Solid-State NMR Study of Various Mono- and Divalent Cation Forms of the Natural Zeolite Natrolite
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SCOPUS
- Title
- Solid-State NMR Study of Various Mono- and Divalent Cation Forms of the Natural Zeolite Natrolite
- Authors
- Park, MB; Vicente, A; Fern; ez, C; Hong, SB
- Date Issued
- 2013-03
- Publisher
- ROYAL SOC CHEMISTRY
- Abstract
- Here we present the one-dimensional Si-29 and Al-27 MAS NMR and two-dimensional Al-27 MQMAS and DQF-STMAS NMR spectra of the monovalent (Na+, K+, Rb+, Cs+ and NH4+) and divalent (Ca2+, Sr2+ and Ba2+) cation forms of the natural zeolite natrolite (framework type NAT) with complete Si-Al ordering over the crystallographically distinct tetrahedral sites and with the same hydration state (hydrated, partially dehydrated or fully dehydrated). In the case of monovalent cation-exchanged natrolites, the differences in their crystal symmetry evidenced by Si-29 MAS NMR were found to be in good agreement with those determined by crystallographic analyses. However, Al-27 DQF-STMAS NMR spectroscopy shows the presence of two distinct Al sites in dehydrated K-NAT, Rb-NAT and NH4-NAT, suggesting that their actual crystal symmetry is lower than the reported one (i.e., orthorhombic Fdd2). The MAS NMR results also show that the space group of hydrated Ca-NAT is lower than that (monoclinic F1d1) of hydrated scolecite, the natural calcium counterpart of natrolite, which is also the case with hydrated Sr-NAT and Ba-NAT. We believe that the unexpected diversity in the crystal symmetry of natrolite caused by exchange of various mono-and divalent ions, as well as by dehydration, may be inherently due to the high framework flexibility of this natural zeolite.
- Keywords
- EXCHANGED NATROLITES; QUADRUPOLAR NUCLEI; MQMAS NMR; DEHYDRATION; SPECTROSCOPY; TEMPERATURE; DIFFRACTION; SCOLECITE; FRAMEWORK; STMAS
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/15037
- DOI
- 10.1039/C3CP44421J
- ISSN
- 1463-9076
- Article Type
- Article
- Citation
- Phys. Chem. Chem. Phys., vol. 15, no. 20, page. 7604 - 7612, 2013-03
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