Optimizing the Through‐Space Conjugation of Vinyl Covalent Organic Frameworks via Bonding Defects Utilization for Enhanced Photocatalysis

ABSTRACT The vinyl covalent organic frameworks (COFs) hold great promise in photocatalytic solar conversion due to the full π ‐delocalization skeleton and porosities. However, the poor reversibility of C═C double bonds formation during their synthesis process leads to unavoidable bonding defects, hindering the photogenerated charge separation and transfer, thereby lowering their photocatalytic activity. In this study, we report the utilization of pre‐existing bonding defects in vinyl COFs through a post‐synthetic modification (PSM) strategy based on their imidization with aromatic amines. By bonding different conjugated aromatic amines, the intralayer and interlayer conjugated structures of vinyl COFs can be effectively enhanced, which facilitate the through‐space conjugation across the framework and optimize the π ‐electronic distribution, thus improving the electronic properties, lowering exciton binding energy ( E b ) and accelerating the charge carrier transfer. Consequently, the aniline‐modified COF with optimized through‐space conjugation exhibits a 5.7‐fold enhancement of photocatalytic absolute hydrogen evolution rate (115.2 µmol h −1 ) with ascorbic acid as a sacrificial agent compared to the original one upon full‐spectrum light irradiation. Besides, the high apparent quantum yields (AQY) of 5.58% at 420 nm and good durability of 28 h upon continuous operation can be observed. To address the bonding defects in vinyl COFs by enhancing the through‐space conjugation, this PSM strategy kills two birds with one stone, paving the way for the structural design of vinyl COFs for advanced application.