Efficient Photocatalytic Synthesis of H ₂ O ₂ via Spatial Separation Design and Anthraquinone Redox Shuttle in Covalent Organic Frameworks

Abstract

ABSTRACT Covalent organic frameworks (COFs) have emerged as attractive platforms for solar‑driven H 2 O 2 production directly from pure water. However, conventional integrated active‑site architectures that couple oxygen reduction reaction (ORR) and water oxidation reaction (WOR) often suffer from inefficient photogenerated charge separation and severe recombination. Here, we propose a functionality‐coupled spatial separation strategy that integrates site‑isolated redox domains with an anthraquinone (AQ) redox‑shuttle characteristics, exemplified by an AQ‑functionalized COF (BTT‑AQ). Combined experimental and theoretical studies reveal that the benzotrithiophene (BTT) domain acts as a selective two‑electron ORR site, while the AQ domain promotes four‑electron WOR via a hydrogen‑bonded carbonyl‐water network, thereby suppressing charge recombination. In situ diffuse reflectance infrared Fourier transform spectroscopy confirms reversible hydrogenation of AQ to H 2 AQ, which is subsequently oxidized by O 2 to yield H 2 O 2 , establishing a thermodynamically favorable short‑range proton‑transfer pathway for ORR. Without sacrificial agents, BTT‑AQ achieves a remarkable H 2 O 2 production rate of 4218 µmol g −1 h −1 , outperforming redox‐inert analogues BTT‑FO (1368 µmol g −1 h −1 ) and BTT‑AD (532 µmol g −1 h −1 ). This study demonstrates a generalizable design principle that couples spatial charge separation with molecular redox‑shuttle characteristics, paving the way for highly efficient solar H 2 O 2 production.