Anion-functionalized Ionic Liquids Research Articles

Thermophysical property prediction of anion-functionalized ionic liquids for CO2 capture

We develop a machine learning framework for predicting the density, viscosity, and heat capacity of a family of anion-functionalized ionic liquids for CO2 capture, specifically those with tetraalkylphosphonium cations and aprotic N-heterocyclic anions (AHAs). We screen several feature sets using group contribution-based (GC) descriptors and descriptors extracted from COSMO-RS sigma profiles (SP) to build Support Vector Regression (SVR) and Gradient-Boosted Regression (GBR) machine learning models. Viscosities and densities were modeled based on data sets containing nearly 60 ILs each. The best fit for viscosity used GC-based descriptors and the SVR model, achieving a test set %AARD of 12.5% and R2 of 0.989. Density was modeled using these same descriptors with the SVR model framework and was fitted with a test set %AARD of 1.0%. Heat capacity was fit as a function of molar volume and temperature, a general trend observed for all ILs in a family. Heat capacity predictions could then be made using the density SVR model with a test set accuracy of 3.0 %AARD. With these results, we have developed predictive models which can potentially be used in the design of new advanced ionic liquids for carbon capture.

Insight into the Effect of Physicochemical Properties on CO2 Absorption Behavior of Imidazole Anion-Functionalized Ionic Liquids

Insight into the Effect of Physicochemical Properties on CO2 Absorption Behavior of Imidazole Anion-Functionalized Ionic Liquids

In-situ construction of ionic ultramicroporous metal–organic frameworks for high-efficiency CO2/CH4 separation

The high-efficiency capture of CO2 from biogas by adsorption is highly desirable, which, yet faces the challenges regards of the unsatisfactory adsorption efficiency, selectivity, and regeneration performance. Herein, ionic ultramicroporous metal organic frameworks (IUM-MOFs) with high CO2 affinity are constructed by one-step in-situ coordination strategy and used for CO2/CH4 separation. The phenoxylate anion-functionalized ionic liquid (FIL) serves as competitive ligands in the formation of IUM-MOFs. The oxyl group exhibits high affinity with CO2 as the Lewis basic center, while the rigid counterion occupies the adsorption space of CH4 in the cavities of IUM-MOFs, thus bringing about superior CO2 adsorption capacity of 149 cm3 g−1 (150% higher than that of Cu-BTC) and high IAST predicted selectivity with CH4 of 22 under atmospheric condition. Mechanism analysis demonstrated that the formation of hydrogen bonds between CO2 with coordinated IL and H2O and IL-enhanced polarity of MOFs benefit to the CO2 adsorption. In addition, the IUM-MOFs could be facilely regenerated at 120 °C with favorable recycling stability. This work provides facile strategy for the rational design of IUM-MOFs and lays useful insights for structural tuning to promote their applications.

Efficient catalytic conversion of CO2 to quinazoline-2,4(1H,3H)-diones by a dual-site anion-functionalized ionic liquid: reconsidering the mechanism.

In order to elucidate the reaction mechanism of ionic liquid-catalyzed CO2 with 2-aminobenzonitrile, [P4442]2[Hy] with two N- sites is designed for the efficient preparation of quinazoline-2,4(1H,3H)-diones. The results show that [Hy]2- can activate 2-aminobenzonitrile by hydrogen bonding with -NH2 in addition to activating CO2, and the key intermediate is revealed.

Fluorescent and Colorimetric Ionic Probe Based on Fluorescein for the Rapid and On-Site Detection of Paraquat in Vegetables and the Environment.

Detection of pesticide paraquat (PQ) is of considerable significance to ensure food safety, and its rapid and on-site detection is still a challenge. Aimed at the ion characteristics of PQ, an "enrichment and detection" strategy was proposed to improve the sensitivity through electrostatic attractions, and the ion characteristic of probes was adopted to increase the portability through avoiding aggregation-caused quenching effects in the paper strips. Herein, a novel anion-functionalized ionic liquid (IL) probe with a large conjugated plane and rich π-electrons ([Fluo][P66614]2) was designed as a fluorescent and colorimetric dual-channel probe to sensitively and rapidly detect trace amounts of PQ in vegetables and the environment. The proposed probe exhibited good linearity with a detection limit of 64.0 nM in the PQ concentration range of 0.3-7.0 μM (fluorometry) and 0.1 μM in that of 0.1-8.0 μM (colorimetry), respectively. In addition, it displayed a rapid fluorescence quenching response from green to dark (<5 s) and excellent anti-interference (among 23 other pesticides) due to dual effects of electrostatic attraction and π-π stacking. Most importantly, the lipophilic IL probe could be applied in real vegetables and environmental samples with a satisfying recovery rate of 98-103% and assembled into a handy paper strip that achieved the visual semiquantitative detection of PQ. This ionic probe provides a feasible approach for rapidly and conveniently detecting PQ for ensuring agricultural and food safety and opens a new avenue to detect ion-responsive analytes in real complex samples by an "enrichment and detection" strategy.

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.

Superior selective adsorption of trace CO2 induced by chemical interaction and created ultra-micropores of ionic liquid composites

Effective capture of trace CO2 in atmosphere or confined spaces to ensure human beings safety draw a lot of attention, however, how to simultaneously improve CO2 capacity and selectivity still faces great challenge. Herein, combining porous molecular sieves (SBA-15 and MCM-41) and the anion-functionalized ionic liquid (IL) tetraethylammonium glycinate ([N2222][Gly]), a series of hierarchically porous IL composites with different IL loadings were designed and prepared. Compared with pristine supports, the incorporation of [N2222][Gly] simultaneously improves CO2 capacity and CO2/N2 selectivity by ordersofmagnitude, especially for confined spaces (<5000 ppm) and air (415 ppm). When the IL loading was 60 wt%, novel micropores were created, especially ultra-micropores (<0.65 nm), which are not present in bare supports and other [N2222][Gly]@SBA-15 (15, 30 and 45 wt%). Among them, 60 wt%[N2222][Gly]@SBA-15 showed the highest CO2 uptake of 1.45 and 1.88 mmolCO2/g-adsorbent at 0.0005 and 0.005 bar under 313 K along with recyclability, which are much superior to the state-of-the-art reported values. Moreover, superb ideal CO2/N2 selectivity of 11,545 at 0.005 bar and 288 K was achieved, which was 288 times that of SBA-15. Meanwhile, mixed gas breakthrough experiments demonstrated that 60 wt% [N2222][Gly]@SBA-15 shows outstanding CO2 separation performance under simulative confined spaces and ambient air. The ultra-high CO2 separation performance was attributed to the synergy of chemical interaction between the IL anion and CO2 as well as newly created micro- and ultra-micropores effect. This work provides guidelines for the design of IL composites with ultra-micropores for efficient trace CO2 removal.

Efficient Synthesis of Quinazoline-2,4(1H,3H)-dione via Simultaneous Activated CO2 and 2-Aminobenzonitrile by 1-Methylhydantoin Anion-Functionalized Ionic Liquid through the Multiple-Site Cooperative Interactions

Efficient Synthesis of Quinazoline-2,4(1<i>H</i>,3<i>H</i>)-dione via Simultaneous Activated CO₂ and 2-Aminobenzonitrile by 1-Methylhydantoin Anion-Functionalized Ionic Liquid through the Multiple-Site Cooperative Interactions

Acylamido-based anion-functionalized ionic liquids for efficient synthesis of poly(isosorbide carbonate)

A catalytic system containing an acylamido-based anion was developed for the synthesis of bio-based polycarbonate by efficient activation of monomers.

High performance task-specific ionic liquid in uranium extraction endowed with negatively charged effect

Designing functionalized task-specific ionic liquid is a promising way to alleviate the potential second pollution caused by the usage of tributyl phosphate in PUREX process. In this work, a new anion-functionalized ionic liquid, N,N,N-trimethyltetradecan-1-aminium dibutyl phosphate ([N14111][DBP]), was synthesized and applied in uranium extraction. Thanks to the negatively charged effect, [N14111][DBP] exhibits high efficiency in uranium separation, at optimized condition, the maximum of distribution ratio (concentration of ions in extractant to concentration of ions in aqueous solution) for UO22+ could reach 343.5. What’s more, the selectivity of [N14111][DBP] for UO22+ from transition metal ions was also examined in simulated nuclear industry effluent containing and UO22+ ions were separated and extracted efficiently. The advantage of extraction efficiency and selectivity of [N14111][DBP] compared with DBP highlight the superiority of anion-functionalized extractant.

Highly Efficient and Reversible Absorption and Oxidation of Low-Concentration Nitric Oxide by Functionalized Ionic Liquids

A novel method of using anion-functionalized ionic liquids (ILs) with high NO absorption capacity and reversibility for the capture and in situ oxidation of low-concentration NO was established. For the mixed gas containing 0.25% NO, the accumulation rate of nitric acid in these ILs was significantly higher than that in the conventional ILs; after absorption and oxidation reached equilibrium, the molar ratio of HNO₃ to [P₄₄₄₆][PhSO₃] was 0.86, which was 5 times as high as that of the conventional IL. Therefore, the problems of low efficiency and poor reversibility of traditional ILs in the absorption and oxidation process were solved. Through absorption and oxidation experiments, quantum chemical calculation, NMR, and time-resolved in situ ATR-FTIR spectroscopic investigation, the results demonstrated that such a high accumulation rate of HNO₃ originated from high uptake of NO through multiple-site interaction. Moreover, high reversibility is attributed to low volatility of conjugated acid of anions and decreased basicity of O sites on anions. We believe that such highly efficient and reversible conversion of low-concentration NO to HNO₃ by ILs provides a new strategy for improving atomic economy of fossil fuel combustion, that is, converting post-combustion pollutants to good valuable chemicals.

Anion functionalized ionic liquid from artificial sugar: a sustainable pathway for diverse bis-enol derivatives

An artificial sugar saccharine based anion-functionalized ionic liquid [Bmim]Sac was synthesized and used for new and straightforward strategies for the construction of a diverse range of bis-enols.

Absorption and thermodynamic properties of CO2 by amido-containing anion-functionalized ionic liquids.

In this contribution, two kinds of amido-containing anion-functionalized ionic liquids (ILs) were designed and synthesized, where the anions of these ILs were selected from deprotonated succinimide (H-Suc) and o-phthalimide (Ph-Suc). Then, these functionalized ILs were used to capture CO2. Towards to this end, solubility of CO2 in the ILs was determined at different temperatures and different CO2 partial pressures. Based on these data, chemical equilibrium constants of CO2 with the ILs were derived at different temperatures from the “deactivated IL” model. The other thermodynamic properties such as reaction Gibbs energy, reaction enthalpy, and reaction entropy in the absorption were also calculated from the corresponding equilibrium constant data at different temperatures. It was shown that these anion-functionalized ILs exhibited high CO2 solubility (up to 0.95 mol CO2 mol−1 IL) and low energy desorption, and enthalpy change was the main driving force for CO2 capture by using such ILs as absorbents. In addition, the interactions of CO2 with the ILs were also investigated by 1H NMR, 13C NMR, and FT-IR spectroscopy.

Insights into Carbon Dioxide Electroreduction in Ionic Liquids: Carbon Dioxide Activation and Selectivity Tailored by Ionic Microhabitat.

Electroreduction of carbon dioxide (CO2 ) into high value-added products is a potential solution to a reduction in CO2 levels and its utilization. One major challenge is the lack of an efficient system that can highly selectively reduce CO2 into desirable products with low energy consumption. Ionic liquids (ILs) have been used as electrolytes for the electroreduction of CO2 , and it has been proven that the CO2 -cation complex results in a low-energy pathway. In this work, an ionic microhabitat (IMH) has been built for CO2 electroreduction, and a novel anion-functionalized IL, 1-butyl-3-methylimidazolium 1,2,4triazolide ([Bmim][124Triz]), has been designed as the reaction medium. The results showed that the IMH played a key role in enhancing the performance of CO2 electroreduction, especially in dominating the product selectivity, which is recognized to be a great challenge in an electroreduction process. New insights into the role of the IMH in higher CO2 solubility, bending linear CO2 by forming the [124Triz]-CO2- adduct, and transferring activated CO2 into the cathode surface easily were revealed. The Faradaic efficiency for formic acid is as high as 95.2 %, with a current density reaching 24.5 mA cm-2 . This work provides a promising way for the design of robust and highly efficient ILs for CO2 electroreduction.

Roles of Cation and Anion of Amino Acid Anion-Functionalized Ionic Liquids Immobilized into a Porous Support for CO2 Capture

The impact of cation and anion of amino acid (AA) anion-functionalized ionic liquids (ILs) immobilized into a porous support on the CO2 capture performance was investigated in dry or humidified gas...

Molecular Dynamics Investigation of Efficient SO2 Absorption by Anion-Functionalized Ionic Liquids

Ionic liquids are appropriate candidates for the absorption of acid gases such as SO2. Six anion-functionalized ionic liquids with different basicities have been studied for SO2 absorption capacity by employing quantum chemical calculations and molecular dynamics (MD) simulations. Gas phase quantum calculations unveil that the high uptake of SO2 in these ionic liquids originates from the basicity of the anions and the consequent enhanced anion-SO2 interactions. MD simulations of SO2–IL mixtures reveal the crucial role of both cations and anions in SO2 dissolution. Multiple-site interactions of SO2 with the anions have been identified. The calculated solvation free energy substantiates these observations. The order of computed Henry’s law constant values with change in the anion is in fair agreement with experimentally determined SO2 solubility order.

Peroxotantalate-Based Ionic Liquid Catalyzed Epoxidation of Allylic Alcohols with Hydrogen Peroxide.

The efficient and environmentally benign epoxidation of allylic alcohols has been attained by using new kinds of monomeric peroxotantalate anion-functionalized ionic liquids (ILs=[P4,4,4,n ]3 [Ta(O)3 (η-O2 )], P4,4,4,n =quaternary phosphonium cation, n=4, 8, and 14), which have been developed and their structures determined accordingly. This work revealed the parent anions of the ILs underwent structural transformation in the presence of H2 O2 . The formed active species exhibited excellent catalytic activity, with a turnover frequency for [P4,4,4,4 ]3 [Ta(O)3 (η-O2 )] of up to 285 h-1 , and satisfactory recyclability in the epoxidation of various allylic alcohols under very mild conditions by using only one equivalent of hydrogen peroxide as an oxidant. NMR studies showed the reaction was facilitated through a hydrogen-bonding mechanism, in which the peroxo group (O-O) of the peroxotantalate anion served as the hydrogen-bond acceptor and hydroxyl group in the allylic alcohols served as the hydrogen-bond donor. This work demonstrates that simple monomeric peroxotantalates can catalyze epoxidation of allylic alcohols efficiently.

Reversible CO2 Capture by Conjugated Ionic Liquids through Dynamic Covalent Carbon-Oxygen Bonds.

The strong chemisorption of CO2 is always accompanied by a high absorption enthalpy, and traditional methods to reduce the absorption enthalpy lead to decreased CO2 capacities. Through the introduction of a large π-conjugated structure into the anion, a dual-tuning approach for the improvement of CO2 capture by anion-functionalized ionic liquids (ILs) resulted in a high capacity of up to 0.96 molCO2 mol-1IL and excellent reversibility. The increased capacity and improved desorption were supported by quantum chemical calculations, spectroscopic investigations, and thermogravimetric analysis. The increased capacity may be a result of the strengthened dynamic covalent bonds in these π-electron-conjugated structures through anion aggregation upon the uptake of CO2 , and the improved desorption originates from the charge dispersion of interaction sites through the large π-electron delocalization. These results provide important insights into effective strategies for CO2 capture.

Acylamido-Based Anion-Functionalized Ionic Liquids for Efficient SO2 Capture through Multiple-Site Interactions

Acid gases such as SO2 can be absorbed by ionic liquids (ILs) because of their unique properties. In this work, we developed a new approach for improving SO2 absorption by novel acylamido-based anion-functionalized ILs. Several kinds of such ILs with different structures of acylamido group (anionic acylamide) were designed, prepared, and used for efficient capture of SO2. It was shown that these acylamido-based ILs strongly interacted with SO2, resulting in a very high SO2 capacity up to ∼4.5 mol SO2 per mole of IL. The interactions between acylamido-based ILs and SO2 were investigated by FT-IR, NMR, and quantum chemical calculations. It was found that the dramatic enhancement of SO2 absorption capacity was originated from the multiple-site interactions such as N···S and C═O···S interactions between the anion and SO2. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the SO2-saturated ILs. This novel strategy provides an excellent alternative to current SO2 capture techno...

Designing of anion‐functionalized ionic liquids for efficient capture of SO2 from flue gas

Five kinds of anion‐functionalized ionic liquids (ILs) with different basicity and substituent were selected, prepared and applied in the capture of SO2 from flue gas, where the concentration of SO2 is only 2000 ppm. The effect of the anion on SO2 absorption capacity, desorption residue, and available absorption capacity under 2000 ppm was investigated. The relationship between available absorption capacity and absorption enthalpy was also studied. Through a combination of thermodynamic analysis and quantum calculation, the results indicated that the effect of the cation in the IL on absorption enthalpy was significant. However, the effect of chain length in the cation was weak. Hence, a new IL with low molecular weight, [P4442][Tetz], was further designed and applied for the capture of SO2, which shows the high absorption capacity of 0.18 g SO2 per g IL and excellent reversibility for 2000 ppm SO2. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2028–2034, 2015