Flexible Soft‐Solid Metal–Organic Framework Composite Membranes for H2/CO2 Separation

The development of a facile strategy to construct defect-free and flexible metal-organic framework (MOF)-based membranes with high selectivity and good scalability holds great appeal. Here we report the fabrication of soft-solid MOF composite membranes on polyvinylidene fluoride substrates. A representative membrane comprised of quasi-vertically grown lamellar Zn2 (Bim)4 (Bim=benzimidazolate) and lateral ultrathin polyamide film adhering to the MOF side facets. The straight interlayer galleries within unwrapped Zn2 (Bim)4 acted as predominant pathways, while the polyamide served the function of defect elimination, synergistically inducing an unprecedented H2 /CO2 selectivity of 1084 which set a new record for MOF-based membranes. Separation performance was held constant after membrane rolling up into a tube with a diameter of 3 mm or folding and unfolding at 90° for 50 times. ZIF-67 and ZIF-8 composite membranes based on this strategy also realized extremely high H2 /CO2 separation accuracies. These results, which demonstrate the intrinsic molecular sieving capability of MOFs, will promote the development of MOF-based membranes in practical separation applications.