A Proton-Responsive Backbone Relay for Selective Two-Electron Oxygen Reduction to H2O2
Efficient photocatalytic H2O2 production in organic polymers requires the coordinated regulation of charge separation, O2 activation, and proton delivery, yet these processes are often optimized independently. Here, we report a postsynthetic thiol–yne editing strategy that converts a passive alkynyl bridge in a donor–acceptor covalent organic polymer into a bridge-adjacent proton-responsive catalytic module. Reaction with mercaptoacetic acid transforms the original C═C linkage into a sulfur-containing unit bearing –SCH2COOH groups, thereby reshaping the local reaction environment rather than simply increasing surface polarity. The edited bridge modulates electronic communication, enhances interfacial hydrophilicity, and introduces a reversible COOH/COO– proton-transfer microenvironment under photocatalytic conditions. Combined experimental and theoretical results show that this click-programmed module promotes photogenerated charge separation, strengthens O2 adsorption and activation, facilitates proton-coupled electron transfer, and stabilizes key *OOH intermediates, directing oxygen reduction toward the selective two-electron pathway. Consequently, the edited polymer CP-COOH achieves an H2O2 production rate of 14.959 mmol g–1 h–1 under sacrificial-agent-free conditions using only water and air, representing a 118.7-fold enhancement over the parent polymer. This work establishes backbone bond editing as an effective strategy for programming local reaction fields in organic photocatalysts.