Quinone Redox Centers Enable Charge Localization and Oxygen Activation for High-Efficiency H2O2 Photosynthesis in Covalent Organic Frameworks

Abstract

Covalent organic frameworks (COFs) offer a crystalline and designable platform for photocatalytic hydrogen peroxide (H2O2) production, yet their efficiencies are often limited by inefficient utilization of photogenerated charges and the lack of chemically defined oxygen reduction centers. Here we show that quinone redox centers enable charge localization and oxygen activation for high-efficiency H2O2 photosynthesis by constructing a π-conjugated COF platform and directly comparing an anthraquinone-containing COF (AQ-HPTP COF) with an anthracene analogue (AN-HPTP COF) as a non-redox control within an identical hxl topology. Under visible light irradiation, AQ-HPTP COF exhibits an exceptional solar-to-chemical conversion efficiency of 2.10%, making it among the highest-performing COF photocatalysts reported for H2O2 photosynthesis. Spectroscopic characterizations combined with theoretical calculations reveal that quinone incorporation induces pronounced frontier-orbital separation and preferential localization of photoexcited electrons at the center, thereby facilitating charge separation and increasing charge utilization. In addition, proton-coupled reduction of the quinone enhances oxygen binding and promotes efficient and selective oxygen reduction toward H2O2. These results establish a general design principle in which integrating programmable quinone redox centers into COF lattices enables the concurrent optimization of charge dynamics and catalytic activity for solar-to-chemical energy conversion.