Novel C/ZnO/ZnFe2O4@ZnIn2S4 double S-scheme heterojunction for efficient photocatalytic degradation of tetracycline hydrochloride

•C/ZnO/ZnFe2O4 was obtained by one-step calcination using bimetallic MOFs as templates, and a double S-scheme heterojunction was constructed by in situ growth of ZnIn2S4.•The direction of the built-in electric field and the transfer path of electrons at the interface of the double S-scheme heterojunction are demonstrated by calculating the work functions.•C as an electronic bridge to accelerate the charge transfer between the interfaces, and the improved photocatalytic performance is attributed to the synergistic effect of the double S-scheme heterojunction and the carbon layer.•The experimental results show that 30 mg of FS-2 showed 96 % removal of 20 mg/L TC.•C/ZnO/ZnFe2O4@ZnIn2S4 can be recycled by applying a magnetic field. In this paper, C/ZnO/ZnFe2O4@ZnIn2S4 ternary heterojunctions were prepared using Zn-Fe bimetal-organic frameworks (Zn-Fe MOFs) as precursors and applied to the photocatalytic degradation of tetracycline hydrochloride (TC). The experimental results show that 30 mg of the composite (FS-2) showed 96 % removal of 20 mg/L TC. The improved photocatalytic performance was attributed to the synergistic effect of the double S-scheme heterojunction and the carbon layer, which greatly facilitated the separation of electron-hole pairs by the reverse motion of electrons and holes driven by the difference of work functions and the built-in electric field at the interface. The carbon layer acts as an electronic bridge can further improve the charge transfer between the interfaces of different photocatalysts, allowing more useful electrons and holes with strong redox capabilities to participate in the surface reactions. Combining the experimental results and density functional theory (DFT) calculations, the photocatalytic mechanism of the dual S-scheme system is proposed. This study provides a theoretical basis for the design of novel photocatalytic materials with dual S-scheme heterojunctions and efficient photocatalytic degradation.