A MOF-on-MOF strategy to construct double Z-scheme heterojunction for high-performance photocatalytic degradation

Well-organized UiO-66-on-MIL-125 growth onto g-C3N4 nanosheets was developed for ofloxacin (OFL) antibiotics degradation under visible light irradiation (λ > 420 nm). First, NH2-MIL-125 as a host MOF was prepared by a solvothermal method, and then UiO-66 crystals were grown onto the NH2-MIL-125 surface with the same method. Subsequently, g-C3N4 nanosheets were decorated onto Zr-MOF-on-Ti-MOF surface to obtain a new type of the double Z-scheme UiO-66/NH2-MIL-125/g-C3N4 heterojunction. Under visible light irradiation, this double Z-scheme heterojunction acts as a highly efficient photocatalyst for the degradation of OFL with a rate constant of 0.07 min−1, which is about 1.79 times higher than that of pristine UiO-66-on-MIL-125. Also, the findings obtained from radical trapping and EPR indicated that •OH and •O2− play an essential role in OFL photodegradation. The current study provides not only new horizons to architecture MOF on other MOFs but also develops Z-scheme heterojunction materials for removing emerging pollutants from wastewater.