Abstract: Photocatalytic H₂O₂ production from H₂O and O₂ offers a sustainable route but is hindered by the limitations of single-component catalysts, such as narrow light absorption and rapid charge recombination. To address this, an organic/inorganic composite S-scheme heterojunction is constructed through the in-situ growth of In₂S₃ nanosheets on a covalent organic framework (COF), synergistically enhancing light harvesting, carrier separation, and redox capacity. In-situ irradiated XPS, femtosecond transient absorption (fs-TA) spectroscopy, and density functional theory (DFT) calculations jointly reveal the charge transfer dynamics of the COF/In₂S₃ composite. As a result, the optimized S-scheme heterojunction achieves a remarkable H₂O₂ production rate of 5713.2 µmol g^-1 h^-1 in pure water. This work advances the design of S-scheme heterojunction design for optimizing COF-based photocatalysts and deepens the understanding of molecular energy-level engineering.

Key words: Organic/inorganic composite, COF, S-scheme heterojunction, Charge transfer dynamics, In-situ irradiated XPS