Coordination activation enhanced photocatalytic performance for levofloxacin degradation over defect-rich WO3 nanosheets

Abstract

The defect-rich ultrathin WO3 nanosheets are successfully prepared as photocatalysts via heating treatment for the pristine WO3 nanosheets (NS) in vacuum (NSV) and N2 atmosphere (NSN). The increment of degradation efficiencies of levofloxacin (LVX) over NS (49.9 %) <NSN (75.9 %) <NSV (84.3 %) under visible light is mainly due to the increase of oxygen vacancies (OVS). These OVS have the potential to generate more unsaturated W centers (Lewis acid sites) which are beneficial to activate the CO of carboxyl and the C-N of piperazinyl in LVX molecules via W…OC and W…N-C coordination. LC-MS result further demonstrates that the LVX molecules breakdown are mainly initiated by cleaving the activated CO and C-N bonds. More OVS can adsorb and activate more O2 molecules which shall be converted to •O2− by photogenerated electron. The photogenerated holes are transferred on the catalysts surface to form •OH via oxidizing water or directly degrade the activated LVX molecules. Finally, a possible mechanism is proposed to understand the pathway for photocatalytic degradation LVX at molecular scale. This study highlights the significant role of coordination activation for the photocatalytic degradation of antibiotics.