Organosilica-Functionalized Zeolitic Imidazolate Framework ZIF-90 Membrane with High Gas-Separation Performance

Membrane-based separation techniques are energy- and costintensive in comparison with conventional separation processes like distillation and adsorption.[1] Recently, supported metal-organic framework (MOF) films have attracted intense attention for potential applications as semiconductors, sensors, and molecular sieve membranes because of their highly diversified structures and pore sizes as well as specific adsorption affinities.[2–20] In particular, attributed to their zeolite-like properties such as permanent porosity, uniform pore size, exceptional thermal and chemical stabilities, zeolitic imidazolate frameworks (ZIFs) have emerged as a novel type of crystalline porous material for the preparation of superior molecular sieve membranes.[21–23] So far, a series of supported ZIF membranes, including ZIF-7,[24] ZIF-8,[14,25–27] ZIF-22,[28] ZIF-69,[29] and ZIF-90,[30, 31] have been reported for permeation of single gases or separation of mixed gases. Despite much progress in the preparation of MOF membranes, there is still a long road ahead before highly permselective MOF membranes can be developed for practical applications, as highlighted recently.[32] It is often found that the as-prepared MOF layers have a polycrystalline structure containing intercrystalline defects, which are detrimental to the membrane selectivity. Therefore, post-modification of the as-prepared MOF membranes is helpful to minimize the nonselective transport pathways through the intercrystalline gaps.[18, 31