Isopolymetalate-pillared hydrotalcites

Drezdzon, M. A. (1988). Synthesis of isopolymetalate-pillared hydrotalcite via organic-anion-pillared precursors. Inorg. Chem. 27, 4628. 

This paper summarizes work done on the synthesis and characterization of terephthalate-, isopol3rmetalate-, and terephthalate/isopolymetalate-pillared hydrotalcites. Several test... 

Synthesis and Characterization of Isopolymetalate-Pillared Hvdrotalcites. Exchange of terephthalate-pillared hydrotalcite with the appropriate metalate under mildly acidic conditions (pH =4.5) proceeds smoothly to yield the corresponding isopolymetalate-pillared hydrotalcite, as indicated by X-ray diffraction and elemental analysis. The d-spacings of the products confirm that the shortest dimension of the isopolymetalate is perpendicular to the metal hydroxide layers. 

Previously reported methods for synthesizing polyoxometalate-pillared hydrotalcites involve the exchange of chloride-containing hydrotalcites (21-23). In this work, the novel approach taken in synthesizing pillared hydrotalcites has been to prepare an organic-anion-pillared precursor, which is subsequently exchanged with the appropriate isopolymetalate under mildly acidic conditions (Figure 1). 

Recently, it has been shown that hydrotalcite-type clays interlayered by polyoxometalate anions lead to a new class of pillared materials for selective adsorption and catalysis. The heptamolybdate- and decavanade-pillared hydrotalcite-type clays were synthesized by Drezdzon (1988). An organic-anion-pillared clay precursor was prepared and subsequently exchanged with the appropriate isopolymetalate under mildly acidic conditions (pH = 4.T-4.9). These pillared intercalates were found difficult to obtain in highly crystalline form. This is ascribed to the fact that the Mg and Al hydroxide layers have a basic nature, whereas Mo7024 and anions are stable in acidic conditions. 

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