Molecular fusion in covalent organic frameworks promotes oxygen reduction and water oxidation for efficient photocatalytic H2O2 production

Abstract

Covalent organic frameworks (COFs) have attracted much attention as photocatalysts for efficient hydrogen peroxide (H₂O₂) production. Herein, we propose a molecular fusion strategy to extend planar conjugated structures to significantly enhance H₂O₂ production performance from O₂ and H₂O. We synthesized BTS-COF and BTT-COF using 5,5′,5″-(benzene-1,3,5-triyl)tris(thiophene-2-carbaldehyde) and benzo[1,2-b:3,4-b′:5,6-b″]trithiophene-2,5,8-tricarbaldehyde as building blocks. BTT-COF exhibits excellent photocatalytic performance with a H₂O₂ production rate of 2904 µmol g⁻¹ h⁻¹, which is higher than that of BTS-COF (1786 µmol g⁻¹ h⁻¹). Experimental and theoretical investigations show that the fused ring structure in BTT-COF can greatly enhance the photoexcited charge transfer and change the local electronic structure. BTT-COF adopts the Pauling-type oxygen adsorption, which has lower adsorption energy. Unexpectedly, the water oxidation reaction (WOR) process of BTS-COF adopts a 4e⁻ pathway. The WOR process of BTT-COF is transformed from 4e⁻ to 2e⁻, thus improving the atom utilization efficiency and enhancing the photocatalytic H₂O₂ production performance. In addition, the antipathogenic concentration of H₂O₂ produced by BTT-COF at minimum inhibitory concentrations (MICs) can kill E. coli and S. aureus (100 µg mL⁻¹) by destroying the bacterial membranes, making BTT-COF a strong candidate as a novel nano-based antimicrobial material. This work provides valuable insights into the design and synthesis of efficient COF-based photocatalysts, and broadens the application of COFs in the antibacterial field, providing new strategies for developing advanced anti-infective materials in the future.