Computer-Assisted Design of Imidazolate-Based Ionic Liquids for Improving Sulfur Dioxide Capture, Carbon Dioxide Capture, and Sulfur Dioxide/Carbon Dioxide Selectivity

Carboxylative cyclization of atmospheric CO2 with alkynol catalyzed by a 1-methylhydantoin anion-functionalized ionic liquid via chelative interactions

Metal- and solvent-free carboxylative cyclization of atmospheric CO2 with alkynol can be achieved using a 1-methylhydantoin anion-functionalized ionic liquid. 1H NMR, in situ FT-IR and DFT calculations indicate that the 1-methylhydantoin anion acts as a "pincer ligand" to form chelative interactions with the hydroxyl group, thereby effectively activating the alkynol.

Reactive capture and electrochemical conversion of CO2 with ionic liquids and deep eutectic solvents

Ionic liquids (ILs) and deep eutectic solvents (DESs) have tremendous potential for reactive capture and conversion (RCC) of CO2 due to their wide electrochemical stability window, low volatility, and high CO2 solubility. There is environmental and economic interest in the direct utilization of the captured CO2 using electrified and modular processes that forgo the thermal- or pressure-swing regeneration steps to concentrate CO2, eliminating the need to compress, transport, or store the gas. The conventional electrochemical conversion of CO2 with aqueous electrolytes presents limited CO2 solubility and high energy requirement to achieve industrially relevant products. Additionally, aqueous systems have competitive hydrogen evolution. In the past decade, there has been significant progress toward the design of ILs and DESs, and their composites to separate CO2 from dilute streams. In parallel, but not necessarily in synergy, there have been studies focused on a few select ILs and DESs for electrochemical reduction of CO2, often diluting them with aqueous or non-aqueous solvents. The resulting electrode-electrolyte interfaces present a complex speciation for RCC. In this review, we describe how the ILs and DESs are tuned for RCC and specifically address the CO2 chemisorption and electroreduction mechanisms. Critical bulk and interfacial properties of ILs and DESs are discussed in the context of RCC, and the potential of these electrolytes are presented through a techno-economic evaluation.

CO2 capture by imidazolium-based deep eutectic solvents: the effect of steric hindrance of N-heterocyclic carbenes

CO2 capture by deep eutectic solvents (DESs) formed between 1,3-bis(isopropyl)imidazolium 1,2,4-triazolide ([IiPim][Triz]) and ethylene glycol (EG) is investigated in this study. [IiPim][Triz]-EG DESs exhibit a capacity of ∼1.0 mol CO2 per mol DES at 1.0 atm and 25 °C. Surprisingly, mechanistic results disclose that CO2 reacts with EG but does not bind with the C-2 site of the [IiPim]+ cation, which may be due to the high steric hindrance of the C-2 site of the N-heterocyclic carbene IiPim present in [IiPim][Triz]-EG DESs.

Unveiling protic amino acid ionic liquids for the efficient capture of carbon dioxide

A series of novel protic amino acid ionic liquids (PAAILs) are designed and synthesized for the first time through acid-base neutralization and an ion exchange reaction. Among the synthesised PAAILs, the [DBNH][Maba] PAAIL has the largest CO2 absorption capacity of 0.78 mol mol-1 (0.142 g g-1) at 313.2 K. The PAAILs are found to be efficient, reversible, and selective CO2 absorbents.

Tuning Ionic Liquid-Based Catalysts for CO2 Conversion into Quinazoline-2,4(1H,3H)-diones

Carbon capture and storage (CCS) and carbon capture and utilization (CCU) are two kinds of strategies to reduce the CO2 concentration in the atmosphere, which is emitted from the burning of fossil fuels and leads to the greenhouse effect. With the unique properties of ionic liquids (ILs), such as low vapor pressures, tunable structures, high solubilities, and high thermal and chemical stabilities, they could be used as solvents and catalysts for CO2 capture and conversion into value-added chemicals. In this critical review, we mainly focus our attention on the tuning IL-based catalysts for CO2 conversion into quinazoline-2,4(1H,3H)-diones from o-aminobenzonitriles during this decade (2012~2022). Due to the importance of basicity and nucleophilicity of catalysts, kinds of ILs with basic anions such as [OH], carboxylates, aprotic heterocyclic anions, etc., for conversion CO2 and o-aminobenzonitriles into quinazoline-2,4(1H,3H)-diones via different catalytic mechanisms, including amino preferential activation, CO2 preferential activation, and simultaneous amino and CO2 activation, are investigated systematically. Finally, future directions and prospects for CO2 conversion by IL-based catalysts are outlined. This review is benefit for academic researchers to obtain an overall understanding of the synthesis of quinazoline-2,4(1H,3H)-diones from CO2 and o-aminobenzonitriles by IL-based catalysts. This work will also open a door to develop novel IL-based catalysts for the conversion of other acid gases such as SO2 and H2S.

Tuning Functionalized Ionic Liquids for CO2 Capture

The increasing concentration of CO₂ in the atmosphere is related to global climate change. Carbon capture, utilization, and storage (CCUS) is an important technology to reduce CO₂ emissions and to deal with global climate change. The development of new materials and technologies for efficient CO₂ capture has received increasing attention among global researchers. Ionic liquids (ILs), especially functionalized ILs, with such unique properties as almost no vapor pressure, thermal- and chemical-stability, non-flammability, and tunable properties, have been used in CCUS with great interest. This paper focuses on the development of functionalized ILs for CO₂ capture in the past decade (2012~2022). Functionalized ILs, or task-specific ILs, are ILs with active sites on cations or/and anions. The main contents include three parts: cation-functionalized ILs, anion-functionalized ILs, and cation-anion dual-functionalized ILs for CO₂ capture. In addition, classification, structures, and synthesis of functionalized ILs are also summarized. Finally, future directions, concerns, and prospects for functionalized ILs in CCUS are discussed. This review is beneficial for researchers to obtain an overall understanding of CO₂-philic ILs. This work will open a door to develop novel IL-based solvents and materials for the capture and separation of other gases, such as SO₂, H₂S, NOx, NH₃, and so on.

Capture of Acidic Gases from Flue Gas by Deep Eutectic Solvents

Up to now, many kinds of deep eutectic solvents (DESs) were investigated for the capture of acidic gases from flue gases. In this review, non-functionalized and functionalized DESs, including binary and ternary DESs, for SO2, CO2 and NO capture, are summarized based on the mechanism of absorption, physical interaction or chemical reaction. New strategies for improving the absorption capacity are introduced in this review. For example, a third component can be introduced to form a ternary DES to suppress the increase in viscosity and improve the CO2 absorption capacity. DESs, synthesized with halogen salt hydrogen bond acceptors (HBAs) and functionalized hydrogen bond donors (HBDs), can be used for the absorption of SO2 and NO with high absorption capacities and low viscosities after absorption, due to physicochemical interaction between gases and DESs. Emphasis is given to introducing the absorption capacities of acidic gases in these DESs, the mechanism of the absorption, and the ways to enhance the absorption capacity.

Significantly promoted SO2 uptake by the mixture of N-methylated ethylene imine polymer and 1-ethyl-3-methylimidazolium tetrazolate

A novel class of hybrid solvents (mEIP:Tetz) comprising of N-methylated ethylene imine polymer (mEIP) and 1-ethyl-3-methylimidazolium tetrazolate ([Emim][Tetz]) were developed for the highly efficient and reversible capture of SO₂. The synergistic interactions rather than simple mixing between mEIP and [Emim][Tetz] were confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and density functional theory (DFT) calculations. Besides, it was experimentally demonstrated that mEIP:Tetz mixtures exhibited improved kinetics for SO₂ absorption, and the production of viscous solids were completely eliminated, compared with using mEIP alone. More significantly, an exceedingly high solubility of 0.308 g SO₂·g^-1 absorbent in 2mEIP:8Tetz was received for trapping SO₂ from simulated flue gas containing 2000 ppm SO₂, which was much higher than most of the results reported in previous literatures under the same conditions. Finally, the absorption and desorption mechanisms were proposed according to the results of FTIR and ¹H NMR analysis.

SO2 absorption in pure ionic liquids: Solubility and functionalization

The SO₂ solubility in ionic liquids and absorption mechanisms with different functionalities, including ether, halide, carboxylate, dicarboxylate, thiocynate, phenol, amino, azole groups, etc., are presented in this review. Strategies of improving SO₂ capture with low binding energy and the separation performance from CO₂ are also concluded. Generally, moderate basicity is favourable for enhancing SO₂ capacity and the water (below 6 wt%) effect on absorption is indefinite but generally slight. Introducing electron-withdrawing substituents such as nitrile, halogen, aldehyde and carboxylic groups are proposed to decrease the chemical absorption enthalpy between ionic liquid and SO₂ in order to reduce regeneration power consumption. Although it is promising, the absorption enthalpy is still much higher than the physisorption performance especially of the ether-functionalized ones. The biocompatible choline-based, betaine-based, and amino acid ionic liquids have clear trends to be applied in SO₂ capture due to their biodegradability, nontoxicity and easy accessibility. Generally, comparing to the traditional solvents, ionic liquids have made great improvement in SO₂ capacity, however, the high viscosity and desorption energy are two main obstacles for SO₂ absorption and separation. Molecular simulations have been applied to reveal the absorption regimes involving the roles of basic functionalities and physical interactions especially the hydrogen bonds, which could be referred for structure designing of the available ionic liquids with readily fluid characteristics and absorption ability.

Exploration of tetra-branched multiple-site SO2 capture materials

Efficient exploration of the configuration space of the reaction complexes consisting of multi-branched structures and SO₂ molecules.

Efficient and reversible absorption of NH3 by functional azole–glycerol deep eutectic solvents

The hydrogen bond donor (HBD) of glycerol and hydrogen bond acceptor (HBA) selected from azole compounds were paired to construct functional deep eutectic solvents (DESs) as NH₃ absorbents.

Designing tri-branched multiple-site SO2 capture materials

Tri-branched species with multiple isolated reactive sites are proposed for high and uniform SO₂ capture.