SOLID-STATE DEUTERIUM NMR-STUDIES OF ORGANIC-MOLECULES IN THE TECTOSILICATE NONASIL

Solid-state deuterium NMR spectroscopy is used to study the dynamics o f organic molecules occluded in the as-synthesized high-silica tectosi licate nonasil. The nonasil samples are synthesized using trimethylalk ylammonium structure-directing agents to determine the role of electro static interactions. Size effects are quantified by performing H-2 NMR spin-lattice (T-1) relaxation experiments, and the mobility of the su bstituent alkyl groups is studied using H-2 MAS NMR. The charge-compen sating defect sites are characterized using Si-29 and H-1 NMR. The mot ion of the trimethylammonium group of the structure-directing agent is a composite motion of methyl group rotations and rotation about the n itrogen C-3 axis in all samples down to 190 K. The H-2 T-1 and H-2 MAS NMR results illustrate the steric confinement the nonasil cage exerts on the larger (C-n greater than or equal to C-5) subsequent alkyl gro ups. Isotropic motion is not observed for any of the structure-directi ng agents at 370 K, indicating strong organic-inorganic interactions. This is in sharp contrast to nonasil samples made with electrically ne utral amines where rapid isotropic reorientation is observed at room t emperature. These results have interesting implications in zeolite syn thesis. For aluminosilicates synthesized with charged structure-direct ing agents, similar organic-inorganic interactions may allow for alumi num preferentially occupying specific framework sites. This could lead to tailoring the distribution of catalytic sites in zeolites based on the charge distribution of the structure-directing agent.