Highly efficient H2/CO2 separation via an ultrathin metal-organic framework membrane

We propose a strategy for rapid in situ fabrication of zeolitic imidazolate framework-8 (ZIF-8) hybrid membrane with assistance of the two dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets at room temperature. The negatively charged g-C3N4 nanosheets with abundant nitrogen coordinating sites are capable to capture and anchor Zn2+ and thus provide a large number of heterogeneous nucleation sites for the formation of initial ZIF-8 crystals. During the cyclical spin coating of the Zn2+/g-C3N4 nanosheets and the ligand (2-methylimidazole), the in situ formed ZIF-8 crystal nucleus on g-C3N4 nanosheets promote the further growth of continues defect-free membranes. The ZIF-8/g-C3N4 membrane with thickness of ∼240 nm can be obtained using this strategy within 30 min at room temperature, which is attractive for fast and facile preparation of molecular sieving membranes. Moreover, it exhibits promising H2/CO2 separation performance with the selectivity up to 42, which is superior to many other ZIF-8 membranes.