Fabrication of g-C₃N₄ nanosheet/Bi₅O₇Br/NH₂-MIL-88B (Fe) nanocomposites: Double S-scheme photocatalysts with impressive performance for removal of antibiotics upon visible light

Novel g-C₃N₄ nanosheet/Bi₅O₇Br/NH₂-MIL-88B(Fe) photocatalysts (denoted as GCN-NSh/Bi₅O₇Br/Fe-MOF) with a double S-scheme heterojunctions were synthesized by a facile solvothermal route. The resultant materials were examined by XPS, XRD, SEM, TEM, HRTEM, PL, EDX, FT-IR, UV-vis DRS, photocurrent density, EIS, and BET analyses. After integration of Fe-MOF with GCN-NSh/Bi₅O₇Br, the removal constant of tetracycline over the optimal GCN-NSh/Bi₅O₇Br/Fe-MOF (15%) nanocomposite was promoted 33-times in comparison with the pristine GCN. Furthermore, compared to the pure GCN, the GCN-NSh/Bi₅O₇Br/Fe-MOF (15%) nanocomposite showed supreme photoactivity to azithromycin, metronidazole, and cephalexin removal, which were 36.4, 20.2, and 14.6 times as high as the GCN, respectively. The radical quenching tests showed that ⦁O⁻₂ and h⁺ mainly contributed in the elimination reaction. In addition, the nanocomposite had excellent activity after four successive cycles. According to the developed n-n heterojunctions amongst n-GCN-NSh, n-Bi₅O₇Br, and n-Fe-MOF semiconductors, a double S-scheme charge transfer mechanism was proposed for destruction of the selected antibiotics.