Symmetry-Based 29Si Dipolar Recoupling Magic Angle Spinning NMR Spectroscopy:  A New Method for Investigating Three-Dimensional Structures of Zeolite Frameworks

• Published in: Journal of the American Chemical Society 2005-01, Vol.127 (2), p.542-543
• Main Authors: Brouwer, Darren H, Kristiansen, Per Eugen, Fyfe, Colin A, Levitt, Malcolm H
• Format: Article
• Language: English
• Subjects: Chemical and knight shifts; Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; General and physical chemistry; Ion-exchange; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Nuclear magnetic resonance and relaxation; Physics; Surface physical chemistry; Zeolites: preparations and properties
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja043228l

A new 29Si solid-state MAS NMR experiment is described for investigating the framework structures of pure silica zeolites. The symmetry-based homonuclear dipolar recoupling sequence SR264 11 has been incorporated into a two-dimensional NMR experiment to probe the Si−O−Si bonding connectivities and long-range Si−Si distances in zeolite frameworks. This dipolar recoupling sequence is shown to have a number of advantages over the J-coupling-based INADEQUATE experiment. For the clathrasil Sigma-2, it is demonstrated that there is excellent agreement between experimental double-quantum build-up curves obtained from a series of two-dimensional double-quantum correlation spectra and simulated curves which consider all Si−Si distances out to 8 Å. This result suggests that this experiment could be used to solve zeolite frameworks with unknown structures.