Synergistic Tri-efficiency Enhancement Utilizing Functionalized Covalent Organic Frameworks for Photocatalytic HO Production.

The overall maximization of photocatalytic HO production efficiency urgently requires the comprehensive optimization of each step in multiplex photocatalysis. Despite numerous endeavors, isolated researches focusing on single efficiencies hinder further advancements in overall catalytic activity. In this work, a series of imine-linked COFs (TT-COF-X), incorporating electronically tunable functional groups (X = ─H, ─OMe, ─OH, ─Br), are rationally fabricated for visible-light-driven HO production via a dual-channel pathway involving 2e water oxidation and 2e oxygen reduction. Combined simulations and characterizations reveal that the synergistic modification of functional groups for electronic conjugation and locally intramolecular polarity collectively enhanced light absorption, charge separation and transfer, and interface water-oxygen affinity efficiency. Notably, femtosecond time-resolved transient absorption (fs-TA) reveals that the polarity-induced built-in electric field play a crucial role in facilitating exciton dissociation by reacting BIEF-mediated shallow trapping state. The simultaneously optimal tri-efficiency ultimately results in the highest HO production rate of 3406.25 µmol h g and apparent quantum yields of 8.1% of TT-COF-OH. This study offers an emerging strategy to rational design of photocatalysts from the comprehensive tri-efficiency-oriented perspective.