Optimum conditions for intercalation of lacunary tungstophosphate(V) anions into layered Ni(II)–Zn(II) hydroxyacetate

Acetate containing nickel–zinc hydroxysalts (LHS-Ni–Zn) have been synthesized by coprecipitation and hydrothermal treatment. The acetate anions were exchanged with PW12O403− anions, and optimum conditions to attain the maximum level of W in the compound have been identified. The W intercalated compound was characterized by powder X-ray diffraction, FT-IR spectroscopy, thermogravimetric and differential thermal analyses, scanning electron microscopy and transmission electron microscopy.The exchange of LHS-Ni–Zn with PW12O403− at pH=3 for 72 h leads to a solid with a basal spacing of 9.62 Å and a W content (weight) of 37%. The hydrothermal treatment at 90 °C for 24 h increases this value to 48% with a W/Zn molar ratio of 1.38, which corresponds to a layered compound with lacunary tungstophosphate anions in the interlayer space. The intercalated solid is stable up to 250 °C, the layer structure collapses on dehydroxylation and amorphous compounds were identified at 500 °C. Two crystalline phases, NiO (rock salt) and a solid solution (Zn1−xNix)WO4, were identified by powder X-ray diffraction at high temperature (ca. 1000 °C).

Optimum conditions for intercalation of Keggin-type anions in Ni, Zn hydroxysalts have been identified. Lacunary species are formed via partial depolymerization of the starting anion. The thermal decomposition of the intercalated phases has been also studied.Figure optionsDownload as PowerPoint slide