Rigid and flexible coupled micropore membranes enabling ultra-efficient anion separation

Abstract

The swift advancement of monovalent anion perm-selective membranes (MAPMs) presents a promising and sustainable approach for anion separation. However, their progress remains predominantly based on microphase-separated membranes characterized by wide, swelling ion-selective channels. In this study, the rigidity and flexibility coupled concept was employed to engineer rigidly confined ion-selective channels within MAPMs to facilitate anion separation. The rigid segments self-assemble into micropores (<0.8 nm), with dimensions precisely modulated by the flexible segments. Under electrodialysis conditions, these membranes demonstrate an order-of-magnitude improvement in selectivity compared with Neosepta® ACS commercial membranes (special for anion separation), with a slight increase in the permeation flux of monovalent anions. The simulation results confirm that the difference in the confinement of various anions, driven by electrostatic interactions within the rigid micropores, is responsible for the exceptional monovalent/bivalent selectivity. Overall, this study provides an alternative strategy to construct rigidly confined channels for efficient anion separation.