Surface-Engineered Asymmetric Covalent Organic Framework Membranes with Polymers for Improved Ion Transport

Highly oriented two-dimensional (2D) covalent organic frameworks (COFs) possess aligned channels that facilitate efficient ion transport. This structural advantage makes COFs promising membrane materials for reverse electrodialysis (RED) systems. However, to develop ion-exchange membranes suitable for commercialization, it is essential to devise additional strategies that overcome the inherent trade-off between ion conductivity and selectivity. A promising strategy is to create asymmetric properties that enhance ion permeability by suppressing ion collisions while simultaneously improving ion selectivity by restricting reverse co-ion transport. To this end, we introduce polymers onto the COF surfaces to create an asymmetric structure with respect to charge density and hydrophilicity. We demonstrate that even minimal surface modification with polymer chains can induce meaningful asymmetry…