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

Dehydrated aluminumdodecatungstophosphate (AlPW12O40) was investigated by 27Al MAS NMR spectroscopy in magnetic fields of 9.4 and 17.6 T. 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 573 K is accompanied by a partially irreversible change of the oxygen coordination of aluminum cations.