Synthesis and characterization of layered double hydroxides intercalated by an oxomolybdenum complex

Zn,Al-layered double hydroxides (LDHs) intercalated by an anionic oxomolybdenum guest were prepared by ion-exchange of precursor Zn,Al-NO3 LDHs with the complex [NMe4](2)[MoO2(3,4-dhb)(2)] (3,4-H(2)dhb=3,4-dihydroxybenzoic acid). Powder X-ray diffraction (XRD) showed that the basal spacing increased from 8.7 to 8.9 angstrom for the precursor materials to 15.0 angstrom for the pillared hybrids. Elemental analysis and IR/Raman spectroscopy indicated that most of the interlayer nitrate anions were displaced by [MoO2(3,4-dhb)(2)](2-) anions. Powder XRD diagrams of Zn,Al-[MoO2(3,4-dhb)(2)], recorded at increasing temperatures in the range 25-450 degrees C, show that the 15 angstrom phase is stable up to about 160 degrees C. Slightly above this temperature, partial dehydroxylation of the double hydroxide layers occurs, and the characteristic (001) reflections of the pillared phase are lost. The material is X-ray amorphous in the temperature range 230-450 degrees C. (c) 2006 Elsevier Ltd. All rights reserved.