title: Quantification of silanol sites for the most common mesoporous ordered silicas and organosilicas: total versus accessible silanols.
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.
authors.affiliation: COMOC, Center for Ordered Materials, Organometallics and Catalysis, Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 (S-3), 9000 Ghent, Belgium.
authors.forename: Matthias
authors.initials: M
authors.lastname: Ide
authors.forename: Mohamad
authors.initials: M
authors.lastname: El-Roz
authors.forename: Els
authors.initials: E
authors.lastname: De Canck
authors.forename: Aurélie
authors.initials: A
authors.lastname: Vicente
authors.forename: Tom
authors.initials: T
authors.lastname: Planckaert
authors.forename: Thomas
authors.initials: T
authors.lastname: Bogaerts
authors.forename: Isabel
authors.initials: I
authors.lastname: Van Driessche
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lynen
authors.forename: Veronique
authors.initials: V
authors.lastname: Van Speybroeck
authors.forename: Frédéric
authors.initials: F
authors.lastname: Thybault-Starzyk
authors.forename: Pascal
authors.initials: P
authors.lastname: Van Der Voort