Integrating Pd-CNO₂ into covalent organic framework enables efficient H₂O₂ photosynthesis from neutral water

Hydrogen peroxide (H₂O₂) photosynthesis from H₂O and O₂ remains a significant challenge due to the sluggish hydrogen donation process, which stems from the high O-H bond dissociation energy of water. In this study, we propose an effective strategy to accelerate the water oxidation reaction (WOR) by anchoring single palladium atoms (Pd-CNO₂) onto a keto-anthraquinone covalent organic framework (KfAQ-Pd), achieving remarkable H₂O₂ production rates of 3828 μmol h^-1 g^-1 under visible light irradiation (λ > 420 nm) in neutral water. Both experimental observations and theoretical simulations reveal that the Pd-CNO₂ configuration induces an upward shift in the d-band center and enhances the hydrophilicity of KfAQ. This modification effectively disrupts the hydrogen-bond network within adsorbed water clusters, thereby promoting the cleavage of the dangling O-H bonds in H₂O molecules and facilitating efficient hydrogen donation. The generated H₃O⁺ species are subsequently reduced in-situ by photogenerated electrons, leading to the hydrogenation of anthraquinone moieties and ultimately driving efficient H₂O₂ photosynthesis. Overall, these findings highlight the pivotal role of single Pd atoms in enhancing water dissociation and hydrogen transfer, offering a promising new paradigm for solar-driven, environmentally friendly H₂O₂ synthesis in neutral aqueous systems.