Conjugation Lock-In Reinforced Sulfur-Heteropolycyclic Covalent Organic Frameworks with Asymmetric Electron Distribution for Photocatalytic Aerobic Oxidation Reactions
Jiani Yang, Shihuan Gao, Zhenyang Zhao, Xiaohui Xu, Siyuan Liu, Min Xu, Weichao Xue, Fan Dong, Shuang Li, Arne Thomas, Chong Cheng
Abstract
High Resolution Image Download MS PowerPoint Slide The development of robust heterogeneous photocatalysts capable of operating under harsh chemical conditions remains a critical yet challenging goal in materials science. Here, we present a postcyclization strategy based on conjugation lock-in reinforcement to construct sulfur-heteropolycyclic covalent organic frameworks (COFs) with asymmetric electron distribution for superior photocatalytic reactions, which is achieved through a consecutive thionation–cyclization–oxidation transformation of N -acylhydrazone precursors using Lawesson’s reagent. Systematic characterization reveals that sulfur incorporation endows the framework with enhanced chemical stability, localized asymmetric electron density, rapid charge carrier migration, efficient exciton dissociation, extended π-conjugation, and a well-defined donor–acceptor architecture, collectively leading to significantly improved photocatalytic activity and durability compared to the original hydrazone-linked COF. Consequently, the modified COF exhibits a H 2 O 2 evolution rate of 5270 μmol g –1 h –1 in pure water, representing a 3-fold enhancement over the precursor COF (1878 μmol g –1 h –1 ) and surpassing most reported organic and inorganic competitors. Moreover, it achieves complete conversion of benzylamine within 1 h under mild blue light-emitting diode irradiation, demonstrating high efficiency in aerobic oxidation catalysis. These findings establish the lock-in reinforcement strategy coupled with electronic structure modulation as a versatile route to designing durable and highly active photocatalysts for demanding synthetic and energy-conversion applications.