Construction and fabrication of Zn(In_0.1Ga_0.9)₂O₄/NH₂-MIL-125(Ti-Zr) composite materials with S-scheme heterojunction for highly efficient photocatalytic degradation of organic pollutants

The effective degradation of organic dyes and tetracycline in wastewater is crucial for environmental protection. Currently, photocatalytic degradation using S-scheme heterojunction catalysts represents an efficient solution. In this study, we employed doping engineering by partially substituting Ga³⁺ with In³⁺ in ZnGa₂O₄ and Ti⁴⁺ with Zr⁴⁺ in NH₂-MIL-125(Ti) to modulate their band edge positions and bandgaps. This approach successfully constructed an S-scheme Zn(In_0.1Ga_0.9)₂O₄/NH₂-MIL-125(Ti-Zr) composite photocatalyst with enhanced built-in electric field. The composite photocatalysts were synthesized via a hydrothermal together with a solvothermal method. Field emission SEM images of the samples showed that the disc-shaped NH₂-MIL-125(Ti-Zr) was effectively attached to the irregular small particles of Zn(In_0.1Ga_0.9)₂O₄. The existence of an S-scheme heterojunction at the interface of Zn(In_0.1Ga_0.9)₂O₄ and NH₂-MIL-125 (Ti-Zr) was confirmed through various characterization techniques, including photoelectrochemical tests, XPS analysis, and free radical trapping experiments. As demonstrated by photocatalytic experiments, the NZ-20 % composite has the highest photocatalytic activity and good stability. The degradation efficiencies for Rh. B and tetracycline over the NZ-20 % composite sample under solar light irradiation for 90 min are 96.3 % and 88.5 %, respectively. Additionally, the response surface methodology (RSM) was employed to analyze the key factors affecting the photocatalytic degradation of organic pollutants, namely pH value, temperature, and contaminant level. All in all, this work presents a potential strategy to fabricate superior composite photocatalysts with S-scheme heterojunctions for combating environmental pollution challenges.