Regulation of β-ketoenamine COFs planarity for enhanced photocatalytic oxidation/dehydrogenation performance

• Synthesized three β -ketoenamine COFs with precisely tuned planarity. • Enhanced visible-light absorption and charge separation/migration through optimized molecular planarity in TP-EDDA-COF. • Exceptional photocatalytic conversions of 98 % (THQ) and 99 % (BA) achieved via charge behavior improvement. • Unveiled planarity's critical role in promoting charge separation via experiments and theory. • Established a clear structure-activity relationship guiding the rational design of high-performance COF photocatalysts. The planarity of covalent organic frameworks (COFs) is a critical structural parameter for their photocatalytic performance. However, its influence on the efficiency of photocatalytic organic transformations has not been fully investigated. Herein, three β -ketoenamine COFs with different planarity, denoted as TP-EDDA-COF, TP-DATP-COF, and TP-DMTP-COF, were synthesized to explore the influence of planarity on their photocatalytic performance. With the best planarity, TP-EDDA-COF exhibited a superior visible-light absorption range and photogenerated carrier separation and migration efficiency. Therefore, it demonstrated exceptional photocatalytic performance, with conversions reaching 98 % for the dehydrogenation of tetrahydroquinoline (THQ) and 99 % for the oxidative coupling of benzylamine (BA). Furthermore, TP-EDDA-COF also exhibited excellent substrate scope and recyclability. Comprehensive material characterization and theoretical calculations revealed that the enhanced planarity significantly facilitated charge separation and migration, thereby leading to improved photocatalytic efficiency. This study deepens the understanding of structure-activity relationships for COF photocatalysts, and provides a theoretical foundation for the rational design of high-performance photocatalysts for aerobic reactions.