Synthesis and Crystal Structures of Zirconium Phosphate Fluorides with New 2D and 3D Structure Types

Three new zirconium phosphate fluorides, [amH2]0.5 [Zr2(PO4)(HPO4)2F2]·0.5H2O (1), [amH2]1.5[Zr3(PO4)3F6]·1.5H2O (2) (am=trans-1,4-diaminocyclohexane for 1 and 2), and [amH2]0.5[Zr3(PO4)3(HPO4)F2]·1.5H2O (am=2,2-dimethyl-1,3diaminopropane) (3), were synthesized under hydrothermal conditions and structurally characterized. Zr is octahedrally coordinated in all three structures. In 1, the octahedra consist of ZrO6 and ZrO4F2 units. Compound 2 is made exclusively of ZrO4F2. In 3, there are three different types of Zr-octahedra, namely, ZrO6, ZrO5F, and ZrO4F2. The Zr octahedra and PO4 tetrahedra are connected via non-OH oxygen atoms. In 1 and 2, all F atoms are terminal, whereas in 3, one of the two F atoms bridges between the ZrO5F and ZrO4F2 octahedra. In structures 1 and 2 with higher F/Zr ratios, two-dimensional inorganic networks exist. The inorganic sheets are connected by the protonated templates via N–H···F and in 1 additionally by O–H···F hydrogen bonds. In 3, the lower F/Zr ratio results in the formation of a three-dimensional inorganic framework with characteristic "double" channels in which the highly disordered templates are located. The existence of several structure types in the ZrPOF-n family is discussed on the basis of different template geometry and F/Zr ratios.