In-situ fabrication of TiO2/NH2-MIL-125(Ti) via MOF-driven strategy to promote efficient interfacial effects for enhancing photocatalytic NO removal activity

Deep oxidation of NO molecules to nitrate species by photocatalysis with virtually no toxic byproduct NO2 generation is a challenging task. In this study, TiO2 in-situ grows based on NH2-MIL-125(Ti) (NM-125) not only inhibited TiO2 agglomeration, but also contacted more tightly to obtain efficient interfacial effects, thus displaying excellent photocatalytic NO removal activity (68.08%). The formation of TiO2 is directly confirmed by characterizations such as X-ray diffraction (XRD), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), etc. Meanwhile, UV-vis, photoluminescence, and photoelectrochemical analysis indicate that TiO2 formation effectively improves the optical properties. Moreover, the strong electron interaction and electron transport direction between NM-125 and TiO2 are investigated by density functional theoretical (DFT) calculation. Finally, combined with the results of electron spin resonance (ESR) and in-situ FT-IR test, the intermediate processes of NO adsorption and photocatalytic oxidation reaction are discussed in depth, where the production of reactive oxygen species (ROS) under light is the key factor in the successful degradation of NO. Compared with NM-125 which can only produce •OH through photogenerated electrons since the lower valence band position, NMT-2 can directly produce •OH through photogenerated holes, thereby relieving the pressure on photogenerated electrons and producing more ROS. This study will provide reasonable guidance for the modification of NM-125 for photocatalytic removal of ppb-level NO.