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91 results on '"McCusker L"'

5. Nomenclature of structural and compositional characteristics of ordered microporous and mesoporous materials with inorganic hosts(IUPAC Recommendations 2001)

Author

McCusker, L. B., Liebau, F., Engelhardt, G., McCusker, L. B., Liebau, F., and Engelhardt, G.

Abstract

A system of terms applicable to ordered microporous and mesoporous materials is proposed, and rules for writing a standardized crystal chemical formula for such materials are presented. The recommendations are based both on common usage and on a systematic classification scheme. The nomenclature has been developed to encompass all inorganic materials with ordered, accessible pores with free diameters of less than 50 nm. The crystal chemical formula describes the chemical composition of both the guest species and the host, the structure of the host, the structure of the pore system, and the symmetry of the material. This formula can be simplified or expanded to suit the user's requirements

Published
2017

12. Structure analysis of the novel microporous aluminophosphate IST-1 using synchrotron powder diffraction data and HETCOR MAS NMR

Author

Jordá, J. L., McCusker, L. B., Baerlocher, C., Morais, C. M., Rocha, J., Fernandez, C., Borges, C., Lourenço, J. P., Ribeiro, M. F., and Gabelica, Z.

Subjects
FOCUS, Poder diffraction, Aluminophosphate, MAS NMR, IST-1
Abstract

A combination of advanced powder diffraction and NMR techniques have allowed the structure of the novel microporous aluminophosphate IST-1 (|(CH3NH2)4(CH3NHþ 3 )4(OH )4|½Al12P12O48 ) to be elucidated. The framework structure was determined in the non-centrosymmetric space group Pca21 (a ¼ 9:61523ð1Þ AA, b ¼ 8:67024ð1Þ AA, c ¼ 16:21957ð2Þ AA) from high-resolution synchrotron powder diffraction data using the program FOCUS. Extra framework species were then located on difference electron density maps. A hydroxyl group was found to bridge between two of the framework Al atoms, and one methylamine species, presumably protonated, could be located in the channels where it H-bonds to three framework oxygens. The most unusual feature of the structure is the second methylamine molecule, which bonds directly to a framework Al atom. The structure is entirely consistent with 31P and 27Al MAS NMR studies, which showed there to be three P (all 4-coordinate) and three Al (one 4-, one 5- and one 6-coordinate) sites, and with 13C MAS NMR, which showed there to be two different types of methylamine species in equal amounts. Assignment of the 31P, 27Al and 13C MAS NMR signals could be deduced from the crystallographic data,31P-27Al HETCOR spectra and ab initio calculations.

Published
2003

25. Structure analysis of a BEC-type germanosilicate zeolite including the location of the flexible organic cations in the channels.

Author

Smeets, S., Koch, L., Mascello, N., Sesseg, J., McCusker, L. B., Hernández-Rodríguez, M., Mitchell, S., and Pérez-Ramírez, J.

Subjects
SILICATES, ZEOLITES, CATIONS, AMINES, CHEMICAL synthesis
Abstract

A BEC-type zeolite (polymorph C of zeolite beta) with low germanium content (Si : Ge = 5.1) has been synthesised using the flexible linear diquaternary cationic form of pentamethyldiethylenetriamine (2,2′-(methylazanediyl)bis(N,N,N-trimethylethanammonium) as the organic structure-directing agent (SDA). The distribution of germanium within the framework and the location of the SDA within the pores have been determined by analysing synchrotron X-ray powder diffraction data collected on the as-synthesised form. The findings, which are corroborated by 13C and 19F NMR data, indicate that the structure of the SDA is retained during the synthesis and that the Ge atoms occupy only sites in the double 4-ring. Although the BEC framework structure has a three-dimensional 12-ring channel system, the SDA molecules are found to orient themselves in two dimensions along the channels running parallel to the a and b axes. [ABSTRACT FROM AUTHOR]

Published
2015
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47. Nomenclature of structural and compositional characteristics of ordered microporous and mesoporous materials with inorganic hosts: (IUPAC recommendations 2001)

Author

McCusker, L. B., Liebau, F., and Engelhardt, G.

Subjects
*CRYSTALS, *MATERIALS
Abstract

A system of terms applicable to ordered microporous and mesoporous materials is proposed, and rules for writing a standardized crystal chemical formula for such materials are presented. The recommendations are based both on common usage and on a systematic classification scheme. The nomenclature has been developed to encompass all inorganic materials with ordered, accessible pores with free diameters of less than 50 nm. The crystal chemical formula describes the chemical composition of both the guest species and the host, the structure of the host, the structure of the pore system, and the symmetry of the material. This formula can be simplified or expanded to suit the user’s requirements. [Copyright &y& Elsevier]

Published
2003
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48. Review and Criticism

Author

Haines, Aleyne Clayton, Stendler, Celia Burns, Freyer, Freda, Rees, Frances, Kenworthy, Leonard S., La Tourette Stockwell, McCusker, L., Thompson, Ralph H., Whitehead, Frances E., Burnett, R. W., Cathon, Laura E., Bough, Helon C., Clark, Lillian Novotny, Rollins, Clarlemae, Bough, Helen C., Zim, H. S., Burnett, R. Hill, Bleeker, Sonia, Hodapp, K. E., Lindahl, Hannah M., Rollins, Charlemae, Novotny, Lillian, Beal, Elizabeth M., Raynor, Elizabeth Lee, Lieberman, Myron, Krarup, Agnes, Hinman, Dorothy, and Zim, Herbert

Published
1952

50. NMR Characterization and Rietveld Refinement of the Structure of Rehydrated AlPO<INF>4</INF>-34

Author

Tuel, A., Caldarelli, S., Meden, A., McCusker, L. B., Baerlocher, C., Ristic, A., Rajic, N., Mali, G., and Kaucic, V.

Abstract

The triclinic form of AlPO4-34, a microporous aluminophosphate with the chabazite (CHA) topology, adopts a rhombohedral symmetry upon calcination. The framework structure of this phase remains intact under ambient conditions, but it distorts dramatically, though reversibly, in the presence of water. Following these structural changes in situ by X-ray diffraction revealed that there are actually two stable rehydrated phases, which differ from each other by one water molecule in the channel. Both of these phases have triclinic unit cells that are closely related to that of the calcined rhombohedral phase. The structure of the low-temperature (10 °C), fully rehydrated phase (phase B) was elucidated by combining high-resolution synchrotron powder diffraction with solid-state NMR techniques. Coordination of three of the six Al atoms to water molecules causes the deformation of the framework and the reduction of the symmetry. Rietveld refinement of the structure of phase B in the triclinic space group P1 (a = 9.026, b = 9.338, c = 9.508 Å, α = 95.1°, β = 104.1°, and γ = 96.6°) converged with RF = 0.079 and RWP = 0.176 (Rexp = 0.087). Framework connectivities derived from the structure were used to assign 31P NMR lines as well as part of the 27Al NMR signal.

Published
2000

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