31 P MAS NMR investigation of some microporous zincophosphates

Abstract

High field magic-angle spinning (MAS) 31 P-NMR investigations of novel porous zincophosphates and their cobalt-containing derivatives confirm the framework structure of alternating Zn(Co)O 4 and PO 4 tetrahedra. The MAS NMR spectrum of cobalt-containing products exhibits a large anisotropy manifested in numerous side bands. This effect is attributed to paramagnetic shifts induced by dipolar interactions between the unpaired electrons of Co 2+ and the 31 P nuclei. The relative intensity of the side bands is significantly lower in the cobalt-exchanged sample (where the Co 2+ does not occupy framework sites) than in the cobalt-containing zincophosphates. This shows that 31 P-NMR measurements can give direct evidence of extra-framework cobalt(II) or of Co(II) incorporation in the zincophosphate lattice.