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

Hydrogen peroxide (H₂O₂) 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 O₂ reduction and water oxidation half-reactions, without necessary use of any sacrificial agent, enables green H₂O₂ synthesis from O₂ and/or H₂O, 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 O₂ and H₂O, and particularly enables efficient proton transfer, thereby synergistically improving photogenerated charge carrier separation and surface reaction efficiency. Consequently, COF-S-OH achieves an exceptional H₂O₂ production rate of 10.2 mmol g^-1 h^-1 with a solar-to-chemical conversion efficiency of 2.1%, superior to all the thus far reported photocatalysts for H₂O₂ synthesis. This work underscores the critical importance of carrier separation, active site, and proton supply in photocatalytic H₂O₂ generation, providing guidance for designing and fabricating next-generation photocatalysts.