ZIF-8 Metal Organic Frameworks (MOFs) Powder for Gas Absorption and Separation, CGASMOFZIF8

ZIF-8 (Zeolitic Imidazolate Framework-8, Zn(MeIM)2, where MeIM = 2-methylimidazolate) is a sodalite-topology metal-organic framework built from tetrahedrally coordinated Zn2+ nodes linked by methylimidazolate rings. The Zn–N–C bond angle (~ 145°) mimics the Si–O–Si bridging angle in classical aluminosilicate zeolites, combining the high chemical/thermal stability of zeolites with the tunable porosity of MOFs.

The key structural features of theZIF-8 are: (1) Sodalite (SOD) Topology: Pore Cavity: Large spherical central cage with a diameter of ~ 11.6 Å. Pore Aperture: Narrow 6-membered ring windows with a nominal crystallographic diameter of ~ 3.4 Å. (2) "Gate-Opening" Framework Flexibility: The 2-methylimidazolate linkers undergo a coordinated rotational "swinging" motion (gate opening) under guest molecule pressure. This increases the effective accessible window diameter from its nominal ~3.4 Å up to ~ 4.0–4.2Å, enabling diffusion of molecules nominally larger than the static aperture. (3) Textural Properties: BET Surface Area: Typically 1300–1800 m2/g; Micropore Volume: 0.60–0.68 cm3/g. Framework Density: ~ 0.95 g/cm3. (4) Robust Chemical Stability: Hydrophobic surface chemistry gives ZIF-8 resistance to boiling water, high-humidity streams, and alkaline environments (pH 9–14), though it degrades in acidic media (pH < 5) due to protonation of the imidazolate linker.

References:

1. W. Chen, et al., Separation of Ethane from Natural Gas Using Porous ZIF-8/Water–Glycol Slurry, Ind. Eng. Chem. Res. (2019) 58 (23): 9997–10006.
2. X. Gong, et al., ZIF-8-Based Membranes for Carbon Dioxide Capture and Separation, ACS Sustainable Chem. Eng. (2017) 5 (12): 11204–11214.