Zeolitic imidazolate frameworks (ZIFs) are a class of metal-organic frameworks that are topologically isomorphic with zeolites. ZIFs are composed of tetrahedrally-coordinated transition metal ions (e.g. Fe, Co, Cu, Zn) connected by organic imidazole linkers. Since the metal-imidazole-metal angle is similar to the 145° Si-O-Si angle in zeolites, ZIFs take on zeolite-like topologies. As of 2010, 105 ZIF topologies have been reported in the literature.
One application of ZIFs is to keep industrial emissions of carbon dioxide out of the atmosphere. One litre of the crystals could store about 83 litres of CO2. The crystals are non-toxic and require little energy to create, making them an attractive possibility for carbon capture and storage. "The porous structures can be heated to high temperatures without decomposing and can be boiled in water or solvents for a week and remain stable, making them suitable for use in hot, energy-producing environments like power plants."
ZIFs are chemically and thermally stable materials. "Study of the gas adsorption and thermal and chemical stability of two prototypical members, ZIF-8 and -11, demonstrated their permanent porosity (Langmuir surface area = 1,810 m2/g), high thermal stability (up to 550°C), and remarkable chemical resistance to boiling alkaline water and organic solvents."
Like zeolites and other porous materials, zeolitic imidazolate framework membranes can be used for the separation of gases because of its highly porous structure, large accessible pore volume with fully exposed edges and faces of the organic links, pore apertures in the range of the kinetic diameter of several gas molecules, and high CO2 absorption capacity. ZIF-8 membranes display high CO2 permeances for equimolar mixtures of CO2 and CH4."
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