Has O-17 NMR been established as a spectroscopic tool for zeolite characterization?

Several zeolites of type A, X, and sodalite with Si/Al - 1, the zeolites Y, ZSM-5 and the aluminum phosphate AlPO4-14 isotopically enriched in O-17 were analyzed by means of O-17 NMR in the field of 17.6 T using several solid-state NMR techniques for quadrupole nuclei. O-17 DOR NMR spectra are superior to O-17 3QMAS NMR spectra, featuring a resolution increase by a factor of two and are about equal with respect to the sensitivity. The residual linewidths of the signals in the O-17 DOR and O-17 5QMAS NMR spectra can be explained by a distribution Of the Si-O-Al angles in the zeolites. H-1, Al-27, and Si-29 MAS NMR investigations were performed in addition. It was confirmed that in principle the isotropic 170 chemical shift delta(O-17) decreases with increasing T-O-T bond angle alpha for the zeolites under study. For some zeolites a linear correlation was found, e. g. A and X, for some other.. e.g. sodalite and AlPO4-14, it could not be found. The sensitivity of the 17 0 NMR shift with respect to ion exchange and the adsorption of molecules is discussed including the question how the O-17 NMR shift reflects the basicity of the oxygen framework. Cation-exclianged alumosilicates LSX of Si/Al-ratio I were loaded with small molecules (e.g. pyrrol, formic acid, methyl iodide) for the investigation of the latter problem.