Highly oriented mixed-matrix metal-organic framework membranes via spin-coating process for efficient hydrogen separation

Two-dimensional (2D) metal-organic framework (MOF) materials with ultrathin layers, uniform micropores, and extraordinary physicochemical properties exhibit unique mass transport behaviours, enabling them as emerging building blocks for fabricating mixed matrix membranes (MMMs) for hydrogen purification. However, because of the low loading and disordered orientation of 2D MOF materials, high-performance transport paths are often blocked by multisegment polymer matrices, resulting in undesirable hydrogen separation performance. Herein, we report a spin-coating technique for fabricating highly oriented ZIF-7@polybenzimidazole (PBI) MMMs with an ultrahigh 80 wt% of ZIF-7 loading. Through the synergetic manipulation of the spin-coating speed, size, and dispersion of ZIF-7 plates, a high-density distribution of oriented and selective ZIF-7 nanochannels was constructed, enabling the preferential transport of hydrogen molecules. Compared with traditional MMMs with random orientations, the highly oriented ZIF-7@PBI MMM achieved a H 2 permeability of 4505 Barrer and H 2 /CO 2 selectivity of 18.7, surpassing the performance of existing membranes by 8 to 800 times. This study offers great potential for maximising the performance of oriented membranes and provides a viable pathway for developing high-efficiency membranes for various gas separation applications.