Nature and structure of aluminum surface sites grafted on silica from a combination of high-field aluminum-27 solid-state NMR spectroscopy and first-principles calculations

Handle URI:
http://hdl.handle.net/10754/562158
Title:
Nature and structure of aluminum surface sites grafted on silica from a combination of high-field aluminum-27 solid-state NMR spectroscopy and first-principles calculations
Authors:
Kerber, Rachel Nathaniel; Kermagoret, Anthony; Callens, Emmanuel; Florian, Pierre A.; Massiot, Dominique; Lesage, Anne; Copéret, Christophe; Delbecq, Françoise; Rozanska, Xavier; Sautet, Philippe
Abstract:
The determination of the nature and structure of surface sites after chemical modification of large surface area oxides such as silica is a key point for many applications and challenging from a spectroscopic point of view. This has been, for instance, a long-standing problem for silica reacted with alkylaluminum compounds, a system typically studied as a model for a supported methylaluminoxane and aluminum cocatalyst. While 27Al solid-state NMR spectroscopy would be a method of choice, it has been difficult to apply this technique because of large quadrupolar broadenings. Here, from a combined use of the highest stable field NMR instruments (17.6, 20.0, and 23.5 T) and ultrafast magic angle spinning (>60 kHz), high-quality spectra were obtained, allowing isotropic chemical shifts, quadrupolar couplings, and asymmetric parameters to be extracted. Combined with first-principles calculations, these NMR signatures were then assigned to actual structures of surface aluminum sites. For silica (here SBA-15) reacted with triethylaluminum, the surface sites are in fact mainly dinuclear Al species, grafted on the silica surface via either two terminal or two bridging siloxy ligands. Tetrahedral sites, resulting from the incorporation of Al inside the silica matrix, are also seen as minor species. No evidence for putative tri-coordinated Al atoms has been found. © 2012 American Chemical Society.
KAUST Department:
KAUST Catalysis Center (KCC)
Publisher:
American Chemical Society
Journal:
Journal of the American Chemical Society
Issue Date:
18-Apr-2012
DOI:
10.1021/ja3008566
Type:
Article
ISSN:
00027863
Sponsors:
This publication is based on work supported by Award No. UK-00017, made by King Abdullah University of Science and Technology (KAUST), and by the TGE RMN THC Fr3050. The authors thank the PSMN at ENS of Lyon for the attribution of CPU time and Raphael Wischert for sharing data (ref 60).
Appears in Collections:
Articles; KAUST Catalysis Center (KCC)

Full metadata record

DC FieldValue Language
dc.contributor.authorKerber, Rachel Nathanielen
dc.contributor.authorKermagoret, Anthonyen
dc.contributor.authorCallens, Emmanuelen
dc.contributor.authorFlorian, Pierre A.en
dc.contributor.authorMassiot, Dominiqueen
dc.contributor.authorLesage, Anneen
dc.contributor.authorCopéret, Christopheen
dc.contributor.authorDelbecq, Françoiseen
dc.contributor.authorRozanska, Xavieren
dc.contributor.authorSautet, Philippeen
dc.date.accessioned2015-08-03T09:46:08Zen
dc.date.available2015-08-03T09:46:08Zen
dc.date.issued2012-04-18en
dc.identifier.issn00027863en
dc.identifier.doi10.1021/ja3008566en
dc.identifier.urihttp://hdl.handle.net/10754/562158en
dc.description.abstractThe determination of the nature and structure of surface sites after chemical modification of large surface area oxides such as silica is a key point for many applications and challenging from a spectroscopic point of view. This has been, for instance, a long-standing problem for silica reacted with alkylaluminum compounds, a system typically studied as a model for a supported methylaluminoxane and aluminum cocatalyst. While 27Al solid-state NMR spectroscopy would be a method of choice, it has been difficult to apply this technique because of large quadrupolar broadenings. Here, from a combined use of the highest stable field NMR instruments (17.6, 20.0, and 23.5 T) and ultrafast magic angle spinning (>60 kHz), high-quality spectra were obtained, allowing isotropic chemical shifts, quadrupolar couplings, and asymmetric parameters to be extracted. Combined with first-principles calculations, these NMR signatures were then assigned to actual structures of surface aluminum sites. For silica (here SBA-15) reacted with triethylaluminum, the surface sites are in fact mainly dinuclear Al species, grafted on the silica surface via either two terminal or two bridging siloxy ligands. Tetrahedral sites, resulting from the incorporation of Al inside the silica matrix, are also seen as minor species. No evidence for putative tri-coordinated Al atoms has been found. © 2012 American Chemical Society.en
dc.description.sponsorshipThis publication is based on work supported by Award No. UK-00017, made by King Abdullah University of Science and Technology (KAUST), and by the TGE RMN THC Fr3050. The authors thank the PSMN at ENS of Lyon for the attribution of CPU time and Raphael Wischert for sharing data (ref 60).en
dc.publisherAmerican Chemical Societyen
dc.titleNature and structure of aluminum surface sites grafted on silica from a combination of high-field aluminum-27 solid-state NMR spectroscopy and first-principles calculationsen
dc.typeArticleen
dc.contributor.departmentKAUST Catalysis Center (KCC)en
dc.identifier.journalJournal of the American Chemical Societyen
dc.contributor.institutionUniversité de Lyon, CNRS, Ecole Normale Supérieure de Lyon, 46 allée dItalie, F-69364 Lyon Cedex 07, Franceen
dc.contributor.institutionLaboratoire de Chimie Organométallique de Surface, CNRS, Université Lyon 1, CPE Lyon, Franceen
dc.contributor.institutionCEMHTI CNRS UPR3079, Université DOrléans, 1D Avenue de la Recherche-Scientifique, F-45071 Orléans Cedex 2, Franceen
dc.contributor.institutionUniversité de Lyon, Centre de RMN À Très Hauts Champs, UCB-Lyon 1, 5 rue de la Doua, F-69100 Villeurbanne, Franceen
dc.contributor.institutionDepartment of Chemistry, ETH Zürich, Wolfgang-Pauli Strasse 10, CH-8093 Zürich, Switzerlanden
dc.contributor.institutionMaterials Design, 18 rue de Saisset, F-92120 Montrouge, Franceen
kaust.authorCallens, Emmanuelen
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