The solubility of carbon dioxide in a series of imidazolium-based room-temperature ionic liquids has been determined using a quartz crystal microbalance. Henry's constants were obtained for CO2 in nine different ionic liquids:  1-methyl-3-propylimidazolium bis[trifluoromethylsulfonyl]amide (C3mimTf2N), 1-n-butyl-3-methylimidazolium bis[trifluoromethylsulfonyl]amide (C4mimTf2N), C4mimTf2N with polyethylenimine, 1-n-hexyl-3-methylimidazolium bis[trifluoromethylsulfonyl]amide (C6mimTf2N), 1-methyl-3-n-octylimidazolium bis[trifluoromethylsulfonyl]amide (C8mimTf2N), 1-methyl-3-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)imidazolium bis[trifluoromethylsulfonyl]amide (C8F13mimTf2N), 1,4-dibutyl-3-phenylimidazolium bis[trifluoromethylsulfonyl]amide, 1-butyl-3-phenylimidazolium bis[trifluoromethylsulfonyl]amide, and 1-methyl-3-propylimidazolium hexafluorophosphate (C3mimPF6). All results were obtained at 25 °C with CO2 pressures at or less than 1 bar. A comparison of results helps in understanding the role of chemical structure on the separation capabilities of these materials. Notable among the results is a significantly greater measured CO2 solubility in the ionic liquid having the fluorine-substituted cation as compared to the corresponding ionic liquid with a nonfluorinated cation. CO2 solubility was found to be lower in the ionic liquid containing PF6 - than for the corresponding liquid with Tf2N- anion. Addition of an imine polymer to the ionic liquid did not significantly change CO2 solubility characteristics. The presence of water had a minor effect on CO2 solubility for C8mimTf2N for environments with a relative humidity of 40% or less. Henry's constant for CO2 in C3mimPF6 obtained in this study is in good agreement with previously reported Henry's constant values for CO2 in C4mimPF6 that were obtained by other means. This study not only provides some important thermodynamic property information for these unique materials but also illustrates the utility of using a quartz crystal microbalance to obtain this information.

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Self-assembled mesoporous carbon (MC) materials have been synthesized and tested for application in capacitive deionization (CDI) of saline water. MC was prepared by self-assembly of a triblock copolymer with hydrogen-bonded chains via a phenolic resin, such as resorcinol or phloroglucinol in acidic conditions, followed by carbonization and, in some cases, activation by KOH. Carbon synthesized in this way was ground into powder, from which activated MC sheets were produced. In a variation of this process, after the reaction of triblock copolymer with resorcinol or phloroglucinol, the gel that was formed was used to coat a graphite plate and then carbonized. The coated graphite plate in this case was not activated and was tested to serve as current collector during the CDI process. The performance of these MC materials was compared to that of carbon aerogel for salt concentrations ranging between 1000 ppm and 35,000 ppm. Resorcinol-based MC removed up to 15.2 mg salt per gram of carbon, while carbon aerogel removed 5.8 mg salt per gram of carbon. Phloroglucinol-based MC-coated graphite exhibited the highest ion removal capacity at 21 mg of salt per gram of carbon for 35,000 ppm salt concentration.