Direct synthesis and accessibility of amine-functionalized mesoporous silica templated using fluorinated surfactants

3-Aminopropyl functionalized silica is synthesized directly using cationic fluorinated surfactants (C₆F₁₃C₂H ₂NC₅H₅Cl (HFOPC) and C₈F ₁₇C₂H₂NC₅H₅Cl (HFDePC)) and a hydrocarbon surfactant (C₁₆H₃₃N(CH₃) ₃Br (CTAB)) as templates. The resulting 3-aminopropyl functionalized silica has a two-dimensional hexagonal pore structure, with greater order and surface area in the CTAB-templated material than the fluorinated-surfactant- templated materials. Greater amine incorporation is achieved using CTAB (1.44 mmol/g), with the least amine incorporation being observed in the HFDePC-templated material (0.92 mmol/g). The incorporation of fluorescein isothiocyanate (FITC) is used to qualitatively probe the accessibility of the amine groups. The reaction of benzaldehyde with the amine groups results in the incorporation of benzaldehyde, which is consistent with the higher accessibility of amines in fluorocarbon-surfactant-templated silica. The interaction of dry CO₂ with amines results in higher CO₂ sorbed in 3-aminopropyl-functionalized silica than nonfunctionalized silica, with greater amine accessibility being observed in the fluorocarbon-templated silica. The incorporation of perfluorooctyl in 3-aminopropyl-functionalized silica reduces the physisorption and CO₂-amine interaction.