Electron/Proton Transport Engineering in Acylhydrazone-Linked Covalent Organic Framework for Efficient Solar-driven HO Production.

Hydrogen peroxide (HO) is a vital industrial chemical extensively utilized in textiles, pharmaceuticals, and disinfection. Solar-driven photocatalytic technology depending on photocatalysts with matched energy band structure for simultaneously driving both O reduction and water oxidation half-reactions, without necessary use of any sacrificial agent, enables green HO synthesis from O and/or HO, offering a low-energy and simple-operation process without secondary pollution while avoiding safety and environmental risk of conventional methods. Herein, a novel acylhydrazone-linked 2D COF, COF-S-OH, was prepared from benzo[1,2-b:3,4-b':5,6-b'']trithiophene-2,5,8-tricarbaldehyde and 2,3-dihydroxysuccinohydrazide. Both experimental and theoretical analyses reveal that introduction of benzotrithiophene units and hydroxyl groups enhances the electron donor-acceptor effect in COF-S-OH, optimizes the light-harvesting and adsorption capacities to O and HO, and particularly enables efficient proton transfer, thereby synergistically improving photogenerated charge carrier separation and surface reaction efficiency. Consequently, COF-S-OH achieves an exceptional HO production rate of 10.2 mmol g h with a solar-to-chemical conversion efficiency of 2.1%, superior to all the thus far reported photocatalysts for HO synthesis. This work underscores the critical importance of carrier separation, active site, and proton supply in photocatalytic HO generation, providing guidance for designing and fabricating next-generation photocatalysts.