Sacrificial-free H₂O₂ photosynthesis on organic-inorganic core-shell heterojunction under visible light irradiation

Artificial photosynthesis is a promising way to change light energy into chemical energy stored in hydrogen peroxide (H₂O₂). However, numerous heterojunction-based photocatalytic systems have substantially restricted effective H₂O₂ generation due to the intrinsic tendency toward fast charge recombination and the deficiency in active site population on the catalyst surface, especially under conditions not employing sacrificial agents. This study in situ prepared ZnIn₂S₄ (ZIS) nanoflowers onto a hollow covalent organic framework to strategically engineer a type-II organic-inorganic core-shell heterojunction photocatalyst, transforming O₂ into H₂O₂. The heterojunction photocatalyst exhibited an exceptional H₂O₂ productivity of 3334 μmol g^-1h^-1 when no sacrificial agent was added, surpassing most reported systems. Mechanistic studies revealed that the heterojunctions extended the light absorption spectrum toward longer wavelengths and significantly increased the probability of electron transfer from photogenerated carriers to reactive species, which accelerated the reduction of O₂ to H₂O₂. Furthermore, theoretical calculations confirmed that the heterojunction formation modified the coordination environment of the active sites on ZIS, fine-tuned the binding interaction between O₂ and the catalyst interface, and reduced the energy barrier of intermediates, leading to superior performance. This study designed a novel, highly efficient organic-inorganic core-shell heterojunction photocatalyst and provided a promising strategy for enhancing the O₂-to-H₂O₂ conversion.