Cu ₂ O@Conductive MOFs Heterostructure with Efficient Photocarrier Separation for Sensitive Photoelectrochemical Detection of H ₂ S

Cuprous oxide (Cu₂O) is a promising photoelectrochemical (PEC) material, but its performance is hindered by poor charge separation and photocorrosion. These limitations can be effectively mitigated by constructing semiconductor heterojunctions that promote interfacial charge transfer and improve structural stability. Herein, we present a type-II Cu₂O@Cu-HHTP core-shell heterostructure interface for highly efficient PEC sensing of H₂S. The successful construction of the core-shell Cu₂O@Cu-HHTP heterostructure is verified by material characterization. In particular, the new HR-TEM images reveal a sharp and coherent interface between the Cu₂O and Cu-HHTP phases. The optimized interfacial charge transfer between Cu₂O and the Cu-HHTP shell enables a markedly enhanced photocurrent of 3.81 μA, nearly five times higher than pristine Cu₂O (0.84 μA). The resulting sensor exhibits an ultralow detection limit of 3.40 nM and an exceptionally broad linear range from 10.0 nM to 100.0 μM. Mechanism studies indicate that exposure to H₂S forms Cu₉S₈ at the heterojunction, which disrupts its structure, accelerates charge recombination, and attenuates the photocurrent. Compared with existing sensing technologies, it demonstrates superior sensitivity and achieves the lowest detection limit reported to date among sensors based on metal oxides or MOFs materials. Enabling accurate detection of endogenous H₂S in rat cerebrospinal fluid through in vivo microdialysis, demonstrating strong potential for biological monitoring. This work highlights an effective interfacial engineering strategy to boost charge separation and broaden detection capability, offering a robust platform for ultrasensitive PEC sensing of H₂S in environmental and biomedical contexts.