Synthesis of Paramolybdate Intercalates of Hydrotalcite-like Compounds by Ion Exchange in Ethanol/Water Solution

Highly ordered paramolybdate (Mo 7 O 24 6 - ) intercalates of hydrotalcite-like compounds (HTlcs) were obtained through anion exchange performed on well-crystallized parent HTlcs in an ethanol/water solution. Aqueous solutions of paramolybdate are acidic, causing hydrolysis of HTlcs, but we found that an ethanol/water solution prevented dissolution of magnesium in the host layers and preserved the highly ordered layer structure of parent HTlcs during anion exchange. These highly ordered paramolybdate intercalates were found to change their structures easily at the usual drying temperatures, with the layer structure being transformed after dehydration of the interlayer water at 80 °C. Moreover, the (003) reflection of the XRD pattern for the paramolybdate intercalates obtained in this study was missing, although previous studies report that the (003) peak has been observed for poorly ordered paramolybdate intercalates. A model calculation proved that the (003) peak existed, but was very weak. The large atomic scattering factor of the molybdenum atoms in paramolybdates differentiates their XRD pattern from that of other HTlcs, such as those containing carbonate.