Synthesis and characterization of surface-modified mesoporous silica materials with β-cyclodextrin

Mesoporous silica materials containing microporous cavities provided by surface-bound beta-cyclodextrin (CD ICS) were synthesized by co-condensation of a beta-CD-functionalized triethoxysilane (CD ICL) with TEOS using dodecylamine, tetradecylamine, or hexadecylamine surfactants as structure directing agents. The incorporation of beta-CD within the mesoporous framework was supported by IR, Raman, MALDI TOF MS, C-13 solids CP-MAS NMR, and TGA results. Small-angle X-ray diffraction and nitrogen adsorption provide evidence of ordered silica mesostructured frameworks. For materials with similar CD loading, the textural properties (surface area and pore volume) doubled as the surfactant changed from dodecylamine (C12) to hexadecylamine (C16). The textural properties decrease with CD loading (2 to 6%). The sorption capacity of gas phase polar and apolar species (nitrogen and methyl chloride) varies along with the adsorption properties in aqueous solution toward p-nitrophenol according to the CD loading (2-6%) and surfactant template employed. Along with gas adsorption of model compounds, the structural effects relate to the surfactant alkyl chain length due to the structure directing effects of the C12 to C16 surfactants. This study reveals the structural contribution of surface modification and framework incorporation of beta-cyclodextrin with mesoporous silica framework materials.