Progress and Development of Capture for CO2 by Ionic Liquids

Effectiveness of ionic liquid-supported membranes for carbon dioxide capture: a review

The world's population explosion creates a need for natural resources for energy, which will become a significant contributor to global climate change. As we all know, carbon dioxide (CO₂) is one of the most critical elements of the global greenhouse gas effect. CO₂ capture and storage innovations have piqued researchers' attention in recent decades. Compared to other methods, membrane separation has some positive performance in CO₂ capture. CO₂ capture with membrane separation using enhanced ionic liquids (ILs) is described in this review. ILs have made an appearance in CO₂ capture work as the potential additive, and companies and academics have been interested in CO₂ separation for the past two decades. This article comprehensively analyzes the current modern approach in ILs and IL-based membranes for gas separation processes. Based on the latest literature and performance data, this work provides a complete compressive examination of types of ILs and IL-supported membrane performances. ILs for CO₂ capture were also explored, and IL-based membranes for different ILs were also studied. This study emphasizes the supremacy of novel ILs for CO₂ capture in membrane separation.

DFT Study on the Chemical Absorption Mechanism of CO2 in Diamino Protic Ionic Liquids

Diamino protic ionic liquids (DPILs) possess a wide application prospect in the field of acid gas absorption. In this work, two representative DPILs, that is, dimethylethylenediamine 4-fluorophenolate ([DMEDAH][4-F-PhO]) and dimethylethylenediamine acetate ([DMEDAH][OAc]), which had been proved to display favorable CO₂ absorption performance in experiments, were selected. Based on the solvation model, the different mechanisms of CO₂ absorption by [DMEDAH]⁺ cations combined with different anions were investigated using the dispersion-corrected density functional theory method. Above all, the possible active sites of the reaction between DPILs and CO₂ were analyzed by electrostatic potential (ESP) and electronegativity, and the transition states in each path were searched and verified by frequency calculation and intrinsic reaction coordinate calculation. Furthermore, the Gibbs free energy and reaction heat of each path were calculated, and the free energy barrier and enthalpy barrier diagrams were shown. It was found that the absorption path by the anion of [DMEDAH][4-F-PhO] was favorable in kinetics, while the absorption path by the cation was thermodynamically beneficial. In addition, [DMEDAH][OAc] only showed the possibility of cation absorption, and the mechanism of the transfer of active protons to weak acid anions and the formation of acetic acid molecules was more favorable. Moreover, through the structural analysis, bond order and bond energy calculation, ESP analysis of the ion pair absorption configuration, and comparison with the products of CO₂ absorbed by isolated ions, it was found that the interaction between anions/cations and CO₂ could weaken or enhance the interaction between anions and cations in different reaction steps. Hopefully, this study is helpful to understand the absorption mechanism of CO₂ by DPILs and provides a theoretical basis for the R&D of multi-active site functionalized ILs.

Ionic liquids based on bromoxynil for reducing adverse impacts on the environment and human health

Many herbicides exhibit some disadvantages such as high water solubility and volatility after application, which lead to potential threats to the aquatic and atmospheric environment and human health.

Ionic Liquid Induced Band Shift of Titanium Dioxide

Ionic liquids (ILs) have become an established option for the use as electrolytes in dye-sensitized solar cells. In the present study, the adsorption of a multitude of different ILs on a TiO2 surface is studied systematically, focusing on the energetic modifications of the semiconductor. The cation was found to generally cause an energetic downward shift of the TiO2 band levels by accepting electron density from the surface, and the anions were observed to function in the opposite direction, raising the energy levels by donating electron density. Both effects counterbalance each other, leaving the desired outcome dependent on the choice of the specific IL, i.e., the choice of the cation/anion combination. The correlation of the band levels with the properties of the IL was successfully achieved. The dipole moment of the adsorbed ionic liquid species showed little to no correlation with the semiconductor energetics, but the charge transfer calculated by radical Voronoi tessellation revealed a high correlation. The current findings contribute to a deeper understanding of the role of the electrolyte in dye-sensitized solar cells, and ILs in general, and help with choosing and tuning of the electrolyte solutions in existing applications.

Recent advances in carbon dioxide capture, fixation, and activation by using N-heterocyclic carbenes

In the last two decades, CO2 emission has caused a lot of environmental problems. To mitigate the concentration of CO2 in the atmosphere, various strategies have been implemented, one of which is the use of N-heterocyclic carbenes (NHCs) and related complexes to accomplish the capture, fixation, and activation of CO2 effectively. In this review, we summarize CO2 capture, fixation, and activation by utilizing NHCs and related complexes; homogeneous reactions and their reaction mechanisms are discussed. Free NHCs and NHC salts can capture CO2 in both direct and indirect ways to form imidazolium carboxylates, and they can also catalyze the reaction of aromatic aldehydes with CO2 to form carboxylic acids and derivatives. Moreover, associated with transition metals (TMs), NHCs can form NHC-TM complexes to transform CO2 into industrial acid or esters. Non-metal-NHC complexes can also catalyze the reactions of silicon and boron complexes with CO2 . In addition, catalytic cycloaddition of epoxides with CO2 is another effective function of NHC complexes, and NHC ionic liquids perform excellently in this aspect.