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A highly permselective ZIF-100 molecular sieve membrane has been prepared on a polydopamine (PDA)-modified support. Attributed to the formation of strong covalent and non-covalent bonds between PDA and ZIF-100, the ZIF-100 nutrients are attracted and bound to the support surface, thus promoting the growth of well-intergrown and phase-pure ZIF-100 membranes. The developed ZIF-100 membranes show high H2/CO2 selectivity due to the outstanding CO2 adsorption capacity of ZIF-100.

Inspired by the bio-adhesive ability of the marine mussel, highly hydrogen permselective ZIF-8 membranes were prepared on polydopamine functionalized stainless-steel-nets (SSNs). With polydopamine functionalization of SSNs under mild conditions, the nucleation and growth of well-intergrown ZIF-8 membranes were promoted through the formation of strong non-covalent and covalent bonds, which was helpful to enhance the membrane's separation selectivity while maintaining high permeance. For binary mixtures at 100 degrees C and 1 bar, the mixture separation factors of H-2-CO2, H-2-N-2, H-2-CH4 and H-2-C3H8, were found to be 8.1, 15.0, 23.2 and 329.7, which by far exceed the corresponding Knudsen coefficients and those of the as-reported ZIF-8 membranes. The ZIF-8 membranes also displayed high permeances, with the H-2 permeance higher than 2.1 x 10(-5) mol m(-2) s(-1) Pa-1 due to the high void volume of the SSNs.

Making use of the preferred adsorption affinity and capacity to CO 2 as well as the highly porous structure with huge cavities of 2.4 nm, a highly permeable and selective ZIF-95 molecular sieve membrane was developed for the separation of H 2 from CO 2. © 2012 The Royal Society of Chemistry.