Doping can result in energy band rearrangement, high carrier concentration and fast carrier separation in semiconductor materials. Consequently, great enhancement in the photocatalytic performance can be achieved. In this work, Al3+\documentclass[12pt]{minimal}
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\begin{document}$$\hbox {Al}^{3+}$$\end{document}-doped niobium oxyfluoride (Nb3O7F\documentclass[12pt]{minimal}
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\begin{document}$$\hbox {Nb}_{3}\mathrm{O}_{7}\hbox {F}$$\end{document}) was synthesized by a facile hydrothermal approach for the first time. A series of characterization tools were used to investigate the phase, composition, microstructure, chemical state, spectrum response and band gap. The influence of Al doping on the photocatalytic performance was also investigated by varying the molar ratios of Al/Nb. The results confirmed that Al atoms have been successfully incorporated into the Nb3O7F\documentclass[12pt]{minimal}
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\begin{document}$$\hbox {Nb}_{3}\mathrm{O}_{7}\hbox {F}$$\end{document} lattice. Al doping led to slightly lowering of the band gap of Nb3O7F\documentclass[12pt]{minimal}
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\begin{document}$$\hbox {Nb}_{3}\mathrm{O}_{7}\hbox {F}$$\end{document} from 3.08 to 2.99 eV. Moreover, Nb3O7F\documentclass[12pt]{minimal}
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\begin{document}$$\hbox {Nb}_{3}\mathrm{O}_{7}\hbox {F}$$\end{document} with 0.06 mol% Al doping exhibited the highest degradation efficiency for methyl blue under visible light irradiation. Crystal defects generated by appropriate Al-doping increased the specific surface area and the optimized band gap could be responsible for the improved photocatalytic activity.
