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.