The effect of different solvents on the formation of large-area MOF membranes

Metal–organic framework (MOF) membranes are widely used in gas separation processes. However, the effect of solvents on the formation of large-area MOF membranes, which directly influences separation performance, has rarely been investigated. In this study, three solvents (methanol, ethanol, and water) were selected to systematically investigate their effects on the zeolite imidazolium frameworks (ZIF) membrane formation via experimental validation and simulations. The results indicated that the solvent selection influenced crystallization rate, crystal size, and ZIF-8 membrane formation ability. Particularly, when water was used as a solvent, slow nucleation and crystallization of the ZIF-8 crystals were observed, resulting in a more complete crystal structure and a thinner ZIF-8 membrane. Therefore, the ZIF-8 membrane exhibited a gas permeance of 10,000 gas permeation unit and enhanced CO₂/N₂ selectivity. Furthermore, ZIF-8 membrane with a surface area of 2400 cm² and spiral-wound membrane modules were developed, paving the way for large-scale industrial production.