Ultra-thin size-sieving gas separation membrane by precisely contra-diffusion-match growth of ZIF-67 among GO laminates

Ultrathin and defect-free MOF membranes are actively pursued to realize high-performance hydrogen purification and carbon capture, which are of great significance for energy conservation and environmental sustainability. Zeolitic imidazolate framework-67 (ZIF-67) possesses exceptional pore apertures for sieving hydrogen from other larger gases. However, the preferential heterogeneous nucleation and growth of ZIF-67 crystals greatly challenge the synthesis of ZIF-67 membranes. In this work, a tunable-reaction-zone contra-diffusion synthesis is proposed to effectively assemble ZIF-67 nanocrystals into ultrathin GO laminates. The contradiffusion-match growth of ZIF-67 constructs a compact ZIF-67@GO hybrid structure with superior H2/CO2 separation factor of 140.8 and H2 permeance of 1.7 x 10-7 mol m- 2 s- 1 Pa-1, transcending the state-of-art upper bounds. The excellent separation performance is attributed to the collaborative effect of the size-sieving and the selective attraction of the ZIF-67@GO hybrid structure. Long-term operation also reveals the superior stability of the ZIF-67@GO hybrid membrane for H2/CO2 separation. The rational-design approach grants a novel way to fabricate ultrathin and defect-free ZIF-67 crystalline membranes for high-performance gas separation.