased pore size but is often limited by a decrease in stability of the framework.

Important of pore size

• With no gas present, the thermal conductivity decreases with increasing pore size. In the presence of adsorbed gas, MOFs with smaller pores experience reduced thermal conductivity due to phonon scattering introduced by gas–crystal interactions.

•For larger pores (>1.7 nm), the adsorbed gas does not significantly affect thermal conductivity.

•This difference is due to the decreased probability of gas–crystal collisions in larger pore structures.

Common ligands used for MOFs

The 2D structures with grid shape are generally synthesized with a molar ratio between the ligand and the metal center of 1:2.

Example: The MOF is constituted by cobalt metal centers and ligands N-(3-pyridyl) nicotinamide .The metal ions are coordinated with four molecules of ligand, which result in a two-dimensional flat-shaped structure.

The backbone of the compound is constructed from metal ions which act as connectors and organic bridging ligands as linkers.

Readily accessible porosity.

The coexistence of inorganic (hydrophilic) and organic (hydrophobic) moieties in structure may influence on adsorption properties.

Although most MOFs are electrical insulators, several materials in this class have recently demonstrated excellent electrical conductivity and high charge mobility.

Properties of MOFs

The thermal stability of MOFs is determined by the coordination number and local coordination environment instead of framework topology.

In general MOFs are poor thermal conductors with a thermal conductivity that is similar to concrete.

Surface Area: MOFs with higher surface area are more desirable.

Pore Size: MOFs must have the proper pore size to allow uptake

and release of analytes.

Stability: MOFs must exhibit reasonable stability upon exposure

to oxygen, moisture, the analytes of interest or changes

in temperature.

Solubility: MOFs should be insoluble in aqueous media.

Analyte Interaction: MOFs may exhibit special structural characteristics that may facilitate selective uptake and release of analytes.

for better application:

Hydrothermal/ Solvothermal synthesis

Microwave-assisted synthesis

Ultrasonic Irradiation

Electrochemical synthesis

Synthesis

The organic linkers used in MOFs are capable of connecting two metal oxide clusters (ditopic linkers).

Linkers with higher dimensionality can also be used.

The bonds formed between the metal ions and the donor atoms of the linker are strong and as a result, the extended network structure in the MOF is quite robust.

The coordination complex formed by the metal ions and the donor atoms of the linker, termed the secondary building unit (SBU), dictates the final topology of the MOF framework

Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications.

Chemistry of MOFs

Active sites on MOFs are located at the metal nodes on the crystalline structure; when the reaction occurs, the framework protects their active sites and increases the efficiency.

Transition metal ions are often used as the inorganic components of MOFs. 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

Organic ligands with rigid backbones are often preferred, because the rigidity makes it easier to predict the network geometry , and in addition the rigidity also helps to sustain the open-pore structure after the removal of the included solvent

Chemistry of MOFs

By using appropriate system it is possible to synthesis extended polymeric or discrete‐closed oligomeric structures. MOFs containing large spaces may result in the formation of interpenetrating structures. Formation of interpenetrating networks can be inhibited by choosing suitable organic ligands.

Chemistry of MOFs

APPLICATIONS

LITERATURE REVIEW

Idea of Hydrothermal synthesis of MOFs

Synthesis of MOFs using M(II) and H3BTC as ligand

Different dimension of synthesised MOFs

Synthesis of interpenetrating MOFs

Structure and Thermal properties of

M(II) MOFs

Yan Qi et.al DOI: 10.1021/cg700758c 2007 American Chemical Society

Hydrothermal synthesis of Ni based MOF

Reaction of 2,3,6,7,10,11-hexaaminotriphenylene with Ni2+ in aqueous NH3 solution under aerobic conditions produces Ni3(HITP)2

(HITP = 2,3,6,7,10,11hexaiminotriphenylene),

Dennis Sheberla et.al American Chemical Society 2014

XRD pattern of

synthesised

Ni3(HITP)2

Conductivity This new 2D MOF The new material

Measurement can be isolated as a highly conductive

black powder or dark blue-violet films.

Synthesis of nanocrystalline Ni(II)-doped MOF-5 via hydrothermal

It was established that the Ni(II)-doped MOF-5 shows superior hydrostability and the sorption profiles of the Ni(II)-doped MOF-5 nanocrystals are dependent on the size of the particles and morphology.

effect of ratio of ethanol and DMF on structure (SEM image)

Ji-Min Yang et al Microporous and Mesoporous Materials Vol 190 ,2014

Application of MOF as gas storage

Identification of policies for designing MOFs with high hydrogen-storage capacities.

The synthesis and structure of a MOF (named MOF-505) based on the NbO topology which has, open metal sites, permanent porosity, two kinds of pores and a high capacity for hydrogen storage.

H2 isotherms for MOF-505 at 77 K after three different activation stape

Banglin Chen et.al 2005 DOI: 10.1002/anie.200462787

MOF

Super capacitor

application

Hydrogen

storage

Catalytic

activity

Pollution control

Electrochemical energy storage and conversion

SCOPE FOR FUTURE WORK

Dr. Uttam Kumar Ghorai

Mr. Angsuman Santra

All others members of “VIDYAMANDIRA PARIVAR”

ACKNOWLEDGEMENT