Publications

Probing water dynamics in octahedral molecular sieves: High speed 1H MAS NMR investigations

Alam, Todd M.; Pless, Jason; Nenoff, T.M.

The water dynamics in a series of Sandia octahedral molecular sieves (SOMS) were investigated using high speed 1H magic angle spinning (MAS) NMR spectroscopy. For these materials both the 20% Ti-substituted material, Na 2Nb1.6Ti0.4(OH)0.4O 5.6·H2O and the 0% exchanged end member, Na 2Nb2O6·H2O were studied. By combining direct one dimensional (1D) MAS NMR experiments with double quantum (DQ) filtered MAS NMR experiments different water environments within the materials were identified based on differences in mobility. Two dimensional (2D) DQ correlation experiments were used to extract the DQ spinning sideband patterns allowing the residual 1H-1H homonuclear dipolar coupling to be measured. From these DQ experiments the effective order parameters for the different water environments were calculated. The water environments in the two different SOMS compositions investigated revealed very large differences in the water mobility. © 2007 Materials Research Society.