Effect of alkyl and aryl substitutions on 1,2,4-triazolium-based ionic liquids for carbon dioxide separation and capture

A series of 1,2,4-triazolium-based ionic liquids have been synthesized and evaluated for their use in supported ionic liquid membrane based CO₂ separations. The properties of these triazolium-based compounds have proven sensitive to isomeric substitutions, such as isopropyl and propyl groups, as well as ortho and para substitutions in the aryl derivative compounds. While physical properties such as viscosity did not vary significantly between structural isomers, the CO₂ permeability, selectivity, and solubility exhibited significant changes allowing for development of task-specific triazolium-based ionic liquids for separation applications. COSMOtherm studies were also completed to gain a better understanding of the ionic liquids which demonstrated a strong correlation between experimental and computational values for the alkyl bearing ionic liquids. Hence, 1,2,4-triazolium-based liquids comprise a class of compounds offering unique opportunities to examine how structural changes affect the physicochemical properties which are necessary for the continuous development of ionic liquids with enhanced adsorption capacity and selectivity in separations.