Phenanthridine-based Covalent Organic Frameworks for Boosting Overall Solar HO Production.

Solar-driven HO production via the oxygen reduction reaction (ORR) and water oxidation reaction (WOR) dual channels is green and sustainable but severely restricted by the sluggish reaction kinetics. Constructing intriguing photocatalysts with effective active centers is a shortcut to breaking the kinetic bottleneck with great significance. Herein, we synthesize two novel neutral phenanthridine-based covalent organic frameworks (PD-COF1 and PD-COF2) for photosynthesizing HO. Compared to the no phenanthridine counterpart (AN-COF), the HO photosynthetic activities of PD-COF1 and PD-COF2 are markedly boosted. In air and pure water without sacrificial agents, under Xe lamp and natural sunlight, the HO photogeneration rate of PD-COF2 is 6103 and 3646 μmol g h, respectively. Further experimental and theoretical inspections demonstrate that introducing phenanthridine units into COFs smoothly modulates the charge carrier dynamics and thermodynamically favors the generation of crucial OOH* and OH* intermediates in the ORR and WOR paths, respectively. Additionally, this is the first time the neutral phenanthridine moiety serves as the photooxidation unit for 2e WOR towards HO photoproduction. The current work sheds light on exploring novel catalytic centers for high-performance HO evolution.