Cation−Anion−CO₂ Interactions in Imidazolium‐Based Ionic Liquid Sorbents

Abstract

A series of functionalized N-alkylimidazolium based ionic liquids (ImILs) were designed, through anion (carboxylates and halogenated) and cation (N-alkyl side chains) structural modifications, and studied as potential sorbents for CO . The sorption capacities of as prepared bare ImILs could be enhanced from 0.20 to 0.60 molar fraction by variation of cation-anion-CO and IL-CO -water interaction. By combining NMR spectroscopy with molecular dynamics simulations, a good description of interactions between ImIL and CO can be obtained. Three types of CO sorption modes have been evidenced depending on the structure of the ImIL ion pair: Physisorption, formation of bicarbonate, and covalent interaction through the nucleophilic addition of CO to the cation or anion. The highest CO sorption capacity was observed with the ImIL containing the 1-n-butyl-3-methylimidazolium cation associated with the carboxylate anions (succinate and malonate). This study provides helpful clues for better understanding the structure-activity relationship of this class of materials and the ion pair influence on CO capture.

Ionic Liquid–Polymer Composites: A New Platform for Multifunctional Applications

“…Further, CO 2 acts as a Lewis acid and the anion as a Lewis base, and the CO 2 solubility is attributed to the proximity of the CO 2 and the anion. [ 65 ]…”

The Nature of Carbon Dioxide in Bare Ionic Liquids

“…[33] The addition of water into the system does not disrupt the coordination patterns, which remain almost unaltered (Figure 3 b). [34] The nonbasic ILs present low sorption capacity under atmospheric pressure (> 0.2 mol CO 2 /mol IL &&should this actually be < 0.2?&&), so this type of IL will not be the main focus of this Minireview. [35][36][37] By contrast, various ILs containing basic anions display multimolar CO 2 sorption (Table 1).…”

“…Allied to the residual water present in the ILs, the flue gas contains a considerable amount of water (e.g., 5-7 % by volume), and understanding a) Spatial distribution functions (SDFs) for the PF 6 anion (green) and CO 2 (red) near the imidazolium cation for the interaction of CO 2 with 1-butyl-3methylimidazolium hexafluorophosphate ([BMIm]PF 6 ) IL (adapted from Corvo et al [32] b) Radial distribution functions (RDFs) corresponding to systems containing IL ([BMIm]Br), CO 2 , and H 2 O. C(CO 2 )-Br(anion) (adapted from Simon et al [34] the effect and the nature of water is critical for post-combustion CO 2 capture and utilization. [47] Conflicting structural attribution of the products resulting from the interaction between CO 2 and ILs is also evident in the case of prolinate-containing ILs (Scheme 2).…”

Direct CO2 Capture and Reduction to High‐End Chemicals with Tetraalkylammonium Borohydrides

“…Dissolving these substrates in organic solvents would resolve the problem of CO 2 diffusion, but avoidance of solvents is the factor that differentiates these materials from NaBH 4 . Increasing solid–gas reactivity while maintaining a capacity of up to three moles of CO 2 per mole of TAAB at ambient conditions makes these materials excellent CO 2 absorbers, with five to six times larger capacity than that of traditional ILs (around 0.5 mol mol −1 at 10–20 bar) [23, 51] …”

“…Dissolving these substrates in organic solvents would resolve the problem of CO 2 diffusion, but avoidance of solvents is the factor that differentiates these materials from NaBH 4 .I ncreasing solid-gas reactivity while maintaining acapacity of up to three moles of CO 2 per mole of TAAB at ambient conditions makes these materials excellent CO 2 absorbers,with five to six times larger capacity than that of traditional ILs (around 0.5 mol mol À1 at 10-20 bar). [23,51] Effect of CO 2 concentration and temperature Low concentration CO 2 capture is primordial in applications like post-combustion capture,i nw hich the CO 2 concentration is about 15 %. [52] Nitrogen was mixed with CO 2 in the MSB to reach various CO 2 concentration:60, 42, 23, and 12 vol%.…”