Synthesis of Fluoro-Functionalized Mesoporous Silica and Application to Fluorophilic Separations

Fluorocarbon-functionalized mesoporous silica is synthesized by the co-condensation of tetraalkoxysilane and fluoro-functionalized alkoxysilane precursors using a cationic fluorocarbon surfactant, C₆F₁₃C₂H₂NC₅H₅Cl (HFOPC) and C₈F₁₇C₂H₂NC₅H₅Cl (HFDePC), or a traditional hydrocarbon surfactant (C₁₆H₃₃N(CH₃)₃Br, CTAB) as templates. Fluorocarbon functionalization decreases the silica pore order, pore size, and surface area. The chain length of the fluorocarbon functional precursor and the surfactant template affects the pore order, the materials textural properties, and the fluorocarbon incorporation. Matching a fluorocarbon surfactant with a fluorocarbon functional precursor does not improve functional group incorporation; the incorporation of the perfluoro-octyl functional group is greater in CTAB-templated silica than in HFOPC-templated silica. The application of these mesoporous silica powders to fluorous separations is demonstrated using hydrocarbon and fluorocarbon-tagged anthraquinones. Dye elution through a packed column of mesoporous silica occurs in a narrower band than that for fluorocarbon-functionalized silica gel, consistent with the high fluorocarbon content and smaller pore and particle sizes of the mesoporous material.