Thermal and Physical Properties of CO₂-Reactive Binary Mixtures

Binary solvent mixtures based on 1-ethyl-3-methylimidazolium 2-cyanopyrrolide, [EMIM][2-CNpyr], an ionic liquid (IL), and a series of hydrogen bond donors (HBDs) including ethylene glycol (EG), propylene glycol (PG), and monoethanolamine (MEA) were characterized in terms of temperature-dependent densities and viscosities along with their thermal stability and CO2 absorption–desorption capability. NMR and FTIR were employed to observe the effect of the IL/HBD composition on intermolecular interactions. Among the investigated mixtures, IL/EG (1:2) showed the most efficient absorption–desorption performance and thermal stability. Though IL/PG and IL/EG had similar CO2 absorption capacities, the IL/PG exhibited the highest viscosity, which limited the CO2 transport in the solvent. The IL/MEA solvent possesses significant CO2 absorbance capability; however, the strong binding energy between MEA and CO2 and the increased viscosity during absorption led to difficulties in CO2 desorption. This study highlights the modification of intermolecular interactions in IL/HBD binary mixtures with respect to the choice of HBDs, reflected by their distinct physical properties and CO2 binding behavior.