A Z-scheme heterojunction ZIF67/N, P-WO3 nanocomposite for photocatalytic degradation of levofloxacin

Abstract

In this work, a ZIF67/N, P-WO3 (ZNPW) Z-scheme heterojunction was constructed by N, P-codoped WO3 (NPW), and ZIF67 and developed as a highly efficient photocatalyst for Levofloxacin (LFX) removal. A series of characterization measurements including FTIR, XRD, SEM, DRS, PL, and XPS are conducted to confirm the formation of the ZNPW. After optimization on the composition of WO3, NPW and ZIF67, the optimal ZNPW shows superior photocatalytic activity, yielding a higher removal efficiency of LFX ∼91.2% in 100 min than those of pure WO3 (9.4%), NPW (47.8%) and ZIF67 (14.3 %). Additionally, ZNPW exhibits remarkable stability and reusability for up to five consecutive runs. Reactive species scavenging experiments and ESR have revealed that the degradation of LFX is primarily facilitated by the generation of holes (h+) and hydroxyl radicals (·OH). Moreover, the degradation process of LFX was identified through an integrated LC-MS analysis and density functional theory computation of the Fukui indices. This process consists of three pathways: the opening of the piperazinyl ring, separation of piperazinyl and quinoline moieties, and cleavage of the pyridine ring on the quinoline moieties. The superior photocatalytic properties can be attributed to the N, P co-doping in the WO3 structure and the simultaneous coupling with ZIF67, leading to the formation of a heterojunction with a reduced band gap, efficient charge separation and transport, and a new N 2p and P 2p energy level. In conclusion, this study provides novel insights into designing high-efficiency antibiotics degradation using WO3-based Z-scheme heterojunction photocatalysts.