Enhancing the Photocatalytic Reduction of O₂ to H₂O₂ Through Proton Enrichment on Covalent Organic Frameworks

Increasing the concentration of reagents in chemical reactions is crucial for improving reaction rates. In this study, which focused on the O₂ photocatalytic reduction as a model reaction, a targeted proton enrichment was achieved through the synergistic coordination of imine bonding and pyridazine functional groups in a covalent organic framework. This enhancement resulted in an increased supply of protons during O₂ reduction, leading to the efficient photocatalytic production of H₂O₂. The adjacent distribution of nitrogen atoms provides sites for proton enrichment, and the maintenance of the stability of the protons on the catalyst surface is facilitated by moderate intermolecular forces, thus enabling protons to participate in the O₂ reduction process. The specific reduction mode of the pyridazine functional group, whereby the adsorption of protons is followed by that of O₂, has been shown to significantly enhance the transition from ·O₂ ^- to *OOH. The H₂O₂ yield was determined to be 12,100 µmol g^-1 h^-1, exhibiting a solar chemical conversion efficiency of 2.15%, which is the highest observed value for photocatalysts in pure water. This study provides new insights for improving the efficiency of photocatalytic H₂O₂ production.