Solid-state NMR studies of the fluoride-containing zeolite SSZ-44

Magic-angle spinning NMR has been used to probe the local structure of as-made zeolite SFF containing occluded fluoride and NN-diethyl-2,6-dimethylpiperidinium. The Si-F bond distance has been measured using two methods: variable contact time cross polarization studies (1.74 Angstrom) and spinning sideband intensity fitting at relatively slow spinning speeds (1.79 Angstrom). Both measurements yield results that are significantly shorter than the internuclear Si-F distance as measured by single-crystal X-ray diffraction (similar to1.9 Angstrom), which is based on the average positions of the atoms due to disorder and hence does not reflect the true bond distance.