The structure of a fluorinated gallium phosphate templated with N,N,N′,N′-tetramethylethylenediamine: Ga3(PO4)3F, 0.5N2C6H18 (MIL-20)

Abstract A new three-dimensional open-framework fluorinated gallium phosphate, Ga 3 (PO 4 ) 3 F, 0.5N 2 C 6 H 18 (MIL-20) was prepared from a fluoride-containing aqueous medium in the presence of N,N,N′,N′-tetramethylethylenediamine [(CH 3 ) 2 N(CH 2 ) 2 N(CH 3 ) 2 ] as structure-directing agent. This phase was synthesized hydrothermally (autogenous pressure) at 180°C for 2 days. Its structure was determined by means of single-crystal X-ray diffraction analysis with the following crystal data: P 2 1 / n (No. 14), a =8.861(3) A, b =18.624(5) A, c =9.329(3) A, β =118.27(2)°, V =1355.9(7) A 3 , Z =4, R 1 ( F )=0.0408, wR 2 ( F 2 )=0.1074 for 2805 reflections I >2 σ ( I ) and 211 refined parameters. It is built up from the connection of GaO 4 and PO 4 tetrahedra and GaO 4 F 2 octahedra by corner-sharing. It is based on the stacking of TO 4 -connected layers (T=Ga, P) containing hexagonal rings linked to each other by bioctahedral species Ga 2 O 8 F 2 . The latter unit corresponds to two GaO 4 F 2 octahedra sharing a fluorine common edge. An additional phosphate group is also connected between the TO 4 layer and the dimeric entity. The organic template was found in the cross-linking eight-ring channels running along [100], [001] and [101]. The thermal analysis indicates that the inorganic framework collapses above 420°C after the removal of the template.