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The magnesium borate fluoride Mg5(BO3)3F was grown by spontaneous crystallization with molten flux based on the MgF2-LiFNa2CO3-H3BO3 solvent.Structure solution from single-crystal X-ray diffraction shows that the title compound crystallizes in the orthorhombic space group Pnma(No.62)with cell dimensions of a = 10.068(5)-,b = 14.858(7)(A),c = 4.540(2)(A) And Z = 4.Its structure features a three-dimensional(3D)Mg-O-F framework composed of MgO5F and MgO6 polyhedra and isolated BO3 groups.The detailed structure comparison referred to Mg5(BO3)3F,Mg3BO3F3 and β-Mg2BO3F was carried out.The infrared spectrum(IR)and the bond valence sum(BVS)calculations of Mg5(BO3)3F verify the validity of the structure.The calculated band structure and the density of states of Mg5(BO3)3F suggest that its indirect bandgap is 5.27 eV.The compound was additionally investigated by UV/Vis-NIR diffuse reflectance spectroscopy and thermal analysis.