Achieving Highly Stable and High‐Performance Proton Conductive Covalent Organic Frameworks via Chemical Post‐Modification Strategy

Covalent organic frameworks (COFs) are widely investigated for proton conduction due to their exceptional structural properties, with two primary strategies: designing intrinsically conductive COFs or loading guest molecules (e.g., imidazole). However, the loading strategy is plagued by critical drawbacks, including inconsistent loading quantities and leaching of guest molecules. Additionally, imine-linked COFs often exhibit structural instability in post-synthetic modification (PSM). To address these, we synthesized COF-316 featuring irreversible aromatic ether linkages and modified its nitrile group via PSM to, carboxyl (316-COOH) or amide (316-AM) groups. Modified COFs retained structural integrity, enhanced water vapor adsorption capacity, and improved proton conductivity. Remarkably, 316-AM demonstrated the highest proton conductivity of 2.55 × 10^-2 S cm^-1 (100 °C and 98% RH), among the highest intrinsic conductivities for COFs. Combined activation energy analysis and theoretical calculations clarified proton conduction mechanisms in all three COFs. This study provides valuable insights into functional group engineering for COF-based proton conductors.