MOF, METAL-ORGANIC FRAMEWORKS:
A VERSATILE CLASS OF ADVANCED
MATERIALS
Presented by
SUMANTA CHAKRABARTY
M.Sc. (Applied Chemistry)
RAMAKRISHNA MISSION
VIDYAMANDIRA
Supervisor:
Dr. Uttam Kumar Ghorai
Assistant Professor,
Ramakrishna Mission Vidyamandira
NANOPOROUS MATERIALS
Consist of a regular organic or inorganic structure, supporting a
periodic porous system
Microporous
Nanoporous
Mesoporous
Materials
Macroporous
ZEOLITES POFs
NANOPOROUS
ZEOLITES :
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 wthin
their 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.
POFs : POROUS ORGANIC FRAMEWORKS
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
Review of Metal-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 tunable
properties and have shown great prospect for various
applications.
Basic structure
Metal ions + Organic units Coordination
(linkers/bridging ligands) polymers
or MOF materials
Structural features
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.
Important of pore size
• 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.
• 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.
Properties of MOFs
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.
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.
for better application:
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.
Synthesis
Hydrothermal/ Solvothermal synthesis
Microwave-assisted synthesis
Ultrasonic Irradiation
Electrochemical synthesis
Chemistry of MOFs
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.
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
SCOPE FOR FUTURE WORK
Super capacitor
application
Pollution control Hydrogen
storage
MOF
Electrochemical
energy storage Catalytic
and conversion activity
ACKNOWLEDGEMENT
Dr. Uttam Kumar Ghorai
Mr. Angsuman Santra
All others members of “VIDYAMANDIRA PARIVAR”
