Heteronuclear NMR Spectroscopy as a Surface‐Selective Technique: A Unique Look at the Hydroxyl Groups of γ‐Alumina. Issue 14 (6th March 2014)

• Record Type: Journal Article
• Authors: Taoufik, Mostafa; Szeto, Kai C.; Merle, Nicolas; Rosal, Iker Del; Maron, Laurent; Trébosc, Julien; Tricot, Grégory; Gauvin, Régis M.; Delevoye, Laurent
• Is Part Of: Chemistry. Volume 20:Issue 14(2014)
• Page Start: 4038
• Page End: 4046
• Publication Date: 2014-03-06
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201304883
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The surface hydroxyl groups of γ‐alumina dehydroxylated at 500 °C were studied by a combination of one‐ and two‐dimensional homo‐ and heteronuclear ¹H and ²⁷Al NMR spectroscopy at high magnetic field. In particular, by harnessing ¹H–²⁷Al 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 ¹H magic‐angle spinning (MAS) NMR spectrum was demonstrated thanks to ¹H–²⁷Al RESPDOR (resonance‐echo saturation‐pulse double‐resonance). In a further step the hydroxyl groups were assigned to their aluminium neighbours thanks to a {¹H}‐²⁷Al dipolar heteronuclear multiple quantum correlation (D‐HMQC), which was used to establish a first coordination map. Then, in combination with ¹H–¹H 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 CO₂ reactivity with alumina.</p> </abstract>