Dimensional reduction in zirconium phosphate; from layers to ribbons to chains

Abstract

Two new one-dimensional zirconium phosphate fluorides, Zr[(NH₄)₂PO₄]₂F₂·H₂O (1) and Zr(NH₄PO₄)[(NH₄)₂PO₄]F·0.5H₂O (2), have been synthesized via decomposition of zirconium fluoride complexes. Their structures were determined by single crystal and X-ray powder diffraction, respectively. The structure of 1 is made of infinite single chains composed of insular Zr octahedra vertex-linked to four PO₄ tetrahedra. Each zirconium is trans-coordinated to two F atoms. The structure of 2 is composed of double chains that can be seen as two condensed single chains of 1, with the elimination of a fluorine atom from the zirconium coordination sphere. Zirconium is octahedrally coordinated, with three triply connected and two doubly connected phosphate tetrahedra, and with a fluorine atom. The structural connection between 1, 2, and layered α- and γ-zirconium phosphates is discussed and verified by interconversion experiments. 1 was found to convert into 2 after ageing in its mother liquor, while 2 can be converted into α-ZrP in acidic media. 1 and 2 were found to swell and form stable colloidal dispersions on elution with 0.1 M hydrochloric acid solution. These properties make these one-dimensional zirconium phosphates interesting compounds for application in nanocomposite materials synthesis.