Skeleton Regulation of Covalent–Organic Frameworks From 2D to 3D Networks for High Anhydrous Proton Conduction

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Developing new materials for anhydrous proton conduction under high‐temperature conditions is very challenging but significant for proton exchange membrane fuel cells. Herein, a series of highly crystalline and robust covalent–organic frameworks (COFs) with different skeletons (2D and 3D) is designed and synthesized using steric hindrance engineering of the monomer. Moreover, a [4 + 2] construction approach is used to construct 3D COFs with entangled networks, which can be further post‐modified with phosphite acid groups to improve intrinsic proton conduction. After loading with imidazole, COFs can realize a proton conductivity of 1.06 × 10 −2 S cm −1 under anhydrous conditions, among the best proton‐conducting COF materials loading imidazole. These materials show high stability at loading and testing conditions and maintain high proton conductivity over a wide temperature range (100–160 °C). This work provides a skeleton regulation approach to design materials for anhydrous proton conduction, showing great potential as high‐temperature proton exchange membranes.