Constructing π-d interfacial conduction channels in COF-based S-scheme heterojunctions for efficient solar-to-H2O2 conversion

Designing an efficient photocatalytic system capable of facilitating rapid separation and transfer of photogenerated charge carriers is pivotal for enhancing hydrogen peroxide (H₂O₂) production. In this work, a covalent organic framework (COF) was employed as a platform for the in situ growth of Cd_0.6Zn_0.4S (CZS), leading to the formation of a well-defined S-scheme heterojunction. The construction of this hybrid interface enabled strong π–d conjugation between the delocalized π-electrons of the COF and the localized d-orbitals of the semiconductor, significantly reinforcing interfacial electronic interactions and promoting synergistic charge transfer behavior. Comprehensive characterization, including in situ X-ray photoelectron spectroscopy (XPS) analysis, confirmed that this electronic coupling effectively enhanced charge carrier separation and migration. As a result, the oxygen reduction reaction (ORR) was markedly accelerated, yielding a substantial improvement in H₂O₂ production. Under visible light irradiation, the CZS@COF2 photocatalyst achieved an impressive H₂O₂ generation rate of 933.28 μmol g⁻¹ h⁻¹, representing a 3.88-fold enhancement over the pristine COF. Notably, even in pure water without sacrificial agents, the catalyst maintained a high production level of 580.32 μmol g⁻¹, underscoring its excellent photocatalytic performance. Furthermore, the system exhibited robust cycling stability, demonstrating its strong potential for sustainable and practical applications.