Development of Novel Protic Ionic Liquid Gels Applied for CO₂ Separation Materials

Abstract

Ionic liquids are salts, and their melting points were less than 100 ºC under atmospheric pressure. In particular, ionic liquids, which melting point of them were less than room temperature under atmospheric pressure, have been researched in recent decades. Ionic liquids are well-known to designer’s solvents since configuration of cation and anion are easily to change then specificity is exhibited. In this work, novel protic ionic liquids (PILs) which are applied for CO2 sorption materials have been synthesized using aromatic amine such as alkylpyridine derivatives and N,N-dimethylaniline and bis (trifluoromethanesulfonyl) amide due to co-existing proton conductivity and hydrophobicity. Synthesized PILs exhibited hydrophobicity since 1-octanol–water partition coefficients were more than 0. Also, their ionic conductivities were approximately 10−3 S cm−1 at room temperature, and their mechanism of ionic conduction were different one compared with general electrolyte solution due to high viscosities. In addition, several PILs were high selectivity for CO2 sorption compared with N2. Furthermore, PILs gelatinized with bis[4-(1H,1H,2H,2H-tridecafluorooctyl)phenyl] terephthalates due to improvement of mobility. Some of gel–sol transition temperatures of 5 wt% gels were approximately 100 ºC. The driving force of gelation with ionic liquids might be an entropy driven. Sorption selectivity for CO2 and N2 were similar one before and after gelation.