Oxygen coordination of aluminum cations in dehydrated AlPW12O40 investigated by solid-state NMR spectroscopy

Dehydrated aluminumdodecatungstophosphate (AlPW12O40) was investigated by 27AlMASNMR spectroscopy in magnetic fields of 9.4 and 17.6T. Two kinds of octahedrally coordinated, two kinds of penta-coordinated, and a small amount of tetrahedrally coordinated aluminum cations were found. Comparison with 1H MAS NMR spectroscopic studies indicates that the dehydroxylation of aluminum OH groups at temperatures of 473 and 573K is accompanied by a partially irreversible change of the oxygen coordination of aluminum cations.