Synthesis, characterization and crystal structure analysis of an open-framework zirconium phosphate

A series of syntheses in the HF-ZrO2-P2O5-Pyridine-H2O system have been performed in an attempt to synthesize novel materials with open zirconium phosphate framework structures. One of the resulting products, designated ZrPOF-pyr (\(C5H6N)(4)(H2O)(2)\[Zr12P16O60(OH)(4)F-8]), has been characterized by XRD, SEM and TG-DTA, and its crystal structure determined from powder diffraction data using direct methods (Pnnm, a = 19.1595(2) angstrom, b = 15.1428(1) angstrom, c = 6.61804(6) angstrom). The framework structure, consisting of corner sharing ZrO6, ZrO5F, ZrO4F2, octahedra and PO4 and PO3OH tetrahedra, proved to be identical to that of \(C5H16N2)(2)(H2O)(6)\[Zr12P16O60(OH)(4)F-8], which had been reported previously. In both structures, the terminal P-OH group is disordered. The non-framework species (pyridinium ion and water molecule) could be located in the channels of the framework. Structure solution was also performed using a charge-flipping algorithm, which makes no symmetry assumptions, to verify that the P-OH disorder is inherent to the material and not a result of an incorrectly assumed space group. The phase is thermally stable to 450 degrees C, but transforms to another phase at higher temperatures. (c) 2007 Elsevier Inc. All rights reserved.