Applications of silicon-29 NMR spectroscopy

Chemical Shift Anisotropy: A Promising Parameter To Distinguish the 29Si NMR Peaks in Zeolites

“…11 The development of such methodologies in the last decades has contributed to the assignment of the experimental spectra, giving rise to the palette of techniques referred to as 'NMR crystallography.' 12,13 While the 29 Si NMR isotropic chemical shift is one of the most important NMR parameters for zeolites, 14 the partial overlap of signals corresponding to different coordination states is a common problem hindering precise assignments, 5,15 and chemical shift anisotropy was used to distinguish different Q 4 (0Al) 29 Si environments in siliceous zeolites previously. 16,17 In this work, we show that chemical shift anisotropy (CSA) provides a promising parameter to distinguish 29 Si NMR signals of Q 4 species, being either Q 4 (0Al) or Q 4 (1Al) (Brønsted acid sites) and silanols in zeolites.…”