Synchronizing Interfacial Reactions at Ionic Liquid/Water Interfaces for Enhanced Organic Solvent Nanofiltration Membranes

Abstract Thin-film nanocomposite (TFN) membranes show great potential for molecular separations, yet their fabrication typically involves multiple steps, including separate nanofiller synthesis, followed by interfacial polymerization. In this work, we report a one-step strategy to fabricate TFN membranes by synchronizing interfacial coordination and polymerization at an ionic liquid/water interface, directly forming an FeTCPP/polyamide hybrid layer on a poly(m-phenyleneisophthalamide) substrate. The membrane prepared with ethanol as a cosolvent in the aqueous phase (denoted TFN-E) was compared with its ethanol-free counterpart (TFN) and a conventional thin-film composite (TFC) membrane in terms of morphology, microstructure, physicochemical properties, and organic solvent nanofiltration (OSN) performance. The effects of nanomaterial loading and ethanol-to-water ratio were investigated. The reaction pathways and the role of ethanol were elucidated. The optimized TFN-E membrane exhibited a permeance 16 times as high as that of the nanomaterial-free TFC membrane (2.4 vs. 0.15 L m–2 h–1 bar–1) while maintaining a high rejection of Congo Red/ethanol. It also demonstrated excellent stability and durability in a variety of organic solvents. This work presents a novel and efficient one-step fabrication route for high-performance TFN membranes for the OSN applications.