Towards the potential of cyano and amino acid-based ionic liquid mixtures for facilitated CO₂ transport membranes

Aiming at developing improved liquid phases for facilitated CO₂ separation from post-combustion processes through supported ionic liquid membranes (SILMs), this work explores the use of binary equimolar IL mixtures containing a common imidazolium cation combined with tricyanomethane and five amino acid-based anions, glycinate, l-alaninate, taurinate, l-serinate and l-prolinate. The CO₂ and N₂ permeation properties of the prepared SILMs were determined at T=318.15 K and several trans-membrane pressure differentials. The results indicate that as the trans-membrane pressure differential decrease, the CO₂ permeability through the SILMs containing the IL mixtures approaches or even surpasses that of the pure [C₂mim][C(CN)₃]. Similarly, the CO₂/N₂ permselectivity significantly increases, meaning that the prepared IL mixtures work as CO₂ carriers under low trans-membrane pressure differentials, facilitating the flux of CO₂ through SILMs. In particular, large CO₂ permeabilities and high CO₂/N₂ permselectivities were obtained for the IL mixtures containing l-alaninate and taurinate anions, indicating that they can be considered as promising and efficient liquid phases for facilitated CO₂ separation.