Exploring the Versatility of ZIF-8: A Material with Exceptional Stability and Porosity

Porous Zeolitic Imidazolate Frameworks (ZIFs), which belong to the family of Metal-Organic Frameworks (MOFs), are interesting materials because of their use in gas/liquid storage and separation. ZIFs can also be used as heterogeneous catalysts for organic reactions.

Among the varieties of ZIFs, ZIF-8 is an exceptional material due to its structural, chemical and thermal stability. Zeolite-type tetrahedral nets of ZIF-8 are built of tetrahedral atoms of zinc, which are connected by 2-methylimidazole linkers. Compared to other ZIFs, ZIF-8 has larger pores (11.6 Å or 1.16 nm) which are accessible through small apertures of 3.4 Å (0.34 nm), a surface area of 1947 m²/g and a pore volume of 0.663 cm³/g. The product also exhibits excellent thermal stability up to 550 °C.^[1]

There are many potential applications for ZIF-8. Given its high porosity, this material can be used for storage of natural gas (where methane is a major constituent) and alkane separation from CO₂ in the petrochemical industry.^[2-3] In addition, there are reports it as a catalyst (Knoevenagel reaction), or as a catalyst support for metal nanoparticles.^[4]

References:

1. Exceptional chemical and thermal stability of zeolitic imidazolate frameworks Park K S et al. PNAS 2006;103,10186-10191
2. (a) Separation of xylene isomers Micropor. Mesopor. Mat., 2013, 173, 1; (b) Separation of C6 Paraffins Ind. Eng. Chem. Res., 2012, 51, 4692; (c) Effective separation of propylene/propane binary mixtures J. Membrane Sci., 2012, 93, 390.
3. (a) MOF-containing mixed-matrix membranes for CO₂/CH₄ and CO₂/N₂ binary gas mixture separations, Sep. Purif. Technol., 2011, 81, 31. (b) Porous polyethersulfone-supported Zeolitic Imidazolate Framework Membranes for hydrogen separation
4. J. Phys.Chem. C., 2012, 116, 13264.
5. (a) Catalytic activity of ZIF-8 in the synthesis of styrene carbonate, Chem. Commun., 2013, 32, 36.; (b) Iridium nanoparticles stabilized by metal organic frameworks: synthesis, structural properties and catalytic performance Dalton Trans., 2012, 41, 12690; (c) Zeolitic imidazole frameworks: Catalysts in the conversion of carbon dioxide to chloropropene carbonate,

ACS Catalysis, 2012, 2, 180; (d) Expanding applications of metal-organic frameworks: zeolite imidazolate framework ZIF-8 as an efficient heterogeneous catalyst for the Knoevenagel reaction, ACS Catalysis, 2011, 1, 120.