Synthesis of high-performance Co-based ZIF-67 membrane for H2 separation by using cobalt ions chelated PIM-1 as interface layer

Abstract So far, the reports of ZIF-67 membranes with high permselectivity are rather scarce because ZIF-67 prefers to homogeneous nucleation and growth in the reaction solution rather than heterogeneous nucleation and growth on the substrates. Inspired by the fact that homologous metal ions is helpful to be acted as nucleation centers to promote the preparation of continuous MOF membranes, in this work, we develop a novel and effective synthesis method for in-situ growth of compact ZIF-67 membranes by using Co2+ ions chelated PIM-1 (PIM = polymer of intrinsic microporosity) as interface layer between the ZIF-67 membrane and the α-Al2O3 support. After solvothermal synthesis for 48 h at 120 °C, a well-intergrown ZIF-67 membrane with a thickness of about 12 μm can be formed on the Co2+@cPIM-1 modified α-Al2O3 disk. For single gas permeation at 25 °C and 1 bar, the ZIF-67 membrane shows a high H2 permeance of 6.2 × 10−7 mol m−2 s−1·Pa−1, with H2/CO2, H2/CH4 and H2/C3H8 ideal separation factors of 15.1, 51.7 and 56.4, respectively. Further, other compact and H2 permselective ZIF membranes, such as ZIF-7 and ZIF-8 membranes, can be consistently prepared on the Zn2+@cPIM-1 modified substrates by using the same strategy.