t growth of highly oriented metal – organic framework nanosheet membranes for H 2 / CO 2 separation †

Highly oriented, ultrathin metal–organic framework (MOF) membranes are attractive for practical separation applications, but the scalable preparation of such membranes especially on standard tubular supports remains a huge challenge. Here we report a novel bottom-up strategy for directly growing a highly oriented Zn2(bIm)4 (bIm 1⁄4 benzimidazole) ZIF nanosheet tubular membrane, based on graphene oxide (GO) guided self-conversion of ZnO nanoparticles (NPs). Through our approach, a thin layer of ZnO NPs confined between a substrate and a GO ultrathin layer self-converts into a highly oriented Zn2(bIm)4 nanosheet membrane. The resulting membrane with a thickness of around 200 nm demonstrates excellent H2/CO2 gas separation performance with a H2 performance of 1.4 10 7 mol m 2 s 1 Pa 1 and an ideal separation selectivity of about 106. The method can be easily scaled up and extended to the synthesis of other types of Zn-based MOF nanosheet membranes. Importantly, our strategy is particularly suitable for the large-scale fabrication of tubular MOF membranes that has not been possible through other methods.