title: Adsorption of CO2 on amine-functionalised MCM-41: experimental and theoretical studies.
abstract: Adsorption of CO2 on MCM-41 functionalised with [3-(2-aminoethylamino)propyl]trimethoxysilane (MCM-41-N2), N(1)-(3-trimethoxysilylpropyl)diethylenetriamine (MCM-41-N3), 4-aminopyridine (MCM-41-aminopyridine), 4-(methylamino)pyridine (MCM-41-methylaminopyridine) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (MCM-41-guanidine) was investigated. The amine-functionalised materials were characterised by (29)Si and (13)C solid-state nuclear magnetic resonance, N2 adsorption/desorption isotherms, X-ray diffraction and transmission electron microscopy. CO2 adsorption at 1.0 bar and 30 °C showed that the amount of CO2 (nads/mmol g(-1)) adsorbed on MCM-41-N2 and MCM-41-N3 is approximately twice the amount adsorbed on MCM-41. For MCM-41-aminopyridine, MCM-41-methylaminopyridine and MCM-41-guanidine, the CO2 adsorption capacity was smaller than that of MCM-41 at the same conditions. The proton affinity (computed with wB97x-D/6-311++G(d,p)) of the secondary amino groups is higher than that of the primary amino groups; however, the relative stabilities of the primary and secondary carbamates are similar. The differential heat of adsorption decreases as the number of secondary amino groups increases.
authors.affiliation: Instituto de Química, Universidade Federal Fluminense, Campus do Valonguinho, CEP 24020-141, Niterói, Rio de Janeiro, Brazil. cmronconi@id.uff.br.
authors.forename: Thiago Custódio
authors.initials: TC
authors.lastname: dos Santos
authors.forename: Sandrine
authors.initials: S
authors.lastname: Bourrelly
authors.forename: Philip L
authors.initials: PL
authors.lastname: Llewellyn
authors.forename: José Walkimar de M
authors.initials: JW
authors.lastname: Carneiro
authors.forename: Célia Machado
authors.initials: CM
authors.lastname: Ronconi