Sandwich‐Like Free‐Standing Covalent Organic Framework Anion Exchange Membranes for Water Electrolysis

Abstract

Abstract Covalent organic frameworks (COFs) offer well‐defined pores for efficient ion transport but suffer from poor mechanical stability. Herein, a sandwich‐like free‐standing COF‐based anion exchange membrane (COF‐AEM) is prepared, combining a COF core with in situ‐grown functional polymer layers. This strategy not only overcomes the polymer/COF incompatibility but also retains the intrinsic nanopores of the COF framework, enabling ion transport with a conductivity of 110 mS cm −1 at 80 °C under a remarkably low ion exchange capacity (IEC) (1.53 mmol g −1 ). Furthermore, the rigid and hydrophobic COF core effectively mitigates the membrane swelling ratio (SR) (5.2% @ 80 °C), while its combination with the flexible hydrophilic polymer skin enhances the robustness of the COF‐AEM simultaneously, achieving a tensile strength of 21.4 MPa. Demonstrated in alkaline water electrolysis, this represents the first free‐standing COF‐AEM for such applications. Our design expands COF‐AEM structural diversity, offering a promising approach for advanced ion‐conductive materials.