PREPARATION AND CHARACTERIZATION OF ZIRCONIUM-PHOSPHATE DIPHOSPHONATES WITH THE GAMMA-STRUCTURE - A NEW CLASS OF COVALENTLY PILLARED COMPOUNDS

Compounds of general formula ZrPO4(H2PO4)1-x[R(PO3H)2]x/2 . nH2O were prepared by topotactic reaction between gamma-ZrPO4H2PO4 . 2H2O and solutions of diphosphonic acids in water-acetone at 80-degrees-C. In particular, two large batches of gamma-ZrPO4(H2PO4)0.56[C6H4(PO3H)2]0.22 . 2.2H2O and gamma-ZrPO4(H2PO4)0.18[C4H8(PO3H)2]0.41 . 1.3H2O were prepared and characterized. The X-ray powder diffraction patterns of the anhydrous and hydrated compounds, the thermogravimetric curves and the Na+-exchange capacity, as well as a structural model of the covalently pillared zirconium phosphate phenyldiphosphonate with the gamma-structure, are reported and discussed.