Constructing 2D/2D N-ZnO/g-C3N4 S-scheme heterojunction: efficient photocatalytic performance for norfloxacin degradation

Abstract The low separation efficiency of carriers limited the application of g-C3N4 (CN) in the photodegradation of fluoroquinolones antibiotics, and the construction of two-dimensional/two-dimensional (2D/2D) heterojunction was an effective strategy. In this paper, 2D/2D N-ZnO/CN S-scheme heterojunction composites (x NZCN, x was the mass ratio of ZIF-L/CN) were prepared by calcining ZIF-L/CN composites which were formed via ultrasonic-assisted electrostatic self-assembly method. The photodegradation efficiencies of norfloxacin (NOR), enrofloxacin, levofloxacin, and ciprofloxacin reached more than 90% in 90 min by 15% NZCN/vis system. Moreover, the rate constant of 15% NZCN for photodegrading NOR was 4.15 times and 4.65 times higher than CN and N-ZnO, respectively. The efficient photocatalytic performance of 15% NZCN was attributed to the excellent light capture capacity and the effective migration and separation of carriers. The active species that worked in the photodegradation of NOR were dominated by holes and superoxide radicals. In addition, degradation pathways of NOR were proposed. This work enriched 2D/2D heterojunction engineering for CN, and provided a new possibility for combining 2D MOFs-derivatives with CN to solve the antibiotic pollution problem in the environment.