Fe3O4@MOF-based binary photocatalyst for degradation of Brilliant Green under UV–A and solar irradiation: a study on mineralization, ecotoxicity and real-world water application

This work investigates the removal of Brilliant Green (BG) using ZIF-67- and ZIF-8-based structures as heterogeneous photocatalysts. To further explore catalytic enhancement, Fe 3 O 4 nanoparticles were incorporated into the ZIF structure to evaluate their contribution to the photo-Fenton process. XPS analysis identified characteristic bands corresponding to Co-N, Zn-N, and C-N bonds, along with Fe-O. Diffuse reflectance spectroscopy revealed different distinct band-gap energy transitions in the ZIF-based spectra, supporting the coordination effect of metal ions with the ligand. Incorporation of 4.0 wt% Fe 3 O 4 into ZIF structure significantly enhanced BG degradation, achieving 100% removal under photo-assisted Fenton conditions. In the Fe 3 O 4 @ZIF-67 system, the interfacial charge-transfer dynamics follow a Z-scheme arrangement, whereas the Fe 3 O 4 @ZIF-8 operates through a conventional type-II heterojunction. The O 2 •– was the primary reactive species responsible for the pollutant degradation. BG dye removal in the presence of real water matrices showed minor interference from naturally occurring ions, combined with the partial mineralization achieved. Using sunlight as an energy driver, the optimized system exhibited effective BG dye removal, and the ecotoxicity assay an indication of the treatment's impact on the resulting solution. Fe 3 O 4 @ZIF composites demonstrated catalytic stability over consecutive degradation cycles, as evidenced by the absence of significant spectral changes in FTIR analysis after use. The heterojunction between Fe 3 O 4 and ZIF structures demonstrated excellent efficiency, making them promising candidates for practical use in real-world wastewater treatment systems. Overall, the robust performance, stability, and solar responsiveness of the photocatalysts highlight its broader environmental significance as a scalable solution for advanced pollutant remediation.