Amino acid based poly(ionic liquid) materials for CO₂ capture: Effect of anion

Poly(ionic liquid) materials based on eight amino acids (arginine [Arg], lysine [Lys], histidine [Hist], taurine [Tau], proline [Pro], serine [Ser], alanine [Ala] and glycine [Gly]) have been synthesized and characterized as CO₂ absorbers. Among the broad family studied, [Lys] was found to have the highest gravimetric uptake with 15.7 wt%. In terms of molar adsorption, the highest CO₂ sorption capacity was obtained with [VBTMA][Arg] with 0.83 mol/mol and this increased to 1.14 mol/mol after polymerization. The CO₂ sorption increased as pressure increased and decreased as temperature was increased. Maximum desorption occurred at 80 °C and the materials can be readily recycled with 86% sorption capacity retention demonstrated on the 5th sorption cycle. The molecular-level behavior of the anions was discussed in terms of their activity coefficients and σ-profiles from COSMO-RS calculations.