Honeycomb ZIF-67 Membrane With Hierarchical Channels for High-Permeance Gas Separation.

Membrane technology exhibits low cost and high efficiency in gas separation. Zeolite-imidazole framework-67 (ZIF-67) membrane shows a theoretically superior performance in H/CO separation, owing to its effective size-sieving pores between H and CO. However, the gas molecules are permeate through a series of consecutive crystal cells of common ZIF-67 polycrystalline membranes, resulting in high transport resistance to the gas permselective transport. To this end, this work employs a contra-diffusion synthesis to construct a honeycomb ZIF-67 (h-ZIF67) crystalline membrane for low-resistance H/CO permselective transport. The controlled growth of h-ZIF67 following the van der Drift theory produces the honeycomb polycrystal with hierarchical channels for low-resistance gas permeation. The prepared membrane with micron-scale thickness still achieves a H permeance as high as 1.6 × 10 mol m s Pa and a H/CO selectivity of 17, which can be maintained after a long-term operation for the H/CO mixture separation.