Nanoconfinement Engineering of MOF-Derived-Hollow-Heterojunctions Towards Enhanced Photocatalysis

Rational heterostructure design, tailored architectures, and enhanced charge dynamics are key factors for developing efficient photocatalysis for environmental remediation. In this study, we employed a metal–organic framework (MOF)-derived strategy to construct hollow polyhedral bimetallic sulfide heterojunctions (Co₉S₈/Ag₂S) via nanoconfinement engineering. ZIF-67 is transformed into an amorphous cobalt sulfide scaffold, followed by in-situ growth of Ag₂S nanoparticles and subsequent annealing. This process yields a well-defined heterostructure with intimate interfacial contact, facilitating efficient charge separation and transfer. Under UV light irradiation, the Co₉S₈/Ag₂S heterojunction achieves a photocatalytic tetracycline degradation efficiency of 99.3%, significantly outperforming most other different photocatalyst systems. Comprehensive mechanistic studies reveal that a built-in electric field and nanoconfinement effects synergistically modulate the charge transfer dynamics. Density functional theoretical (DFT) computation results have also shown that the electrons were tended to flow from Co₉S₈ to Ag₂S until a new equilibrium was established over the interface. The intensity of overlap between Co, Ag and S elements across the Fermi level (E_f) was enhanced compared with that in Co₉S₈ or Ag₂S, which means that the heterojunction formation facilitated charge transfer between Co₉S₈ and Ag₂S. Overall, this work advances photocatalyst design and illustrates the potential of MOF-derived heterostructures for efficient, sustainable water treatment applications.