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-H2dhb=3,4-dihydroxybenzoic acid). Powder X-ray diffraction (XRD) showed that the basal spacing increased from 8.7 to 8.9 Å for the precursor materials to 15.0 Å 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 °C, show that the 15 Å phase is stable up to about 160 °C. Slightly above this temperature, partial dehydroxylation of the double hydroxide layers occurs, and the characteristic (00l) reflections of the pillared phase are lost. The material is X-ray amorphous in the temperature range 230–450 °C.