GO-guided direct growth of highly oriented metal-organic framework nanosheet membranes for H₂/CO₂ 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 = 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.