Theoretical Analysis of Physical and Chemical CO₂ Absorption by Tri- and Tetraepoxidized Imidazolium Ionic Liquids

Abstract

The efficient capture of CO 2 from flue gas or directly from the atmosphere is a key subject to mitigate global warming, with several chemical and physical absorption methods previously reported. Through polarizable molecular dynamics (MD) simulations and high-level quantum chemical (QC) calculations, the physical and chemical absorption of CO 2 by ionic liquids based on imidazolium cations bearing oxirane groups was investigated. The ability of the imidazolium group to absorb CO 2 was found to be prevalent in both the tri-and tetraepoxidized imidazolium ionic liquids (ILs) with coordination numbers over 2 for CO 2 within the first solvation shell in both systems. Thermodynamic analysis of the addition of CO 2 to convert epoxy groups to cyclic carbonates also indicated that the overall reaction is exergonic for all systems tested, allowing for chemical absorption of CO 2 to also be favored. The rate-determining step of the chemical absorption involved the initial opening of the epoxy ring through addition of the chloride anion and was seen to vary greatly between the epoxy groups tested. Among the groups tested, the less sterically hindered monoepoxy side of the triepoxidized imidazolium was shown to be uniquely capable of undergoing intramolecular hydrogen bonding and thus lowering the barrier required for the intermediate structure to form during the reaction. Overall, this theoretical investigation highlights the potential for epoxidized imidazolium chloride ionic liquids for simultaneous chemical and physical absorption of CO 2 .

Thermodynamics of Tri- and Tetraepoxyimidazolium NTf2 Amine Polyaddition: A Theoretical Perspective

“…Recently, in addition to the previously studied two-site epoxyimidazolium complexes, tri-and tetraepoxyimidazolium compounds have also been synthesized and characterized to give additional epoxy sites to IL−epoxy monomers. 30,38 In this study, it was found that these monomers can give varied results when compared to the standard two-site epoxy IL previously synthesized. In this study, simulations were performed to assess the local domains of the amine−epoxy solution before any polymerization takes place.…”

“…These IL epoxy/amine polymers were found to have a high thermal stability of over 300 °C in addition to a high ionic conductivity and storage modulus, making them ideal for applications as robust polymers capable of retaining and remembering shape. Recently, in addition to the previously studied two-site epoxyimidazolium complexes, tri- and tetraepoxyimidazolium compounds have also been synthesized and characterized to give additional epoxy sites to IL–epoxy monomers. , In this study, it was found that these monomers can give varied results when compared to the standard two-site epoxy IL previously synthesized. In this study, simulations were performed to assess the local domains of the amine–epoxy solution before any polymerization takes place.…”

Epoxidized Ionic Liquids as Processing Auxiliaries of Poly(Lactic Acid) Matrix: Influence on the Manufacture, Structural and Physical Properties

“…In addition, ILs may also offer several advantages, such as low volatility and higher thermal stability, and lower solid-solid migration compared to molecular plasticizers [13]. Moreover, they are also emerging as a new class of 'green plasticizers' and they are an alternative to existing environmentally friendly materials [10,[17][18][19].…”

Solvent Dependency of Catalyst‐Substrate Aggregation Through π‐π Stacking in Photoredox Catalysis

“…As discussed in previous studies used to determine physical interaction and aggregation, molecular dynamics (MD) and specifically polarizable MD is a more appropriate tool for insight into the modes of interaction between such entities. [19,20] These can be specifically helpful in the instance where the probability of π-π stacking is to be analyzed, [21] or the presence of large aggregates are to be determined. [22,23] For a radical ion photocatalyst to be effective, it needs initially to form an assembly with the substrate that is either favorable (exergonic) or "accessibly endergonic" in solution at room temperature.…”

“…However, the costly nature of QC calculations employing high‐level DFT restricts the observation of systems on a large enough scale to probe the probability of interaction between substrate and catalyst in a dynamic, multicomponent system. As discussed in previous studies used to determine physical interaction and aggregation, molecular dynamics (MD) and specifically polarizable MD is a more appropriate tool for insight into the modes of interaction between such entities [19,20] . These can be specifically helpful in the instance where the probability of π ‐ π stacking is to be analyzed, [21] or the presence of large aggregates are to be determined [22,23] .…”