Bioinspired Quinone Redox Cycling Enables Highly Selective Photocatalytic Hydrogen Peroxide Production via Electron-Proton Relay.

Abstract

Solar-driven synthesis of hydrogen peroxide (H₂O₂) is an attractive alternative to the anthraquinone process, yet its practical viability is hindered by poor selectivity and rapid charge recombination. Inspired by quinone-mediated charge management in natural photosynthesis, we design a conjugated polymer, DB-TABQ, embedding redox-active benzoquinone units that drive a light-triggered electron-proton relay catalysis, thereby enabling selective and efficient H₂O₂ production. Upon photoexcitation, the benzoquinone moieties undergo proton-coupled electron transfer to form hydroquinone intermediates that store reducing equivalents as long-lived radical reservoirs. Subsequently, these hydroquinone intermediates adsorb and activate oxygen and initiate an inner-sphere, concerted two-electron transfer to produce H₂O₂ while regenerating the benzoquinone moieties. Spectroscopic characterizations and computational investigations show that this redox-state transformation decouples light absorption from interfacial reaction, promotes directional charge separation, enhances oxygen adsorption, and enables a selective two-electron oxygen reduction pathway, resulting in over 95% selectivity for H₂O₂ production. Notably, DB-TABQ achieves a solar-to-chemical conversion efficiency of 1.34% under simulated solar irradiation. Embedding redox relays into conjugated polymer frameworks offers a general design principle to regulate electron-proton coupling and selectivity in solar-to-chemical conversion.