title: Carboxylic groups in mesoporous silica and ethane-bridged organosilica: effect of the surface on the reactivity.
abstract: Proton-donor ability of carboxylic groups incorporated by co-condensation into SBA-15 and ethane-bridged periodic mesoporous organosilica (PMO) has been studied through IR spectroscopy by dosing ammonia, which forms reversibly COO(-) groups and NH(4)(+) ions. The related equilibrium constants, determined by elaboration of IR data, reveal a lower reactivity of -COOH groups at the surface of PMO than on SBA-15, when the two samples have been outgassed at the same temperature. This finding is interpreted in terms of different dielectric constants and intermolecular interactions engaged with the surface species. Carboxylic groups on ethane-bridged organosilica react with silanols upon thermal treatment at 473 K to form a mixed anhydride species Si-O-C(O)-, at variance with the same groups on SBA-15.
authors.affiliation: Dipartimento di Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino, Corso Duca degli Abruzzi, 24-10125 Torino, Italy.
authors.forename: Sonia
authors.initials: S
authors.lastname: Fiorilli
authors.forename: Beatrice
authors.initials: B
authors.lastname: Camarota
authors.forename: Edoardo
authors.initials: E
authors.lastname: Garrone
authors.forename: Barbara
authors.initials: B
authors.lastname: Onida