Spatial Confinement of Photogenerated Electrons at Catalytic Sites in Covalent Organic Frameworks for Efficient Photocatalytic H2O2 Production.

Solar-driven synthesis of hydrogen peroxide (H2O2) offers a sustainable pathway for storing renewable energy using only water and oxygen (O2). Yet its efficiency is often constrained because photogenerated electrons recombine before reaching the O2-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 O2, occurring prior to electron-hole recombination. The efficient charge utilization results in markedly enhanced photocatalytic activity. As a result, BT-Bpy-COF achieves an H2O2 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.