Metal Organic Frameworks (MOFs) for Reversible Gas Storage

Metal Organic Frameworks (MOFs) are porous crystalline compounds in which the vertices (metal ions or clusters of metal ions) are connected to each other by organic molecules called linkers, to form one-, two-, or three-dimensional structures.
The choice of metal and linker has significant effects on the structure and properties of the MOFs, for example, the metal's coordination preference influences the size and shape of pores by dictating the number of ligands that can bind to the metal in different orientation.The objective of this project is the focused improvement of materials for reversible gas storage (hydrogen) and sequestration (carbon dioxide, carbon monoxide) applications especially for on-board applications and clean environment. Designing porous Metal Organic Framework Materials (MOFs) with hydrogen binding energies intermediate between physisorption and chemisorption. Such materials need to reach a binding energy for hydrogen in the range of 15 – 25 kJ/mol averaged over all sorption sites. The key aspects of the project are (a) design and synthesis of porous light weight MOFs with chiral and achiral links and with different metal ions as nodes, (b) induction of porosity in MOF by controlling of interpenetration for high gas uptake capacity, (c) incorporating bio-compatible links (namely alkaloids) for synthesizing bio-MOFs.

Our group has extensively engaged in synthesis and applications of MOFs including gas storage, sequestration, catalysis and proton conduction.

Polyoxometalates (POMs) are accumulation of transition metals (mainly vanadium, molybdenum, tungsten) and oxide clusters with high negative charge. POMs have diverse application in the field of catalysis, electrochemistry, photochemistry, magnetochemistry, and medicine. It is noteworthy that, polyoxometalates have the potential to join metal ions via its peripheral oxygen atoms to form network structures. Research on network structures especially Metal Organic Frameworks (MOFs) has picked up immense attention due to their versatile application in gas storage, sequestration catalysis, drug delivery etc.

Recently researchers attempted to introduce POMs inside the MOFs. POM incorporated MOFs not only introduce functionality inside the structure, but also enhance the thermal stability of the network. Owing to these facts we are interested in design and synthesis of new MOFs composed of transition-metal complexes (TMCs) as well as polyoxometalates (POMs) to produce TMC-linked POMs. This made us interested in the rational synthesis of a series of polyoxometalate-based ionic crystals with [Co(en)₃]³⁺, as this cation had already exhibited absorption, display selective hydrogen (H₂) and carbon dioxide (CO₂) sorption over nitrogen (N₂).

Metal-organic frameworks (MOFs) are porous, crystalline materials in which metal ions are linked together by multidentate, low-molecular-weight (LMW) organic ligands resulting in supramolecular coordination polymers of different topologies. However, the brittle nature of these materials can challenge their industrial processing and combination with other functional materials without pore blocking and/or decrease of the inner surface area. In this sense, it has been suggested that viscoelastic MOF gels (MOFGs) could another new domain of research area, in particular, for high-tech applications in a number of fields such as catalysis, photo physics, sensing, magnetic materials, redox responsiveness, and electron emission. For example, the catalytic potential of wide-ranging metallogel-based materials relies on two major aspects: 1) their two-phase nature, which may facilitate recovering and recycling; and 2) a much higher accessibility of small reagents to the highly solvated 3D porous network in comparison to several standard heterogeneous catalysts.