Limiting the generation of MOF membrane defects via solvent activation to improve separation performance

The MOF membrane has shown great promise for the gases or organic solvent mixtures separation. However, the implementation of MOF membranes remains challenged by defect formation during membrane fabrication. Herein, we reveal that the activation solvent plays a critical role in governing the degree of defect and separation performance in secondary-growth-derived ZIF-8 membranes. The isopropanol activation process exerts excellent membrane structure protection through a synergistic dual mechanism to limit the generation of ZIF-8 membrane defects during drying: (a) The isopropanol inhibits the ZIF-8 seed layer recrystallization and maintains its porous architecture to mitigate interfacial stress during drying through its elastic deformation. (b) The low surface tension of isopropanol minimizes the capillary force during solvent removal to reduce the risk of structural damage. While methanol activation and n-propanol activation have no such structure control. The optimized isopropanol-activated membrane achieves a C₃H₆/C₃H₈ selectivity of 141 to show a 4.8-fold and a 4.4-fold compared to n-propanol- and methanol-activated membranes at room temperature and 1 bar. This study highlights low-surface-tension as an effective strategy for defect suppression in MOF membranes, advancing their potential for industrial hydrocarbon separations.