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Location of the fluoride ion in tetrapropylammonium fluoride silicalite-1 determined by H-1/F-19/Si-29 triple resonance CP, REDOR, and TEDOR NMR experiments

TitleLocation of the fluoride ion in tetrapropylammonium fluoride silicalite-1 determined by H-1/F-19/Si-29 triple resonance CP, REDOR, and TEDOR NMR experiments
Publication TypeJournal Article
Year of Publication2001
AuthorsFyfe, CA, Brouwer, DH, Lewis, AR, Chezeau, JM
JournalJournal of the American Chemical Society
Volume123
Pagination6882-6891
Date PublishedJul
Type of ArticleArticle
ISBN Number0002-7863
Keywords3-DIMENSIONAL BONDING CONNECTIVITIES, 5-COORDINATE, CONTAINING OCTADECASIL, CROSS-POLARIZATION NMR, CRYSTAL-STRUCTURE, DETERMINATIONS, DISTANCE, MAS-NMR, NATURAL-ABUNDANCE, PROTON-ENHANCED NMR, SILICON, SOLID-STATE SI-29
Abstract

The location of the fluoride ion in tetrapropylammonium fluoride silicalite-1 ([TPA]-F-[Si-MFI]), an as-synthesized siliceous zeolite with the MEI topology, has been unambiguously determined using solid-state NMR experiments alone. With the H-1 –> Si-29 CP-INADEQUATE experiment, the 12 peaks in the highly resolved Si-29 MAS NMR spectrum of [TPA]-F-[Si-MFI] were assigned. Using these peak assignments it was possible to perform H-1/F-19/Si-29 triple resonance CP, REDOR, and TEDOR experiments to measure F-Si distances and thus locate the fluoride ion. It is covalently bonded to Si-9 in the [4(1)5(2)6(2)] cage of the zeolite framework and exchanges between two "mirror-related" Si-9 sites, making them equivalent on the NMR time scale. The importance of this result and the general applicability of the approach are discussed.

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