Synthesis of Ionic Liquid Silica Composite Adsorbents

A conventional ionic liquid, 1-methyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmim][Tf2N]), has been successfully impregnated by physical adsorption into the ordered mesoporous silicas MCM-41 and SBA-15.  For MCM-41, mixed solutions of polar protic and polar aprotic solvents provide selective solvation of the IL and can overcome pore diffusion limitations caused by self-association of the IL and steric hindrance.  Proper selection of the mixed solvents allows for the control of the amount of ionic liquid confined within the pores. Materials were prepared in dry environments using a Schlenk line and in ambient conditions using incipient wetness.  The materials have been characterized with X-ray diffraction, nitrogen isotherms, and thermal gravimetric analysis.  Carbon dioxide, hexane, and water adsorption isotherms of MCM-41, the bulk ionic liquid, and the composite material have been measured to determine composite sorption effects.  The materials are complex and the gas adsorption isotherms reflect both adsorption on the silica support and the solubility of the gas in the ionic liquid.