Interfacial synthesis of ZIF-8 membranes with improved nanofiltration performance

Inspired by the traditional RO membrane fabrication method of interfacial polymerization, ZIF-8 membranes were synthesized on porous polyethersulfone supports based on a liquid–liquid interfacial coordination mechanism. ZIF-8 precursors, zinc nitrate and 2-methylimidazole were dissolved in two immiscible solvents, i.e. water and octanol respectively. The support membrane was first saturated with the aqueous zinc nitrate, followed by pouring an octanol based 2-methylimidazole solution on the surface. After a certain reaction time, a selective MOF layer was formed on the porous polymeric support. XRD patterns combined with ATR-IR results and the SEM images of the synthesized membrane confirmed the formation of a continuous ZIF-8 layer, with selectivities in nanofiltration range, indicating the selective role of the ZIF-8 layer. In this work, the influences of synthesis conditions on the ZIF-8 membrane were investigated in detail, including reaction time, precursor concentrations and support effect. The results showed that dense supports, higher mole ratios of 2-methylimizaole to zinc nitrate and higher 2-methylimizaole concentrations led to denser ZIF-8 membranes with less defects.