Terephthalate-decavanadate-pillared hydrotalcite

Figure 4 shows the MAS-NMR spectra of several terephthalate/decavanadate-pillared hydrotalcites. These spectra are consistent with that previously published for (NH4)gVio028 (23). The changes which occur to the decavanadate pillars upon calcination of the pillared hydrotalcite are currently being investigated. It is known, however, that in the case of pillared materials containing as little as 25-30% polyoxometalate pillars the overall layered structure is maintained up to 500°C (Figure 5). 

Figure 5. TEM micrograph of a terephthalate/decavanadate-pillared hydrotalcite (39% decavanadate exchanged) after calcination at 500 .

Table I. Exchange Reactions of Terephthalate-Pillared Hydrotalcite Clays with Decavanadate...

Figure 1. Schematic representation of terephthalate exchange with heptamolybdate and decavanadate in hydrotalcite. Pillared hydrotalcite d-spacings were calculated from models.

Figure 4. Vanadium-51 solid state MAS-NMR of terephthalate-pillared hydrotalcites partially exchanged with decavanadate (a) 39% exch. (b) 60% exch. (c) 91% exch.

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