Coordination of Electron Transfer and Proton Supply in Conjugated Polymer Frameworks for Efficient Hydrogen Peroxide Photosynthesis.

Hydrogen peroxide (H2O2) is a versatile green oxidant and energy carrier, yet its solar production from water and oxygen is limited by the kinetic mismatch between water oxidation and oxygen reduction, as well as insufficient coordination between photogenerated electrons and proton delivery. Here, we report conjugated bithiophene frameworks (CBFs) that integrate molecularly differentiated redox motifs with alkynyl-regulated electron-proton coordination for efficient H2O2 photosynthesis. Progressive extension of alkynyl bridges from CBF-TB to CBF-TDB induces an intraframework excited-state redox polarization that biases photogenerated holes toward benzene/alkynyl motifs and electrons toward thiophene units, facilitating water oxidation and oxygen reduction, respectively. Simultaneously, the alkynyl-rich framework organizes interfacial water into a hydrogen-bonded network that facilitates proton delivery to the oxygen reduction interface. The resulting synergy between directional charge transport and localized proton supply promotes proton-coupled two-electron oxygen reduction to H2O2. Consequently, CBF-TDB achieves a solar-to-chemical conversion efficiency of 1.01% under simulated solar irradiation, more than 4 times that of the alkynyl-free analogue CBF-TB (0.21%). This study establishes the coordinated regulation of excited-state charge polarization and interfacial proton delivery as a molecular design principle for efficient H2O2 photosynthesis and, more broadly, multistep solar-to-chemical conversions.