Remarkably Enhanced Photodegradation of Organic Pollutants by NH2-UiO-66/ZnO Composite under Visible-Light Irradiation

Semiconductor photocatalysis is a novel highly efficient and low-cost method for removing organic pollutants from wastewater. However, the photoreduction performance of semiconductors on organic pollutants is limited due to the weak absorption of visible light caused by its wide band gap and low carrier utilization rate resulting from severe electron-holes recombination. In the present study, flower-like NH2-UiO-66 (NU66)/ZnO nanocomposites were prepared using a facile method and exhibited high efficiency under visible light driven photocatalysts. The X-ray diffractometer (XRD), scanning electron microscope (SEM), transmitor electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the prepared samples, indicating that NU66/ZnO was successfully synthesized. The photocatalytic activity of the prepared NU66/ZnO nanocomposites was determined by measuring the photodegradation of methylene blue (MB) and malachite green (MG) under visible-light irradiation. The optimal nanocomposite loading of 5% wt NU66 to NU66/ZnO demonstrated the highest photocatalytic activity for the degradation of MB. The photocatalytic activity of a 5% NU66/ZnO composite was approximately 95-fold and 19-fold higher than that of NU66 and ZnO samples, respectively. The enhanced activity of the 5% wt NU66/ZnO nanocomposite was further confirmed through photoelectrochemical analysis. The formation of type II heterojunctions between the counterparts significantly suppressed recombination of the photogenerated charge carriers. Photocatalytic degradation experiments with different quenchers indicated that the effect of superoxide anion radicals (center dot O-2(-)) had a greater effect than the other scavengers. Additionally, the improved photocatalytic mechanism underlying the activity of NU66/ZnO nanocomposites was also explored. These findings establish a basis for development of MOF based heterojunction for photocatalytic organic pollution remediation.