High-efficiency photocatalytic degradation of multiple quinolone antibiotics using a hybrid heterojunction with synergistic doping of boron and bismuth

The practical application of conventional photocatalytic technologies in aquatic environmental remediation is significantly limited by rapid charge recombination and insufficient redox capacity. Theoretical calculations and experimental characterization confirmed that the synergistic co-doping of boron (B) and bismuth (Bi) induced tailored modifications to the band structures and Fermi level potential of g-C 3 N 4 (CN) and ZnIn 2 S 4 (ZIS), respectively, successfully transforming the type-II CN/ZIS heterojunction into an S-scheme B-doped CN/Bi-doped ZIS (BCN/BZIS) heterojunction. The subsequent integration of Cd 0.5 Zn 0.5 S (CZS) into the BCN/BZIS heterojunction introduced additional type-II and S-scheme photogenerated carrier transfer pathways, thereby establishing a hybrid BCN/BZIS/CZS heterojunction. This configuration exhibited exceptional reduction capacity and optimized photogenerated carrier separation and migration efficiency, leading to excellent degradation performance for gatifloxacin ((26.89 ± 1.94) × 10 −2  min −1 ), sparfloxacin ((10.48 ± 2.03) × 10 −2  min −1 ), moxifloxacin ((8.43 ± 1.02) × 10 −2  min −1 ), and gemifloxacin ((4.13 ± 0.13) × 10 −2  min −1 ). The degradation disparities among these quinolone antibiotics were systematically elucidated through analyses of steric hindrance, frontier molecular orbital energies, Mulliken charge distribution, reaction sites, and active species contribution rates. This study offers guidance for the systematic development of heterojunction photocatalysts to address fluoroquinolone pharmaceutical pollutants in aquatic ecosystems.