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

Cuprous oxide (Cu 2 O) 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 Cu 2 O@Cu-HHTP core–shell heterostructure interface for highly efficient PEC sensing of H 2 S. The successful construction of the core–shell Cu 2 O@Cu-HHTP heterostructure is verified by material characterization. In particular, the new HR-TEM images reveal a sharp and coherent interface between the Cu 2 O and Cu-HHTP phases. The optimized interfacial charge transfer between Cu 2 O and the Cu-HHTP shell enables a markedly enhanced photocurrent of 3.81 μA, nearly five times higher than pristine Cu 2 O (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 H 2 S forms Cu 9 S 8 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 H 2 S 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 H 2 S in environmental and biomedical contexts.