Construction of a hollow BiOI/TiO2/ZIF-8 heterojunction: Enhanced photocatalytic performance for norfloxacin degradation and mechanistic insight

The overuse of norfloxacin (NOR) has attracted wide attention because of the persistence and bio-accumulate in ecosystems and the negative impacts on human health. To solve the environmental issue, BiOI/TiO2 p-n heterojunctions have been developed and decorated with a porous ZIF-8 to obtain novel hollow BiOI/TiO2/ZIF-8 heterojunctions, which were further characterized by XRD, SEM, HRTEM, XPS, BET, UV–vis DRS, photoluminescence, ESR, photocurrent and EIS analyses. The BiOI/TiO2/ZIF-8 heterojunctions exhibited evidently improved photocatalytic performance compared with pristine BiOI, TiO2 and BiOI/TiO2 composites under visible light irradiation. ZIF-8 plays a key role in both the enhancement of adsorption and the photocatalytic activity in NOR removal. ·O2- and ·OH radicals were the two dominating active species in the photocatalytic process according to the trapping experiments. In 2-BTZ system, large specific surface area, highly effective charge carrier migration with inhibiting recombination, more negative CB and positive VB to generate more active ·O2- and ·OH species resulted in superior photocatalytic activity. This work provides a new idea to design a kind of photocatalytic heterostructure with more active species for potential application in the field of environmental treatment. •A series of hollow BiOI/TiO2/ZIF-8 heterojunctions have been obtained with improved photocatalytic activities.•The ·O2- and ·OH radicals should be the two dominating active species according to the trapping experiments.•Decorating porous ZIF-8 improves adsorption performance and achieves the more efficient hole-charge transfer.•In 2-BTZ system, it can provide more negative CB and more positive VB to generate more active ·O2- and ·OH species.