Hydrothermal synthesis and characterization of new phosphate-based materials prepared in the presence of 1,4-dimethylpiperazine

Abstract

Two new phosphate-based materials, Mu-23 and Mu-25, are prepared with 1,4-dimethylpiperazine as structure directing agent. Mu-23 is the first two-dimensional fluorinated gallophosphate with a Ga/P molar ratio of 5/4. This new phosphate-based material, with the chemical formula [(C 6 H 15 N 2 )(C 6 H 16 N 2 )Ga 5 F 6 (H 2 O) 2 (PO 4 ) 4 ]⊙4H 2 O, crystallizes in the triclinic space group P-1 with the following unit cell parameters: a=8.735(11) , b=8.864(5) , c=12.636(10) , α=98.36(5)°, β=100.18(8)°, γ=115.84(7)°. The symmetry of the three-dimensional zincophosphate Mu-25, [(C 6 H 16 N 2 )Zn 2 (HPO 4 ) 3 ], is monoclinic (space group P 2 1 /n) with a=8.641(5) , b=14.364(9) , c=12.581(11) , β=96.39(6)°. The layers of the gallophosphate consist of GaO 2 F 3 (H 2 O), GaO 4 F 2 octahedra and GaO 4 , PO 4 tetrahedra which share their oxygen and some of their fluorine atoms. The connectivity scheme of these different polyhedra leads to the formation of 8-membered rings. The framework of Mu-25 results from tetrahedrally coordinated zinc and pphosphorus atoms linked through oxygen vertices. The interrupted framework (presence of P-OH and P=O bondings) displays channels with 4-, 8- and 12-membered ring openings. Structures were determined by single crystal X-ray diffraction and characterized by Solid State NMR spectroscopy, thermogravimetric (TGA) and differential thermal (DTA) analyses.