Synthesis and structure determination of the novel aluminophosphate TL-1 : a new layered compound with corner-sharing AlX6 chains

A novel layered aluminophosphate (TL-1) has been synthesized. Crystals grow as pseudo-hexagonal thin platelets and their whole morphology depends on the synthesis conditions. The structure was solved by single-crystal X-ray diffraction using charge flipping methods. The synthesized layered material, with composition [AlPO4F(H2O)]-(H10C4ON)4, crystallizes in the monoclinic space group P21/a with a=9.2282(5) Å, b=6.9152(4) Å, c=14.4615(9) Å, β=101.57(1)°. The novel compound has corner sharing AlO3F2(H2O) octahedral chains running along [010], where fluorine atoms are at the shared apices, three oxygen atoms are shared with PO4 tetrahedra while the sixth oxygen pertain to an H2O molecule. The stability field of the novel material is enclosed in the HF/Al2O3 ratio ranging between 1 and 4 and the HF/morpholine ratio lower than 3. At temperature lower than 190 °C, the synthesis results is a pure aluminophosphate sample (low alumina/morpholine ratio). A treatment with H2CO3 leads to a complete morpholine removal, as shown by in situ Raman spectroscopy. Powder X-ray diffraction reveals that, after morpholine extraction, the material collapses. The collapse is irreversible.