Preparation of nitrogen and fluorine co-doped mesoporous TiO2 microsphere and photodegradation of acid orange 7 under visible light

N and F-codoped TiO2 microspheres were prepared by ethanol solvothermal method, using tetrabutyl titanate as precursor, urea as a nitrogen source and ammonium fluoride as a fluorine source. The prepared catalysts were characterized by X-ray diffraction (XRD), N2 physical adsorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible adsorption spectroscopy and photoluminescence spectra (PL). The photocatalytic performance of N–F–TiO2 microspheres was evaluated by analyzing the degradation of acid orange 7 (AO7) under visible light irradiation. It was found that N–F–TiO2 microsphere with mesoporous structure is composed by anatase phase, and the interstitial doping of nitrogen into TiO2 lattice might be responsible for the visible light response. Meanwhile, F-doping could not only retard the transformation from anatase to rutile, but also increase the concentration of OH radicals in solution, which is beneficial for improving the photodegradation rate of organic compounds. The synergetic effect of nitrogen and fluorine doping leads to the high activity of N–F–TiO2 for the photodegradation of AO7 under visible light irradiation.