MOF-derived magnetically recoverable Z-scheme ZnFe2O4/Fe2O3 perforated nanotube for efficient photocatalytic ciprofloxacin removal

Constructing advanced direct Z-scheme photocatalysts is an effective strategy to enhance photogenerated charge separation for photocatalytic removal of organic pollutants but faces challenges in efficient morphology control and recovery method. Herein, a novel magnetically recoverable Z-scheme ZnFe2O4/Fe2O3 perforated nanotube was successfully prepared by one-step MOF-derived calcination method by using MIL-88B/Zn core/shell nanorod as precursor for the first time. In the calcination process, MIL-88B core reacted with oxygen to form hollow Fe2O3 and Zn2+ shell underwent an in situ solid-state reaction with Fe2O3 to cause volume shrinkage and formation of ZnFe2O4, and finally turned into intimate ZnFe2O4/Fe2O3 perforated nanotube (ZFF). Because of such exquisitely perforated nanotube and Z-scheme transfer pathway, ZFF shows superior light absorption, bulk-phase and interfacial separation of photogenerated charge, and thus lead to prominent photocatalytic performance for ciprofloxacin (CIP) removal. Especially, ZFF-2 exhibits the best photocatalytic CIP degradation performance with a degradation percentage of 96.5% and a TOC removal percentage up to 89% under light irradiation for 180 min. Moreover, ZFF show sufficient photo-stability and re-usability for photocatalytic degradation of CIP by a convenient magnetic recovery method. The electron spin resonance experiments, radical trapping and fluorescence experiments reveal that the photogenerated charge pathways of ZFF photocatalysts is a Z-scheme mechanism and the major active species for degradation of CIP are center dot O2- and center dot OH. This work offers a new perspective on construction of high-efficient direct Z-scheme photocatalysts with convenient recovery and deep insight on pollutants purification mechanism.