CO₂capture in poly(ionic liquid) membranes: atomistic insight into the role of anions

Abstract

We report the first atomistic simulation study to characterize poly(ionic liquid) (PIL) membranes and examine their capability for post-combustion CO(2) capture. Four PILs based on 1-vinyl-3-butylimidazolium ([VBIM](+)) are examined with four different anions, namely bis(trifluoromethylsulfonyl)imide ([TF(2)N](-)), thiocyanate ([SCN](-)), hexafluorophosphate ([PF(6)](-)) and chloride ([Cl](-)). Gas molecules (CO(2) and N(2)) in [VBIM](+)-based PILs interact with polycations more strongly than with anions. Therefore, the role of anions in gas solubility is insignificant, which is in remarkable contrast to monomeric ILs. The solubilities predicted in the four PILs are close and in good agreement with available experimental data. The sorption, diffusion and permeation selectivities of CO(2)/N(2) predicted from simulation are consistent with experiment. Particularly, the diffusion selectivities are approximately equal to one, implying that CO(2)/N(2) separation is governed by sorption. This study provides atomistic insight into the mechanisms of gas sorption, diffusion and permeation in [VBIM](+)-based PILs and reveals that polycations play a dominant role in determining gas-membrane interaction and separation.

Imidazolium‐Based Poly(ionic liquid)s as New Alternatives for CO2 Capture

“…[22,23] Low T g and ion plasticisation are typical for materials with less thermally stabilised microvoids. [22,23] Low T g and ion plasticisation are typical for materials with less thermally stabilised microvoids.…”

“…[10] CO 2 capture capacity depends on the types of polycation and anion, substituents and the polymer backbone. [13,22] In general, ammonium-based PILs were reported to possess higher CO 2 sorption capacity than imidazolium-based PILs, [13,21,23] which might be caused by their more substantial positive charge density that results in stronger interactions with CO 2 . [13,22] In general, ammonium-based PILs were reported to possess higher CO 2 sorption capacity than imidazolium-based PILs, [13,21,23] which might be caused by their more substantial positive charge density that results in stronger interactions with CO 2 .…”

“…and high-capacitance dielectrics, [19] catalyst supports and nanoparticle stabilisers [25] and were found to display high ionic conductivity. [12,13] Methacrylatebased PILs have been investigated for electrochemical applications, [22] and the choice of this polycation was inspired by the use of these PILs as ion-conductive materials. [12,13] Methacrylatebased PILs have been investigated for electrochemical applications, [22] and the choice of this polycation was inspired by the use of these PILs as ion-conductive materials.…”

“…[13,15,21] The type of polycation is considered to be the decisive factor in terms of CO 2 capture performance. [13,22] In general, ammonium-based PILs were reported to possess higher CO 2 sorption capacity than imidazolium-based PILs, [13,21,23] which might be caused by their more substantial positive charge density that results in stronger interactions with CO 2 . At the same time, the difference in capacity of imidazolium-based PILs can be in the order of approximately four to five times.…”

Characterization of Absorption Performance for Gaseous Acetone with Ionic Liquid Solutions

“…The charge of the ILs changes its polarity, which is beneficial for selective dissolution. Therefore, ILs are regarded as environmentally benign green solvents which are applied in many fields [24][25][26][27][28].…”