Quantification of silanol sites for the most common mesoporous ordered silicas and organosilicas: total versus accessible silanols

Matthias Ide; Mohamad El-Roz; Els De Canck; Aurélie Vicente; Tom Planckaert; Thomas Bogaerts; Isabel Van Driessche; Frédéric Lynen; Veronique Van Speybroeck; Frédéric Thybault-Starzyk; Pascal Van Der Voort

doi:10.1039/C2CP42811C

Quantification of silanol sites for the most common mesoporous ordered silicas and organosilicas: total versus accessible silanols†

Matthias Ide,^a Mohamad El-Roz,^b Els De Canck,^a Aurélie Vicente,^b Tom Planckaert,^a Thomas Bogaerts,^ae Isabel Van Driessche,^c Frédéric Lynen,^d Veronique Van Speybroeck,^e Frédéric Thybault-Starzyk^b and Pascal Van Der Voort*^a

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* Corresponding authors

^a COMOC, Center for Ordered Materials, Organometallics and Catalysis, Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 (S-3), 9000 Ghent, Belgium
E-mail: pascal.vandervoort@ugent.be
Fax: +32 9264 4983
Tel: +32 9264 4442

^b Laboratoire Catalyse et Spectrochimie (LCS), Université de Caen, 6, Bd du Marechal Juin, 14050 Caen Cedex, France

^c Department of Inorganic and Physical Chemistry, Sol-gel Centre for Research on Inorganic Powder and Thin film Synthesis, University of Ghent, Krijgslaan 281 (S-3), 9000 Ghent, Belgium

^d Department of Organic Chemistry, Laboratory of Separation Sciences, University of Ghent, Krijgslaan 281 (S-4), 9000 Ghent, Belgium

^e Center for Molecular Modeling, Ghent University, Technologiepark 903, 9052 Zwijnaarde, Belgium

Abstract

IR and NMR spectroscopy were used to determine the silanol content in the most common mesoporous ordered silicas: MCM-41, MCM-48, SBA-15 and SBA-16. In addition, a spray dried MCM-41 and an ethene bridged PMO are investigated. The results are compared with a commercial chromatographic silica (Nucleosil). The complete distribution of surface and bulk silanols, and of isolated, geminal and vicinal silanols for all these materials is presented. A distinction is made between the total silanol number and the reachable or surface silanol content. The latter is determined by controlled reactions with simple silanes. All mesoporous ordered silicas, and especially the thick walled SBA-type materials and the PMO contain a surprisingly high amount of total silanol sites, albeit that up to 90% of these silanols are buried inside the walls and are not reachable for small silanes.

Physical Chemistry Chemical Physics

Quantification of silanol sites for the most common mesoporous ordered silicas and organosilicas: total versus accessible silanols†

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Quantification of silanol sites for the most common mesoporous ordered silicas and organosilicas: total versus accessible silanols

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