The tunable pore structures and ultra-high surface areas of metal-organic frameworks (MOFs) constitute their suitability for gas separation and storage. Zeolitic imidazolate frameworks (ZIFs) are an interesting type of MOFs with tetrahedral units of one bivalent metal M2+ cations (usually Zn2+) and four imidazolate anions (Im-) analogous to {SiO2} tetrahedra in zeolites. As a representative ZIF, Zn(2-methylimidazole)2 (ZIF-8) has a sodalite zeolite-type structure with large pores (11.6 Å in diameter), which are connected by apertures (3.4 Å) large enough for H2 to penetrate into the large pores. However, so far, no research has been reported to explore the effect of water on H2 storage in ZIFs. It is generally recognized that H2O adsorption on a porous material would inhibit H2 adsorption. However, this paper reports that stable H2O-functionalized Zeolitic Zn(2-methylimidazole)2 Framework (ZIF-8), which was obtained by the simple water treatment of ZIF-8 at ambient temperature, can increase its H2 adsorption heat from 5.2 to 10.1 kJ/mol. As a result, the reversible H2 capacity at ambient temperature increased by 77%. This indicates that H2O-functionalization provides a novel approach to enhance ambient-temperature hydrogen storage in ZIF-8 and other metal-organic frameworks (MOFs).

H2O-functionalized zeolitic Zn(2-methylimidazole)2 framework (ZIF-8) for H2 storage

249th National Meeting (2015)

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