Following the new synthetic strategy recently reported to prepare 3d bimetallic oxyfluorides, Cu3Al2OF10 was synthesized by thermal decomposition under air ambient of the hydrated fluoride Cu3Al2F12(H2O)12 (Fig. ). This precursor was prepared by the co-precipitation of an ethanolic solution of metallic salts in a hydrofluoric acid (HF48%) solution. A detailed description can be found in the supporting information. The X-ray diffraction pattern of microcrystalline powder confirms the trigonal variety of Cu3Al2F12(H2O)12 with a minor presence of its allotropic triclinic variety (7% wt.). Single-crystals of these two varieties were prepared by a slow evaporation of the same mixture. Details of their structural determinations together with atomic positions, atomic displacement parameters and distances are given from Tables . The thermal decomposition of Cu3Al2F12(H2O)12 under ambient air was monitored by thermodiffraction (TXRD) combined thermogravimetric analysis (TGA) (Fig. ). TXRD analysis shows three domains: stability of Cu3Al2F12(H2O)12 (RT-100°C, blue), dehydration leading to the formation of a poorly crystallized/amorphous intermediate (120-360°C, green) and formation of oxides CuO and CuAl2O4 (T > 360°C, red). TGA curve indicates that the dehydration takes place in two steps: (1) and (2). Taking into account the weight loss (experimental %, theoretical %), the formulation of this new oxyfluoride is determined as Cu3Al2OF10. The experimental weight loss of the last step (3) corresponding to the hydrolysis of Cu3Al2OF10 is in good agreement with theoretical value.