Evaluating Biocompatible Amino Acid-Based Poly(ionic liquid)s for CO2 Absorption

Amino acid-based ionic liquids are biocompatible agents which showed a potential for CO2 adsorption. On the other hand poly(ionic liquid)s were showed high adsorption capacity than corresponds ionic liquids. Therefore in this work, for the first time seven biocompatible poly(ionic liquid)s based on amino acids (AAPIL), i.e., alanine [Ala], glycine [Gly], proline [Pro], valine [Val], arginine [Arg], histidine [Hist], and lysine [Lys], were synthesized and characterized, and their CO2 absorption capacities were investigated using the quartz crystal microbalance (QCM) at temperatures of 288.15–308.15 and pressures up to 5 bar. The results showed that the AAPILs are capable to capturing CO2 more than PILs due to functionalized amine tethered at the anion. Based on the absorption mechanism, the reaction equilibrium thermodynamic model is applied to correlating the experimental CO2 absorption capacities. The thermodynamic parameters including reaction equilibrium constants, Henry’s law constants, and enthalpy of physical dissolution were obtained to calculate the amino acids-based poly (ionic liquid) application potential for capturing CO2. The obtained results imply that CO2 absorption capacity increases with increase in pressure and reduce in temperature. Results indicate that number of amino groups is responsible for their absorption capacities. Amongst the studied AAPILs, the highest CO2 absorption capacity was gotten with P[VIm][Arg] due to the availability of more amino groups. Besides, the chemical absorption of CO2 by carbamate formation is confirmed using FT-IR spectroscopy.