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A series of nanocomposites of ionic liquids (ILs) were prepared via a modified sol–gel method. The ILs were physically confined in mesoporous silica gels with 5–40% content. ILs from imidazolium, thiophenium and ammonium with different anions were prepared and used. Characterization using the Brunauer–Emmett–Teller (BET) method, Fourier transform infrared (FT-IR) spectroscopy, temperature-programmed desorption (TPD), differential scanning calorimetry (DSC), inverse gas chromatography (IGC), temperature-controlled Raman and fluorescence emission spectroscopies was conducted to explore any confinement effects. BET results showed that, depending on the ILs and their contents, the average pore diameter of the pure silica gel was 3–12 nm after the confined ILs were removed completely. It was suggested that ILs aggregated on the nanoscale in the mesoporous silica gel. In comparison with bulk ILs and ILs coated onto silica gels (IL/sg), IL nanocomposites (IL–sg) displayed remarkably low specific heat capacities (Cp was in the range 0.3–1.2 Jg-1K-1), disordered vibrational conformations (without phase transitions in the range 100–200 1C), greater interactions with hydrocarbon solutes (adsorption capacities of 0.3–0.4 g per 100 g for confined ILs with CO2 gas), and greatly enhanced fluorescence emission (up to 200 times stronger than bulk ILs). Furthermore, Based on the specific solubility of different compounds, the nanocomposites could also be applied to the separation of CO2 from CO2/N2 mixtures and thiophene from thiophene/octane mixtures.

★★★★☆ Zhang J,Zhang QH,Li XL,et al. Nanocomposites Of Ionic Liquids Confined In Mesoporous Silica Gels: Preparation, Characterization And Performance[J]. Physical Chemistry Chemical Physics,2010,12:1971-1981.

With various RTILs as templates, amorphous mesoporous silica gel materials were synthesized according to a proper sol–gel method. The materials display pore diameter of 3–12 nm, pore volume of 0.4–1.3 cm3/g and BET surface area of 300–800 m2/g. The effect of variations of the anions and cations of ILs, the alkylchain length on imidazolium cation and IL concentration in the reaction system on the pore structure and thermal stability of the silicagel materials was preliminarily studied. It is suggested that, the pore size of silica gel can be tuned by variations of ILs and IL content. The different kind of the anions of ILs could largely impact the properties of the obtained silica gel materials. The mesoporous silica gels with 1-alkyl-3-ethylimidazolium tetrafluoroborate as templates possessed larger pore sizes of 5–12 nm and higher thermal stability than the materials obtained with other ILs as templates.

Keywords: Confined; Ionic liquid; Mesoporous; Silica gel; Sol–gel

★★★☆☆ Zhang J,Ma YB,Shi F,et al. Room Temperature Ionic Liquids As Templates In The Synthesis Of Mesoporous Silica Via A Sol–gel Method[J]. Microporous And Mesoporous Materials,2009,119:97-103.

1-Ethyl-3-methylimidazolium dicyanamide EMImN(CN)2 and S-ethyltetrahydrothiophene dicyanamide EThN(CN)2 physically confined into mesoporous silica gel with pore sizes of 6–8 nm (IL-sg) were synthesized according to a proper sol–gel process. Greatly enhanced fluorescence emissions of dicyanamide based ILs after being confined were exhibited.

★★★☆☆ Zhang J,Zhang QH,Shi F,et al. Greatly Enhanced Fluorescence Of Dicyanamide Anion Based Ionic Liquids Confined Into Mesoporous Silica Gel[J]. Chemical Physics Letters,2008,461:229-234.

The solubilities of C2H4 and CO2 and the interactions of polar and nonpolar solutes with the novel ionic liquids (ILs) 1-butyronitrile-3-methylimidazolium bis(trifluoromethylsulfonyl) imidate (CpMIm[NTf2]), 1-butyronitrile-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imidate (CpMMIm[NTf2]), 1-butyronitrile-3-methylimidazolium dicyanamide (CpMIm[N(CN)2]), 1-butyronitrile-2,3-dimethylimidazolium dicyanamide (CpMMIm-[N(CN)2]), 1-butyl-3-methylimidazolium palmitate (BMIm[n-C16H33COO]), and 1-butyl-3-methylimidazolium stearate (BMIm[n-C18H35COO]) were studied by gas chromatography at infinite dilution at T ) (303.15, 313.15, 323.15, and 333.15) K. Henry’s law constant kH of C2H4 and CO2 gas, infinite dilution activity coefficient γ∞, molar enthalpies of solution ΔsolH∞, and partial molar excess enthalpies of solution ΔHE∞ and of Gibbs energies ΔGE∞ were determined for polar and nonpolar solutes in these novel ILs. Compared with the 1,3-dialkylimidazolium ILs, cyano functional group substitution on the alkyl chain results in a remarkable decrease of the interactions of hydrocarbons. BMIm[n-C16H31OO] and BMIm[n-C18H35OO] demonstrate strong solubilization for both polar and nonpolar solutes. Straight lines of ln Vg versus 1/T and ln γ∞ versus 1/T were obtained for the majority of solutes in the temperature range. BMIm[NTf2] and 1-octyl-3-methylimidazolium tetrafluoroborate (OMIm[BF4]) show much better solubility for thiophene and are better solvents for the separations of thiophene from hydrocarbons.

★★★☆☆ Zhang J,Zhang QH,Qiao BT,et al. Solubilities Of The Gaseous And Liquid Solutes And Their Thermodynamics Of Solubilization In The Novel Room-temperature Ionic Liquids At Infinite Dilution By Gas Chromatography[J]. J. Chem. Eng. Data,2007,52:2277-2283.