Ionic Liquid Solutions Research Articles

Synergistic resource recovery of hydrogen sulfide and carbon dioxide in ionic liquid deep eutectic solution: Construction and development

Synergistic resource recovery of hydrogen sulfide and carbon dioxide in ionic liquid deep eutectic solution: Construction and development

Biobased ionic liquid solutions for an efficient post-combustion CO2 capture system

This study explores the use of ionic liquids (ILs) as a novel and efficient alternative to conventional monoethanolamine (MEA) for CO2 capture. While MEA scrubbing is well-known for carbon sequestration, it faces limitations such as high energy consumption, toxicity, and rapid degradation. In contrast, ILs offer advantages such as non-volatility, stability, and reduced corrosiveness. We focus on a biodegradable IL comprising choline ([Cho]) and proline ([Pro]) amino acids to create an eco-friendly solution. Dimethyl sulfoxide (DMSO) is introduced as a diluent to mitigate viscosity issues during CO2 uptake. Our research measures the thermo-physical properties, including density and viscosity of [Cho][Pro] in DMSO at different concentrations. The addition of DMSO resulted in a viscosity reduction of >97 % at a temperature of 303 K for the three virgin solutions compared to the pure IL. In addition, the CO2 capture performance was evaluated using a system of absorption and desorption reactors. The results show that the 25 % wt [Cho][Pro] solution excels, achieving over 90 % CO2 absorption, 0.66 molCO2/molIL in the first cycle, and demonstrating high reusability and regeneration efficiency over multiple cycles. Comparisons indicate that the IL solution outperforms traditional aqueous MEA solutions. Longer term testing confirms the solution's stability and minimal degradation, achieving a regeneration efficiency of >55 % over 30 cycles, suggesting the potential of [Cho][Pro] for sustainable long-term CO2 capture applications.

A Surface-Active Pt(II) bis-N-Heterocyclic Carbene (NHC) Complex for Interface-Enhanced Supported Ionic Liquid Phase (SILP) Catalysis.

We present the preparation and investigation of a fluorine-free surface-active bis-N-heterocyclic carbene (NHC) platinum(II) complex - trans-[Pt(mPEG3C8Im)2Cl2] - for interface-enhanced supported ionic liquid phase (SILP) catalysis within a group of (mPEGn)-substituted ionic liquids (ILs) ([(mPEGn)2Im][A] ILs). The complex was characterized by means of single-crystal X-ray diffraction (scXRD) analysis and multinuclear (1H, 13C, 195Pt) NMR spectroscopy, indicating the presence of two almost equimolar syn-anti rotamers of the square-planar complex in solution. Angle-resolved X-ray photoelectron spectroscopy (ARXPS) revealed pronounced interface-accumulation of trans-[Pt(mPEG3C8Im)2Cl2] in IL solutions of [(mPEG2)2Im][A] (A- = I- and PF6-).

Theoretical study on the synthesis of HMX via nitrolysis of TAT promoted by ionic liquids

The synthesis of HMX via the TAT method offers an effective strategy. However, the difficulty in synthesizing HMX is mainly limited by the nitration reaction of TAT. Ionic liquids have been shown to facilitate the nitration of energetic materials. Despite these advancements, the theoretical insight for how ionic liquids enhance the selective nitration is still inadequate. This study indicates that the energy barriers for each rate-determining step of the nitration process in ionic liquid solutions are lower compared to those in aqueous solutions, significantly influencing the formation of complexes at different reaction sites of TAT during the initial nitration stages.

Hydrogen radical-boosted electrocatalytic CO2 reduction using Ni-partnered heteroatomic pairs

The electrocatalytic reduction of CO2 to CO is slowed by the energy cost of the hydrogenation step that yields adsorbed *COOH intermediate. Here, we report a hydrogen radical (H•)-transfer mechanism that aids this hydrogenation step, enabled by constructing Ni-partnered hetero-diatomic pairs, and thereby greatly enhancing CO2-to-CO conversion kinetics. The partner metal to the Ni (denoted as M) catalyzes the Volmer step of the water/proton reduction to generate adsorbed *H, turning to H•, which reduces CO2 to carboxyl radicals (•COOH). The Ni partner then subsequently adsorbs the •COOH in an exothermic reaction, negating the usual high energy-penalty for the electrochemical hydrogenation of CO2. Tuning the H adsorption strength of the M site (with Cd, Pt, or Pd) allows for the optimization of H• formation, culminating in a markedly improved CO2 reduction rate toward CO production, offering 97.1% faradaic efficiency (FE) in aqueous electrolyte and up to 100.0% FE in an ionic liquid solution.

Surface-induced nano-generator utilizing a thermo-responsive smart window based on ionic liquid aqueous solution that exhibits lower critical solution temperature type phase separation

We demonstrate a surface-induced nano-generator utilizing a thermo-responsive smart window based on ionic liquid aqueous solution that exhibits lower critical solution temperature (LCST) type phase separation. This smart window was fabricated by filling an aqueous solution of [nBu4P][CF3COO] between the glass substrates coated with two different polymers: a polyimide with an alkyl side chain and an amorphous fluoropolymer. Below the LCST, the transmittance of the smart window was 87 %, nearly identical to that of a glass substrate. In contrast, when heated above the LCST, the [nBu4P][CF3COO] aqueous solution undergoes phase separation, causing the [nBu4P] cations and [CF3COO] anions to adsorb onto the polyimide with the alkyl side chain and the amorphous fluoropolymer facilitated by the surface pinning effect. This adsorption process results in the smart window generating electricity while transitioning to an opaque state. Therefore, the proposed smart window functions as an electricity-generating thermo-responsive device that can switch between transparent and opaque states in response to temperature changes.

Chemical and mechanistic modelling of green solvent extraction of metallic species with 4-acylpyrazolones

Solvent extraction chemistry of metals needs the use of suitable organic ligands like 4-acylpyrazolones to coordinate the studied cation, to make it soluble in an organic phase and then allow its phase transfer from the aqueous phase. The competitive solvent extraction test of almost 25 metal ions by one powerful ligand, i.e. 3-methyl-1-phenyl-4-(4-trifluoromethylbenzoyl)-pyrazol-5-one diluted in one ionic liquid ([C1Cnim+][Tf2N−]) has been conducted to get a snapshot of its efficacy. Effect of diluents on the liquid–liquid extraction of 4f-ions with a series of chelating ligands of 4-acylpyrazolones family (∼5) is presented comparing ionic liquids and typical organic diluents: 14 in number. In addition, the solvent extraction of 12 refractory metals with a series of chelating extractants is investigated in five diluents: four 4-acylpyrazolones with different radicals. The solvent extraction stoichiometry of MoO42− and Zr4+ is studied in detail using molecular and ionic diluent for comparative purposes through slope analysis method. Ethylene glycol is used to develop a non-aqueous process for Gd3+ switchable extraction, i.e. boost of two immiscible organic phases. Furthermore, EPR, NMR, IR and DTA-TG-MS spectroscopies have been used to study the extracted d- and f-species in the obtained organic extracts in ionic liquid solutions.

Binary imidazolium based aqueous ionic liquid droplet on a rough surface: a molecular dynamics study

Ionic liquids (ILs) have garnered immense attention due to their tunable physicochemical properties. In this study, we delve into the wetting behaviour and interfacial properties of aqueous binary IL mixtures containing [EMIM] [BF4] and [HMIM] [BF4] on both smooth and rough graphite surfaces. Employing classical molecular dynamics simulations, we systematically explored the effects of IL concentration and surface morphology on wetting phenomena. To ensure the equilibrium of the systems, we began by calculating the interaction energies between the components. Subsequently, contact angles were computed, shedding light on the wetting characteristics of the aqueous binary IL mixtures. We meticulously examined the density profiles of the IL systems from the substrate to unravel the dominance of one IL over the other, exploiting the hydrophilic nature of [EMIM] [BF4] and the hydrophobic nature of [HMIM] [BF4]. A comprehensive analysis of hydrogen bond distribution allowed us to discern the intricate nature of these aqueous binary IL droplets. We probed the changes in intermolecular forces within the aqueous IL solution by investigating surface tensions. The tunability of these ILs emerges as a significant aspect of our study, paving the way for their tailored application in engineering and scientific domains. Schematic diagram showing the density distribution of hydrophilic and hydrophobic ILs ([EMIM] [BF4] and [HMIM] [BF4]) in water and also the hydrogen bond (HB) distribution of anion ([BF4]−) water inside the droplet on a pillared surface with a surface fraction ( f ) of 0.4 and pillar height of H = 4 .

Choline Oxidase and Choline Ionic Liquids in Biocatalytic Heme Peroxidase Cascades

Choline oxidase from Alcaligenes sp. (ChOx) is used to generate hydrogen peroxide in situ from choline‐based ionic liquids (ILs) to fuel peroxidase‐mediated biocatalysis, while mitigating oxidative degradation of the heme‐dependent enzymes. Horseradish peroxidase (HRP) and chloroperoxidase from Caldariomyces fumago (CPO), in combination with the ChOx, are evaluated in enzymatic cascades for the ability of the biocatalytic systems to withstand elevated concentrations of different choline additives in oxidative and halogenative enzymatic assays. The findings are applied in various synthetic scenarios to produce important oxygen‐ and nitrogen‐containing heterocycles, using choline ILs in a dual‐purpose fashion, as a substrate‐solubilizing component in the reaction medium as well as the source for hydrogen peroxide. The ChOx/HRP couple is used to induce intramolecular cyclizations of hydroxamic acids and hydroxycarbamates in a nitroso‐ene‐type pathway with choline dihydrogen phosphate as IL additive. The ChOx/CPO cascade successfully mediates brominative cyclizations of α‐allenic alcohols, while amphiphilic surfactants are employed to turn the aqueous choline propionate IL media into a colloidal suspension. ChOx/CPO partnering is also evaluated in an oxygenative rearrangement of 1‐furylethanol with choline acetate IL. The results show the wide potential of choline oxidase for hydrogen peroxide‐driven biocatalysis with both aqueous and micellar choline ionic liquid solutions.

Temperature-dependent physicochemical studies of sodium salicylate in aqueous solutions of ionic liquids {[BMIm]Br and [EMIm]Cl}

The current study explores the impact of two different imidazolium based ionic liquids, having diverse side chains and anions: 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) and 1‑butyl‑3-methylimidazolium bromide ([BMIm]Br) on the thermodynamic and transport properties of sodium salicylate. This inquiry examines the sodium salicylate's density, sound velocity, and viscosity within aqueous solutions of these ionic liquids across a temperature range of 283.15 K to 313.15 K at atmospheric pressure. Various parameters, including apparent molar volume (Vϕ), limiting apparent molar volume (Voϕ), transfer volume (ΔtrV∘ϕ), limiting apparent molar expansibility (E∘∅), Hepler's constant, apparent molar isentropic compression (Kϕ,s), limiting apparent molar isentropic compression (K∘ϕ,s), transfer parameter of isentropic compression (ΔtrK∘ϕ,S), and viscosity B-coefficient, were computed from experimental values. Additionally, we have analyzed the trends in computed parameters, considering the interactions between `solute and solvent along with solute-solute interactions in the systems under investigation. Our results suggest a predominance of hydrophilic-hydrophilic and ion-hydrophilic interactions within studied systems. The observed magnitudes of these parameters affirm a stronger interaction between sodium salicylate and [BMIm]Br in comparison to those with [EMIm]Cl.

Superparamagnetic composites of lignin regenerated from ionic liquid solutions for the efficient and selective removal of cationic dyes

Magnetic lignin nanoparticles (MLNs) were prepared by inducing their self-assembly through lignin regeneration in the [N-methyl-2-pyrrolidone][C1–C4 carboxylic acid] ionic liquids ([NMP]ILs), which are low-cost protic ionic liquid. [NMP]ILs are self-assembling solvent that can enhance the adsorption capacity of MLNs to a greater degree than tetrahydrofuran or H2O. Additionally, the anion types of [NMP]IL greatly influence the physiochemical properties of MLNs. The MLNs prepared through self-assembly with [NMP][formate] (MLN/[NMP][For]) exhibited a higher maximum adsorption capacity (134.53 mg/g) than the [NMP]ILs of C2–C4 carboxylate anions. MLN/[NMP][For] demonstrated stable adsorption within a pH range of 6–10 or at high salt concentrations (0.01–0.5 mol/L), retaining over 80 % of its regeneration efficiency after 5 cycles. In addition, MLN/[NMP][For] selectively removed cationic dyes in mixed binary anionic–cationic dye solutions. This work demonstrated the feasibility of preparing magnetic biosorbents with good selectivity and stability though regeneration and by adjusting the anions of ionic liquids.

Cytotoxicity and cell membrane interactions of choline-based ionic liquids: Comparing amino acids, acetate, and geranate anions

Ionic liquids (ILs) have found diverse applications in research and industry. Biocompatible ILs, a subset considered less toxic than traditional ILs, have expanded their applications into biomedical fields. However, there is limited understanding of the toxicity profiles, safe concentrations, and underlying factors driving their toxicity. In this study, we investigated the cytotoxicity of 13 choline-based ILs using four different cell lines: Human dermal fibroblasts (HDF), epidermoid carcinoma cells (A431), cervical cancer cells (HeLa), and gastric cancer cells (AGS). Additionally, we explored the haemolytic activity of these ILs. Our findings showed that the cytotoxic and haemolytic activities of ILs can be attributed to the hydrophobicity of the anions and the pH of the IL solutions. Furthermore, utilising quartz crystal microbalance with dissipation (QCM-D), we delved into the interaction of selected ILs, including choline acetate [Cho][Ac] and choline geranate [Cho][Ge], with model cell membranes composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). The QCM-D data showed that ILs with higher toxicities exhibited more pronounced interactions with membranes. Increased variations in frequency and dissipation reflected substantial changes in membrane fluidity and mass following the addition of the more toxic ILs. Furthermore, total internal reflection fluorescence microscopy study revealed that [Cho][Ac] could cause lipid rearrangements and pore formation in the membrane, while [Cho][Ge] disrupted the bilayer packing. This study advances our understanding of the cellular toxicities associated with choline-based ILs and provides valuable insights into their mechanisms of action concerning IL-membrane interactions. These findings have significant implications for the safe and informed utilisation of biocompatible ILs in the realm of drug delivery and biotechnology.

2′-Deoxyribo-oligonucleotides duplexes and G-quadruplexes structures and thermal stability in 1‑butyl‑1-methylpiperidinium and 1-octyl-3-methylimidazolium bromide ionic liquid solutions

Conformation and thermal stability of duplexes made of various ratio of purine and pyrimidine, but also of two G-quadruplexes, were evaluated in two different ionic liquids, aliphatic 1‑butyl‑1-methylpiperidinium bromide and 1-octyl-3-methylimidazolium bromide with an aromatic moiety, by means of UV-spectroscopy and circular dichroism. It appeared that no conformational change occurred within all structures studied whatever the medium was, only thermal stabilities were affected.

Competitive Effects of Anions on Protein Solvation by Aqueous Ionic Liquids.

The present study utilizes molecular dynamics simulations to examine how different anions compete for protein solvation in aqueous solutions of ionic liquids (ILs). Ubiquitin is used as model protein and studied in IL mixtures sharing the same cation, 1-ethyl-3-methylimidazolium (EMIM), and two different anions in the same solution, from combinations of dicyanamide (DCA), chloride (Cl), nitrate (NO3), and tetrafluoroborate (BF4). Our findings reveal that specific interactions between anions and the protein are paramount in IL solvation, but that combinations of anions are not additive. For example, DCA exhibits a remarkable ability to form hydrogen bonds with the protein, resulting in a significantly stronger preferential binding to the protein than other anions. However, the combination of DCA with NO3, which also forms hydrogen bonds with the protein, results in a smaller preferential solvation of the protein than the combination of DCA with chloride ions, which are weaker binders. Thus, combining anions with varying affinities for the protein surface modulates the overall ion accumulation through nonadditive mechanisms, highlighting the importance of the understanding of competition for specific interaction sites, cooperative binding, bulk-solution affinity, and overall charge compensations, on the overall solvation capacity of the solution. Such knowledge may allow for the design of novel IL-based processes in biotechnology and material science, where fine-tuning protein solvation is crucial for optimizing performance and functionality.

Osmotic absorption behaviors of imidazolium ILs in digestive system and their effective removal way

Considering the controversial safety and risk solutions of ionic liquids (ILs), more essential basic researches are required as their applied fields become broader and applied scale grows larger. Under this background, the permeation behaviors of six common imidazole ILs on porcine gastric and enteric membranes together with the feasibility of their removal by adsorption with montmorillonite were investigated in vitro. Through the single-factor investigation of different cations, anions and ionic liquid concentrations, the current results show that the IL of 1-ethyl-3-methylimidazolium bromide ([Emim]Br) has the strongest permeation capacity on the gastric membrane during the tests. The cumulative permeation amount of Qn can reach 0.72 mg/cm2, and the cumulative permeation percentage alsoreaches 95.77 %; the whole permeation process conforms to the Hixcon-Crowell model. As comparison, the maximum cumulative penetration percentage of [Emim]Br on enteric member was determined as 89.11 %, and related models was also compared. In order to remove the potential IL in digestive tract, montmorillonite was screened out from those popularily used antidotes in clinic and the adsorption of [Emim]Br in gastric fluid by montmorillonite has been proved more consistent with the second-order kinetics and Langmuir model. The results of molecular simulation, infrared spectrum (IR), X-ray diffraction (XRD) and thermogravimetric (TG) characterization exhibit that [Emim]Br has been successfully adsorbed into the interlayer of montmorillonite. As a whole, the study provided a scientific and effective way to diminish the hidden danger of ionic liquid entering the blood through the digestive system.

Controlled Interlayer Binding and Healing Improve the Transverse Properties of Upcycled Disposable Waste Wood.

Recovery and reuse of bulk waste wood are particularly challenging because of usage defects and contaminations. Here, we present a robust and efficient strategy for regenerating used wood veneers into high-performance structural materials through micro/nano interface manipulation. Our approach involves using cellulose-based interlayers to bind together two waste wood plates without an external adhesive by partially dissolving and regenerating the interlayer using a solution of ionic liquids and dimethyl sulfoxide. The mechanical properties of the regenerated wood exceed that of natural wood, displaying over a 16 and 20 times increase in transverse tensile strength and modulus, respectively, and 4-6 times improvement in longitudinal tensile strength and modulus. Nanoscale mechanical analyses show that the improvement is possible as a result of several factors, including the robust network structure of the interlayer, the good adhesion at the wood-interlayer interface, the compacted wood structure, and the low stiffness and deformation gradients between the interlayer and the wood structure. The interlayers can be created from waste papers and wood particles by taking advantage of the nanofibrillar structure of cellulose.

Exploration of diverse interactions of nonionic poly(vinylpyrrolidone) (PVP) and anionic sodium carboxymethylcellulose (NaCMC) polymers in aqueous imidazolium-based surface active ionic liquid solutions

The binding interactions in complex formation between surface active ionic liquids (SAILs) and polymers (nonionic or anionic) are gaining attention because of their potential applications in novel materials. Therefore, the use of a variety of measurements is required for a better understanding of the interactions involved in polymer/SAIL formation. Here, we have investigated the interactions of nonionic poly(vinylpyrrolidone) (PVP) and anionic sodium carboxymethylcellulose (NaCMC) polymers with SAIL 1-tetradecyl-3-methylimidazolium chloride [C14mim][Cl] in aqueous solution using different measurements such as conductivity, surface tension, fluorescence spectroscopy, dynamic light scattering (DLS) and rheometric measurements. The surface tension, conductivity and fluorescence profiles for SAIL-NaCMC systems provide distinct breakpoints that correspond to four different aggregation states: the concentration at which SAIL monomers begin to attach to the polymer chain (C1), the critical aggregation concentration C2 (cac), the saturation concentration (CS) and the critical micelle concentration (cmc). In the case of SAIL-PVP systems, the surface tension and fluorescence profiles confer three transition states: C2 (cac), CS and cmc and only two transition states have been observed in conductivity curves. The cooperative binding of SAIL to the NaCMC/PVP chain at the solution interface was analyzed by calculating various thermodynamic and interfacial parameters. Strong complexation was observed between NaCMC-SAIL molecules compared to PVP-SAIL systems at the air-solution surface. This is due to the non-ionic character of the PVP chain, which shows weak interactions with SAIL in comparison to NaCMC. Furthermore, DLS and fluorescence measurements were used to investigate the interactions between SAIL and polymers.

Studies on wetting behaviour of pure and aqueous protic ionic liquids (PIL) solutions on different surfaces: ILphobicity to ILphilicity

In this study, the wetting behaviour of pure protic ionic liquids (PILs) and their mixture with water was studied at ambient conditions. Ethanolammonium acetate [EAAc], ethanolammonium butyrate [EABu], and ethanolammonium hexanoate [EAHx] were used as PILs for the wetting studies on various surfaces. The contact angle and wetting area of pure and mixed PIL solutions were determined on superhydrophobic, hydrophilic, and total wetting surfaces. Smaller alkyl chain PIL, ethanolammonium acetate (EAAc) displayed the highest contact angle (CA) of 141° on superhydrophobic surfaces. On hydrophilic polycarbonate (PC), shorter anionic chain PILs demonstrated CA < 90°, showing the ILphilic behaviour, and the variation of CA was PIL anionic chain length dependent. Total wetting glass exhibited the lowest CA for [EAAc], which increased with the PIL anionic chain. A binary mixture of PIL with water demonstrated unique wetting behaviour on the total wetting surface. The aqueous drops of EAHx exhibited a dynamic contact line on the glass surface, showing the greatest expansion in wetting area compared to drops of aqueous EAAc or aqueous EABu. This occurrence could be ascribed to the substantial decrease in water surface tension induced by the hydrophobic hexanoate anion, potentially leading to improved spreading characteristics.

On the Moisture Absorption Capability of Ionic Liquids.

Due to their many attractive physicochemical properties, ionic liquids (ILs) have received extensive attention with numerous applications proposed in various fields of science and technology. Despite this, the molecular origins of many of their properties, such as the moisture absorption capability, are still not well understood. For insight into this, we systematically synthesized 24 types of ILs by the combination of the dimethyl phosphate anion with various types of alkyl group-substituted cyclic cations─imidazolium, pyrazolium, 1,2,3-triazolium, and 1,2,4-triazolium cations─and performed a detailed analysis of the dehumidification properties of these ILs and their aqueous solutions. It was found that these IL systems have a high dehumidification capability (DC). Among the monocationic ILs, the best performance was obtained with 1-cyclohexylmethyl-4-methyl-1,2,4-triazolium dimethyl phosphate, whose DC (per mol) value is 14 times higher than that of popular solid desiccants like CaCl2 and silica gel. Dicationic ILs, such as 1,1'-(propane-1,3-diyl)bis(4-methyl-1,2,4-triazolium) bis(dimethyl phosphate), showed an even better moisture absorption, with a DC (per mol) value about 20 times higher than that of CaCl2. Small- and wide-angle X-ray scattering measurements of eight types of 1,2,4-triazolium dimethyl phosphate ILs were performed and revealed that the majority of these ILs form nanostructures. Such nanostructures, which vary with the identity of the IL and the water content, fall into three main categories: bicontinuous microemulsions, hexagonal cylinders, and micelle-like structures. Water in the solutions exists primarily in polar regions in the nanostructures; these spaces function as water pockets at relatively low water concentrations. Since the structure and stability of the aggregated forms of the ILs are mainly governed by the interactions of nonpolar groups, the alkyl side chains of the cations play an important role in the DC and temperature-dependent equilibrium water vapor pressure of the IL solutions. Our experimental findings and molecular dynamics simulation results shed light on the moisture absorption mechanism of the IL aqueous solutions from a molecular perspective.

Insight into the Inflection Point of Surface Tension in Aqueous Solution of Imidazolium-Based Ionic Liquids

Insight into the Inflection Point of Surface Tension in Aqueous Solution of Imidazolium-Based Ionic Liquids