THE REACTION OF MOLTEN PHENYLPHOSPHONIC ACID WITH A LAYERED DOUBLE HYDROXIDE AND ITS CALCINED OXIDE

Phenylphosphonic acid was thermally intercalated into both the host Mg -Al-CO3 layered double hydroxide (LDH) and its corresponding oxide mat erial (LDO) formed by the thermal decomposition of the host LDH via a novel slow heating method. In the thermal intercalation process, the h ost and guest reactants are carefully heated together to a temperature just above the melting point of the guest. The resulting intercalatio n compounds were studied by a variety of analytical techniques. Powder X-ray diffraction (PXRD) indicated that the reaction products were al l polyphasic microcrystalline materials and suggested that arrangement of the phenylphosphonate anions between the LDH and LDO layers was si milar to that exhibited by zirconium (IV) bis(benzenephosphonate), alp ha-Zr(C6H5PO3)(2) formed via a topotactic reaction. Fourier-transforme d infrared (FTIR) was inconclusive, while thermal analysis of the reac tion mixture clearly showed the reaction taking place. Al-27, C-13 and P-31 solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR) indicated the presence of the anion of phenylphosphonic acid tog ether with some free/unintercalated acid. Collectively, these techniqu es suggested that the phosphonic acid was intercalated between the lay ers of both LDH and LDO hosts by way of an acid-base condensation reac tion.