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Heteronuclear NMR Spectroscopy as a Surface‐Selective Technique: A Unique Look at the Hydroxyl Groups of γ‐Alumina.
Author(s) -
Taoufik Mostafa,
Szeto Kai C.,
Merle Nicolas,
Rosal Iker Del,
Maron Laurent,
Trébosc Julien,
Tricot Grégory,
Gauvin Régis M.,
Delevoye Laurent
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201304883
Subject(s) - heteronuclear molecule , chemistry , magic angle spinning , nuclear magnetic resonance spectroscopy , spectroscopy , resonance (particle physics) , crystallography , nuclear magnetic resonance , stereochemistry , physics , atomic physics , quantum mechanics
The surface hydroxyl groups of γ‐alumina dehydroxylated at 500 °C were studied by a combination of one‐ and two‐dimensional homo‐ and heteronuclear 1 H and 27 Al NMR spectroscopy at high magnetic field. In particular, by harnessing 1 H– 27 Al dipolar interactions, a high selectivity was achieved in unveiling the topology of the alumina surface. The terminal versus bridging character of the hydroxyl groups observed in the 1 H magic‐angle spinning (MAS) NMR spectrum was demonstrated thanks to 1 H– 27 Al RESPDOR (resonance‐echo saturation‐pulse double‐resonance). In a further step the hydroxyl groups were assigned to their aluminium neighbours thanks to a { 1 H}‐ 27 Al dipolar heteronuclear multiple quantum correlation (D‐HMQC), which was used to establish a first coordination map. Then, in combination with 1 H– 1 H double quantum (DQ) MAS, these elements helped to reveal intimate structural features of the surface hydroxyls. Finally, the nature of a peculiar reactive hydroxyl group was demonstrated following this methodology in the case of CO 2 reactivity with alumina.