Revolutionary MOF-enhanced anion exchange membrane for precise monovalent anion separation through structural optimization and doping

Abstract

Ion selective separations play crucial roles in the fields of energy storage, pollution management, and industrial processes, etc. Ion exchange membranes (IEMs) offer promise for these separations but often lacking the required selectivity. In this work, we have developed a kind of IEM based on metal-organic frameworks (MOFs) to enhance membrane separation performance for electrodialysis (ED). Specifically, for poly(arylene ether sulfone)-based anion exchange membranes (AEMs), we introduced the modified MOFs through doping to create a transport pathway for target ions, leveraging their precise size-based separation effects. This approach significantly improves ion selectivity. Remarkably, at a current density of 2.5 mA·cm−2, the monovalent ion selectivity (Cl−/SO42−) of PAES-UIO-66-Pyr could reach 54.26, while the monovalent ion selectivity (NO3−/SO42−) could reach 55.90. These enhancements may stem from the incorporation of MOF particles, which facilitate the formation of fixed-size channel structures within membrane matrix. These fixed-size channels, coupled with the hydrophobic differences between the original poly(arylene ether sulfone) polymer, created a composite channel system that significantly improved the separation performance for monovalent ions, including Cl−/SO42− and NO3−/SO42−.