NMFS-Cu showed excellent activity for H₂O₂ photosynthesis with a nearly 2% solar-to-chemical conversion efficiency. The single-atom Cu sites in NMFS-Cu promote the formation of Cu-μ-peroxide (Cu-O₂ ⁻) and desorption of *H₂O₂, leading to an efficient 2e⁻ ORR pathway. The in situ generated O₂ via water oxidation reaction is rapidly consumed by ORR resulting in a boosted photocatalytic generation of H₂O₂.

Abstract

Hydrogen peroxide (H₂O₂) is a green oxidant widely used in a variety of industries. Photocatalytic generation of H₂O₂ from water and oxygen by sunlight is an appealing strategy compared to the high energy consumption of the industrial anthraquinone process. However, the low activity and selectivity of the two-step single-electron oxygen reduction reaction (ORR) during the photocatalytic process greatly restricts the H₂O₂ production efficiency. Here, we demonstrated that the redox centers in MOFs (NMFS-M, single-atom M linked to an iron-oxo cluster in NH₂-MIL-101(Fe) by a molecular linker cysteine, M = Co, Ni, Cu, and Zn) for the production of H₂O₂ from water and oxygen. The optimal NMFS-Cu stably generates H₂O₂ under simulated sunlight irradiation with a nearly 2% solar-to-chemical conversion efficiency under AM1.5 spectrum and an apparent quantum yield of 19.6% at 420 nm. Combined with density functional theory calculations, isotopic experiments, and advanced spectroscopic characterizations, the high photocatalytic performance is ascribed to the notably promoted sequential two-step ORR to H₂O₂ by forming μ-peroxide and desorption of *H₂O₂ at the single-atom Cu sites. The in situ generated O₂ via water oxidation reaction is rapidly consumed by ORR, leading to a boosted photocatalytic generation of H₂O₂.