NH2-MIL-125(Ti)/TiO2 composites as superior visible-light photocatalysts for selective oxidation of cyclohexane

Semiconductor-metal-organic framework (MOF) hybrid photocatalysts have aroused increasing interest because of their enhanced photocatalytic activity. In this work, NH2-MIL-125(Ti)/TiO2 composites with different molar ratios were successfully prepared by a facile one-pot solvothermal method and used for visible-light driven photocatalytic selective oxidation of cyclohexane. The as-prepared NH2-MIL-125(Ti)/TiO2 composites presented better catalytic performances compared with NH2-MIL-125(Ti). This is due to the energy bands coupling and intimate interfacial contact between NH2-MIL-125(Ti) and TiO2, which can improve the photon-generated carrier transfer and minimize the recombination of electron-hole pairs. For the optimum composite photo catalyst, the activity was three times higher than that of NH2-MIL-125(Ti) in visible-light driven photocatalytic cyclohexane oxidation using molecular oxygen as oxidant at room temperature and under ambient pressure. Additionally, the effects of illumination time on the photocatalytic performance and reusability of the optimum composite photocatalyst were investigated in detail. Finally, a possible reaction mechanism has been proposed based on controlling experiments using different radical scavenger techniques, which prove that the photo-generated holes are significantly involved in the oxidation process.