NH2-MIL-125(Ti)/amorphous TiO2 microspheres for enhanced visible light photocatalytic selective oxidation of amines

Metal–organic frameworks (MOFs) have received increasing attention for conducting miscellaneous photocatalytic reactions. Amorphous TiO2, despite the lack of visible light activity, can be a platform for integrating with a Ti-based MOF NH2-MIL-125(Ti) during hydrothermal process. Herein, amorphous TiO2 microspheres are synthesized to enhance the activity of NH2-MIL-125(Ti) by integration. The morphology, porosity, and activity of NH2-MIL-125(Ti)/amorphous TiO2 microspheres are systematically investigated by various methods. The photocatalyst NH2-MIL-125(Ti)/amorphous TiO2 exhibits enhanced conversions, more than five times that of pristine NH2-MIL-125(Ti), for the selective oxidation of benzylamine. A series of optical and electrochemical characterizations are performed to clarify the mechanism for the photocatalytic selective oxidation of benzyl amines. Specifically, for NH2-MIL-125(Ti)/amorphous TiO2, visible light absorption is from NH2-MIL-125(Ti); and faster electron transfer to molecular oxygen is due to amorphous TiO2. This work shows that integrating MOFs with metal oxides can be crucial in enhancing visible light photocatalysis.