Spatial Confinement of Photogenerated Electrons at Catalytic Sites in Covalent Organic Frameworks for Efficient Photocatalytic H ₂ O ₂ Production

Abstract

ABSTRACT Solar‐driven synthesis of hydrogen peroxide (H 2 O 2 ) offers a sustainable pathway for storing renewable energy using only water and oxygen (O 2 ). Yet its efficiency is often constrained because photogenerated electrons recombine before reaching the O 2 ‐activation sites. To address this challenge, we developed a thiophene–bipyridine covalent organic framework (BT‐Bpy‐COF) that localizes photoexcited electrons directly at the catalytic centers. Ultrafast transient absorption spectroscopy and Operando X‐ray photoelectron spectroscopy reveal that these confined electrons are rapidly transferred into adsorbed O 2 , occurring prior to electron‐hole recombination. The efficient charge utilization results in markedly enhanced photocatalytic activity. As a result, BT‐Bpy‐COF achieves an H 2 O 2 production rate of 5.3 mmol g −1 h −1 under visible light with an apparent quantum yield of 6.74% at 420 nm and a solar‐to‐chemical conversion efficiency of 0.58%, which is 5.8 times higher than natural photosynthesis. This finding provides a versatile design strategy for advancing high‐efficiency and multi‐electron photocatalysis.