Resolving crystallographically distinct tetrahedral sites in silicalite and ZSM-5 by solid-state NMR

Fyfe, C. A.; Gobbi, G. C.; Klinowski, Jacek; Thomas, John Meurig; Ramdas, S.

doi:10.1038/296530a0

Cited by 264 publications

(99 citation statements)

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“…Potassium and calcium could be impurities introduced through sample handling and preparation in our laboratory or at the manufacturer's. The presence of aluminum (presumably as A10,) as impurity is consistent with the results of nmr studies (12).…”

Section: Methodssupporting

confidence: 79%

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Intrazeolite photochemistry. II. Evidence for site inhomogeneity from studies of aromatic ketone phosphorescence

Casal¹,

Scaiano²

1985

Can. J. Chem.

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This paper is dedicated to the memory of Li Xiao-BaiH. L. CASAL and J. C. SCAIANO. Can. J. Chem. 63, 1308 (1985. The luminescent properties of several aromatic ketones included in the hydrophobic zeolite Silicalite have been examined. Acetophenone, benzophenone, and P-phenylpropiophenone show readily detectable phosphorescence; by contrast, valerophenone does not luminesce, but undergoes the Norrish Type 11 reaction. Thus, irradiated samples of valerophenone in Silicalite show phosphorescence due to the accumulation of acetophenone. In the case of P-phenylpropiophenone the triplet lifetime is ca. 100 000 times longer than the solution value, suggesting severe conformational restrictions. Co-inclusion of acetophenone with various substrates and oxygen quenching studies indicate that Silicalite has at least two distinct classes of inclusion sites. In one of them energy transfer processes are rapid and efficient, suggesting a cooperative effect in the inclusion of ketones in these regions of the Silicalite framework.H. L. CASAL et J. C. SCAIANO. Can. J. Chem. 63, 1308Chem. 63, (1985. On Ctudie les propriCtCs luminescentes de plusieurs cttones aromatiques contenues dans la zColite hydrophobe Silicalite. L'acCtophCnone, la benzophknone et la P-phtnylpropiophCnone prksentent une phosphorescence que I'on peut dCceler facilement; par ailleurs, la valCrophenone n'est pas luminescente, mais elle subit une reaction de type Norrish 11. Ainsi, les tchantillons irradiCs de valkrophCnone dans la Silicalite ont une phosphorescence qui provient d'une accumulation d'acCtophknone. Dans le cas de la P-phtnylpropiophenone, le temps de vie du triplet est environ 100 000 fois plus long que la valeur en solution et ceci suggkre la prCsence d'importantes contraintes conformationnelles. La co-inclusion de I'acCtophCnone avec differents substrats et des Ctudes de pikgage d'oxygkne indiquent que la Silicalite a au moins deux classes distinctes de sites d'inclusion. Dans I'un d'eux, le processus de transfert dlCnergie est rapide et efficace; ceci suggZre un effet d'ensemble lors de I'inclusion des cCtones dans ces regions du squelette de la Silicalite.[Traduit par le journal]

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Section: Methodssupporting

confidence: 79%

“…Recent work by Fyfe et al (12) suggests the presence of numerous sites in the case of Silicalite, an observatio? that seems consistent with our preliminary observation of a tr dependence of the phosphorescence intensity.…”

Section: Discussionmentioning

confidence: 99%

Intrazeolite photochemistry. II. Evidence for site inhomogeneity from studies of aromatic ketone phosphorescence

Casal¹,

Scaiano²

1985

Can. J. Chem.

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“…It is highest for the Okamoto allophane (0.21) in which the A1/Si ratio is close to unity, as shown previously by Goodman et al (1985). The AFV-~p values found in this study (58.6-59.8 ppm) are in the range reported for framework silicates (55-65 ppm: Fyfe et al, 1982;Kirkpatrick et al, 1985) and A1TM in peralkaline glasses (58-62 ppm: Oestrike and Kirkpatrick, 1988). It is also close to the chemical shifts observed for the isolated tetrahedral aluminum linked to four A1 octahedra in Al[3 polymers (62 + 1 ppm: Bottero et al, 1987) and for an AI~3 exchanged beidellite (62 ppm: Plee et aL, 1985).…”

Section: A1 Mas Nmr Of Imogolite and Allophanessupporting

confidence: 73%

²⁷Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes

Ildefonse

Kirkpatrick

Montez

et al. 1994

Clays and clay miner.

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Abstract--This paper compares the results of 27A1 nuclear magnetic resonance spectroscopy (NMR) and AI-K-edge X-ray Absorption Near Edge Structure (XANES) of natural imogolite and allophanes and some crystaUine reference minerals. All soil allophanes studied contain 4-coordinated A1 (AlIV). The highest relative proportion of A1TM, 21% of the total AI, was found in Si-rich allophane. This value is close to that found in spring allophanes, which were previously considered to be different from soil allophanes. For a quantitative determination of the AlXV/Alt~ ratio, NMR is more reliable than XANES, because of the sensitivity of the chemical shift to low A1TM concentrations, but XANES may be used even if paramagnetic impurities (mostly Fe) are present. Al-K XANES also yields more information than NMR on the local environment of A1 vi and especially site multiplicity. AI w XANES of imogolite and allophanes are similar regardless of the AI/Si ratio. They yield two well-resolved resonances with maxima near 1568 and 1570 eV, which indicates the presence of a unique A1 vt site by comparison with crystalline references. The presence of only one A1 w site indicates that imogolite and allophanes have an octahedral sheet with a structure similar to 2/1 dioctahedral phyllosilicates but different from gibbsite or kaolinite, previously considered as structural analogues. The 27AltV MAS NMR peak maxima of allophanes are between 58.6 and 59.8 ppm, in the range observed for crystalline and amorphous framework aluminosilicates, and less positive than those of sheet silicates, which are typically in the range 65-75 ppm. 27A1-H 1 CPMAS NMR spectra suggest that both A1TM and A1 vI have A1-O-H linkages.

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“…Fyfe et al 108 discovered that there is more that one different type of Al sites and that the monoclinic form of zeolite ZSM-5 (MFI) has 24 unique T-sites. This discovery gained further importance after Haag et al 109 subsequently demonstrated that the aluminum T-sites are the active sites in ZSM-5.…”

Section: Cation-zeolite Interactionsmentioning

confidence: 99%

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

2008

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Resolving crystallographically distinct tetrahedral sites in silicalite and ZSM-5 by solid-state NMR

Cited by 264 publications

References 11 publications

Intrazeolite photochemistry. II. Evidence for site inhomogeneity from studies of aromatic ketone phosphorescence

Intrazeolite photochemistry. II. Evidence for site inhomogeneity from studies of aromatic ketone phosphorescence

²⁷Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

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Resolving crystallographically distinct tetrahedral sites in silicalite and ZSM-5 by solid-state NMR

Cited by 264 publications

References 11 publications

Intrazeolite photochemistry. II. Evidence for site inhomogeneity from studies of aromatic ketone phosphorescence

Intrazeolite photochemistry. II. Evidence for site inhomogeneity from studies of aromatic ketone phosphorescence

27Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

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²⁷Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes