Acidic Ionic Liquid Research Articles

Introduction of amino acid ionic liquid into the gelatin matrix enhances the performance of immobilized laccase in degrading 2,4-dichlorophenol

The utilization of immobilized laccase to degrade and remove phenolic pollutants in water has promising application prospects. However, maintaining the activity and stability of the immobilized laccase remains a significant challenge. In this work, an amino acid-based ionic liquid (IL) modified magnetic composite material (IL-Magnetic gelatin) was prepared as a support for laccase immobilization. We conducted a detailed characterization of the nanocomposite and it exhibited excellent magnetic responses and dispersion. The catalytic performance of the immobilized enzyme was also investigated. Compared to free laccase, the immobilized laccase (Lac-IL-Magnetic gelatin) exhibited higher catalytic activity and better thermal stability. The various interactions (hydrogen bonds, ionic interaction) between enzyme molecule and ionic liquid can cause conformational rearrangement of laccase. Lac-IL-Magnetic could degrade 98.6 % of 2,4-dichlorophenol (2,4-DCP) within 20 h and maintained 55.2 % activity after 10 cycles. Moreover, the biocatalyst is easy to recycle using magnet. The results indicated that Lac-IL-Magnetic gelatin holds significant potential for the degradation of phenolic substances in environmental wastewater.

A novel MOF-808 derived material for oxidative desulfurization: the synergistic effect of hydrophobicity and electron transfer.

A functionalized modified metal-organic framework material, T-MOF-808, was synthesized through hydrophobic modification with tetraethyl orthosilicate (TEOS) and chlorotrimethylsilane (TMCS). Then a supported oxidative desulfurization catalyst, [C12Py]3(NH4)3Mo7O24/T-MOF-808(s), was prepared by using a heteropoly acid ionic liquid as the active component. The prepared samples were characterized using FT-IR, XRD, SEM, TEM, XPS, etc. [C12Py]3(NH4)3Mo7O24/T-MOF-808(s) was used in the oxidative desulfurization of dibenzothiophene (DBT). At the same time, the effects of different loadings of the active component, oxygen sulfur ratios, reaction temperatures, and reaction time were also investigated. [C12Py]3(NH4)3Mo7O24/T-MOF-808-15%(s) could oxidize 100% of DBT in 40 min at 60 °C. Significantly, the catalyst exhibited no discernible decline in catalytic activity after 14 runs. In addition, the efficiency of sulfur removal was 85.76% in actual diesel oil. It was found that the cooperative impact of hydrophobic modification and electron transfer makes an important contribution to the high activity. The hydrophobic modification provides a novel approach for using MOF materials in the oxidative desulfurization process.

Graph transformer based transfer learning for aqueous pKa prediction of organic small molecules

The acid-base dissociation constant (pKa) is an essential physicochemical parameter that indicates the extent of proton dissociation. However, accurately predicting pKa values is still challenging due to limited data availability for organic small molecules in aqueous solutions. In this work, we propose an open-source pKa prediction tool based on Graph Transformer, which combines the graph neural network and transformer to take both local and global information into account. To address the limitation of data scarcity, the experimental dataset is expanded, while transfer learning is employed by pre-training on the ChEMBL (computational) dataset and fine-tuning on the experimental dataset. The performance and generalization of the obtained models are comprehensively evaluated on both internal and external test sets. Additionally, two exemplary applications, namely the screening of tertiary amines for CO2 absorption and acidic ionic liquids for reactive extraction, are investigated to validate the reliability of our tool. The results show that our model can effectively guide the identification of promising candidates for the target applications by achieving accurate pKa predictions.

Acid-base neutralization strategy for immobilization amino acid ionic liquid within sulfonic acid-based COF as a switch for selective conversion of epoxides

Covalent organic frameworks (COFs) and ionic liquids (ILs) as raw materials exhibit effective catalytic performance and adsorption capabilities in the reaction of epoxides and atmospheric CO2, respectively. Nonetheless, bonding modes between ILs and COFs have restricted their utility, thereby constraining the in-depth study of synergistic catalytic mechanisms over these composite catalysts. Herein, a heterogeneous composite ([DBUH]2Cys@COF-X) were successfully prepared by the facile acid-base neutralization method, incorporating varying amounts of amino acid ILs ([DBUH]2Cys) into the pore channels of sulfonic acid-based COF (TpPa-SO3H). [DBUH]2Cys@COF-3 efficiently catalyzed epichlorohydrin with a yield of 96.38 % without any solvent or co-catalyst under atmospheric CO2. Notably, larger sterically hindered epoxides were selectively blocked on the surface of [DBUH]2Cys@COF-3, enabling [DBUH]2Cys@COF-3 to act as a gatekeeper for selectively catalyzing small sterically hindered epoxides due to [DBUH]2Cys was distributed within the pore channels of [DBUH]2Cys@COF-3. Through DFT calculations, comprehensive understanding of the synergistic activation conferred of -COO- and [DBUH]+ towards CO2 and epoxides in [DBUH]2Cys@COF-3 and the ring-opening mechanism was clarified. This work presents a fresh outlook on the catalyst design by the facile acid-base neutralization method for efficiently catalyzing small-hindered epoxides under atmospheric CO2.

New halloysite-supported bio-based acidic ionic liquid as an efficient catalyst for conversion of fructose to 5-hydroxymethylfurfural: A combined experimental and computational studies

In an effort to design a bio-based catalyst with enough acidic strength to promote the conversion of fructose to 5-hydroxymethylfurfural, a series of halloysite clay-supported acidic ionic liquids were considered as potential candidates. The catalysts could be synthesized from reaction of Cl-functionalized halloysite with histidine, histamine, adenine and tryptophan, followed by treatment with chlorosulfuric acid. Predictive computational studies were performed and approved the superior activity of the histidine-based catalyst. In addition, the computational studies aimed to identify the optimal catalyst using Density Functional Theory (DFT) calculations and other characterization techniques, particularly non covalent interactions plots. Aknowledged by computational results, histidine based catalyst was prepared, characterized and its catalytic activity and recyclability were appraised for the synthesis of 5-hydroxymethylfurfural from fructose as a bio-based starting material. The reaction conditions were optimized and it was revealed that using 30 wt% catalyst, the desired product could be achieved at 100 °C within 1 h. Notably, the catalyst exhibited high recyclability and efficiently promoted the reaction of other mono-saccharides as well.

Tandem catalytic conversion of glucose and cellobiose to 5-ethoxymethylfurfural with record yields

The conversion of biomass-derived carbohydrates to 5-ethoxymethylfurfural (EMF) is a fascinating reaction with 100% carbon atom utilization. Although effective conversion of 5-hydroxymethylfurfural (HMF) and fructose to EMF have been achieved, the direct conversion of glucose only gave low EMF yields. Herein, we reveal that the combinations of common Lewis acid with Brønsted acid in ethanol universally catalyze rapid etherification of glucose to intractable ethyl glucoside (EGL), as impedes the further conversion toward the desired products. The synergy of large-pore tin phosphate (SnPO) bearing strong Lewis acidic sites with acidic ionic liquid 1-(4-sulfobutyl)-3-methylimidazolium chloride (BSO3HMIMCl) enable tandem catalytic conversion of glucose, cellobiose and starch to EMF with record yields (61.7%, 61.8% and 55.7%, respectively), far exceeding previous reports. This transformation probably occurs via multiple parallel pathways, where water molecules generated by dehydration cooperate with acid and Cl- to hydrolyze EGL back to glucose, thus forming a positive feedback on EMF production.

Tribological and Anticorrosion Properties of N-Heterocyclic-Organophosphonic Acid Ionic Liquids as Water-Based Lubricant Additives

Four ionic liquids (ILs) were synthesized by a simple neutralization reaction using 1,8-diazabicyclo[5.4.0]undecane-7-ene as the cation and organophosphonic acids with different carbon chain lengths as the anion. The obtained ILs had an excellent water-soluble property and the tribological performance was studied by a four-ball friction tester. The results showed that the longer carbon chains, the better tribological properties of the ILs. Compared with the blank, only 0.05 wt% of ILs addition resulted in the decrease of friction coefficient and wear volume about 30% and 60%, respectively. The adsorption state of the ionic liquid on the steel surface was also investigated by molecular dynamics simulation. It is believed that the good tribological performance and corrosion inhibition was attributed to the effective physical adsorption due to the polarity of the organophosphonate, which can form an effective adsorption film and prevent the steel surface from corrosion.

Efficacy of tethered Pyridinium-Based ionic liquid immobilized on Zn-MOF-NH2 for effectively converting CO2 into cyclic carbonates under Co-Catalyst-free and solvent-free conditions

A new bifunctional heterogeneous catalyst system was developed by immobilization of pyridinium-based ionic liquid on Zn-MOF-NH2 to produce an IL-supported Zn-MOF-NH2 catalyst. The dual-functional one-component system, including both Lewis acid sites and IL functional sites, showed high catalytic activity for the CO2-epoxide cycloaddition reactions under mild solvent-free conditions. Different techniques such as FE-SEM, EDX, FT-IR, XRD, and BET were applied to characterize of the as-prepared catalyst. This efficient low-leaching catalyst system is separated by centrifugation and can be reused successfully for four successive cycles without altering the catalytic activity in CO2 epoxidation to cyclic carbonates. Due to the wide variety seen in both metal–organic frameworks (MOFs) and ionic liquids (ILs), we believe that this research represents a significant step forward in the potential applications of synthetic modification methods within MOFs.

Intensification Mechanism of Acidic Imidazole-Based Ionic Liquids on the Synthesis of 1,3,5-Trioxane Catalyzed by Sulfuric Acid

Intensification Mechanism of Acidic Imidazole-Based Ionic Liquids on the Synthesis of 1,3,5-Trioxane Catalyzed by Sulfuric Acid

Theoretical study on the energy storage performance of Electrical double layer supercapacitors with choline amino acid ionic liquids electrolyte

Choline amino acid ionic liquids have attracted much attention in recent years due to their simple extraction process, rich sources, and easy degradation. Due to the high viscosity of such ionic liquids, the addition of organic solvents can adjust the transport performance of ionic liquids. Here, we explore the effects of different solvents (methanol, ethanol) and different temperatures on the diffusion properties and conductivity of ionic liquids through molecular dynamics simulations. The results showed that with the increase of temperature, the conductivity linearly increased. The addition of organic solvents can improve the conductivity of ionic liquids, and the addition of methanol solvent has a higher compatibility with choline amino acid ionic liquids. The conductivity after mixing methanol and choline glycine in a certain proportion is 5 times higher than before. In addition, this article investigated the performance of choline glycine ionic liquid electrolytes in Electrical Double Layers (EDLs) near planar graphene electrodes. The results indicate that similar double layer structures and double layer capacitors can be observed regardless of whether solvents are added.

Strategic design of magnetic ionic covalent organic frameworks incorporating amino acid ionic liquids for enhanced selectivity adsorption of benzimidazoles

Advancing the frontier of material design, our innovative magnetic ionic covalent organic framework (MiCOF) masterfully overcomes traditional barriers in selective adsorption, pioneering new functionalities and surface engineering techniques to effectively target and mitigate the impacts of benzimidazoles (BZDs). In previous studies, the idea of designing magnetic nanomaterials through theoretical screening of ionic liquids has been successfully proposed. This work proposed a theoretical and practical design for MiCOFs, aimed at providing a sensitive, selective, rapid, and straightforward method for analyzing trace substances in complex biological matrices. In a gentle one-pot process, the surface of Fe3O4 was coated with covalent organic frameworks (COFs) layer, followed by the modification with amino acid ionic liquid (AAIL) through covalent radical polymerization, facilitated by the abundant unsaturated vinyl groups present. This resulted in MiCOFs (Fe3O4@COF-AAIL) with a stable structure. Compared to unmodified Fe3O4@COF, Fe3O4@COF-AAIL exhibited excellent adsorption selectivity for BZDs. This enhanced selectivity is primarily due to the strong hydrogen bonds and π-π interactions between AAIL and BZDs, aligning well with COSMO-RS theoretical screening predictions. The development of magnetic dispersive solid-phase extraction (MDSPE) enabled rapid processing of BZDs in plasma with low matrix effects (0.9–1.3). This study not only validates a robust framework for the selective separation of trace contaminants in complex biological matrices but also advances the design and application of MiCOFs, setting a new paradigm in material science that could transform the design of novel materials for specific tasks.

Polymerization-induced self-assembly amino acid ionic liquid/poly(ethylene oxide) thin-film composite membranes for CO2 separation

It is well known that crosslinking poly(ethylene oxide) (PEO) membranes exhibit high CO2/N2 solubility selectivity, and are suitable for separating CO2 from flue gas. However, the high CO2/N2 selectivity is temperature sensitive and decreases rapidly with increasing temperature. To overcome this deficiency, imidazolium-based amino acid ionic liquids (AAILs) are introduced into the PEO membranes. A series of (AAILs-PEO)/PAN thin-film composite (TFC) membranes were prepared by a polymerization-induced self-assembly process. Due to the hydrogen and Coulomb interactions between the imidazolium ring of AAILs and the ether groups of PEO monomers, the morphology of the selective layer changed from micellar to granular upon the introduction of the AAILs into the PEO membranes, while the chain-segment flexibility and interspacing of the PEO are also changed. Compared with the original PEO/PAN TFC membrane, the (AAILs-PEO)/PAN TFC membranes show much higher CO2/N2 selectivity, which increases from ∼41 to ∼ 74. In addition, the AAILs show strong hydrophilicity, which leads to a significant increase in CO2/N2 selectivity under the wet-gas feed, reaching ∼105. Compared with the original PEO/PAN TFC membranes with CO2/N2 selectivity of ∼10 at 70 °C, the (AAILs-PEO)/PAN TFC membranes show the selectivity of ∼30, coupled with CO2 permeance of ∼1300 GPU at 70 °C. Under the 40: 60 mixtures of CO2: N2, which is a common lime kiln exhaust gas, by using the (AAILs-PEO)/PAN TFC membrane, the CO2 concentration on the downstream side can reach over 90 % at 20 °C and over 70 % at 70 °C, respectively, under a pressure ratio of 5.

Sustainable recovery and recycling of acidic ionic liquid in 5-ethoxymethylfurfural production via bipolar membrane electrodialysis

Acidic ionic liquids have been proven effective as homogeneous catalysts in preparing 5-ethoxymethylfurfural the fuel additive and platform chemical. Homogeneous catalysis specialty and complicated electrolyte composition limited direct recovery of acidic ionic liquids after 5-ethoxymethylfurfural preparation. In this study, a bipolar membrane electrodialysis (BMED)-based strategy was designed for controllably recovering and regenerating acidic ionic liquid 1-butyl-3-methylimidazolium hydrogen sulfate [Bmim][HSO4] after 5-ethoxymethylfurfural preparation from fructose. Key factors in recovery of ionic liquid [Bmim][HSO4] were studied to ascertain the technical and financial feasibility of the electrodialysis-assisted strategy. The maximum recovery ratio of [Bmim][HSO4] approached 96.2% and the minimum recovery cost was less than 0.1% of [Bmim][HSO4] purchase cost. Insight developed by the work revealed a viable solution for efficient and integral recycling of acidic imidazole ionic liquid in the high-value conversion of biomass.

In–depth understanding on the mechanism of ionic liquid-assisted enhancement of electrochemical CO2 reduction to formic acid

Although extensive research has been conducted on the electrochemical CO2 reduction reaction (CO2RR) using ionic liquid (IL) + acetonitrile and ILs + acetonitrile + H2O systems, it is a challenge to explain why ILs facilitate electrochemical CO2 reduction and why different ILs exhibit varying catalytic effects. In this paper, we utilized commercially available copper electrodes as the working electrode and employed three ILs (i.e., 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([BMIM][Tf2N])) as one of the additive components of electrolytes for electrochemical CO2RR. The relationship between the performance of electrochemical CO2RR to formic acid (FA) and different IL structures in binary and ternary systems was investigated through experiments. The mechanism of performance of electrochemical CO2RR to FA enhanced by ILs in the binary systems was explored at the molecular level through density functional theory (DFT) calculations. Furthermore, the role of H2O was elucidated in the ternary IL + acetonitrile + H2O system.

Structures and hydrogen bonds of -SO3H functionalized acid ionic liquids

Brønsted acidic ionic liquids (BAILs) are clean and versatile replacements for traditional homogeneous acid catalysts and have attracted much attention as efficient catalysts for the synthesis of valuable chemicals. It’s critically important to understand the structural properties of BAILs from the molecular level. In this work, we studied a series of −SO3H functionalized acidic ionic liquids by density functional theory (DFT) calculations, and the most stable geometries were obtained by global semiempirical quantum mechanical search. The most stable structures of cations are formed when more intramolecular H-bonds exist. For BAILs clusters, intramolecular and intermolecular H-bonds coexist and play a critical role in the stability of the system. The interaction energy decreases with increasing alkyl chain length. When the alkyl chain was replaced by −SO3H groups, the interaction energy increased due to more H-bonds formed with the anions. The quasi-3D network is formed in the BAILs clusters and the electrostatic interaction plays a critical role in stabilizing the ion clusters. This work helps to understand the microcosmic interactions of BAILs in-depth and design them in a “task-specific” way.

RSM and ANN methodologies in modeling the enhanced biodiesel production using novel protic ionic liquid anchored on g-C3N4@Fe3O4 nanohybrid

Herin, a new nanohybrid acid catalyst was fabricated for the efficient biodiesel production. At the first, magnetic porous nanosheets of graphitic carbon nitride (g-C3N4@Fe3O4) was prepared and then functionalized with sulfonic acid. Next, the preparation of the catalyst was completed by mixing this surface modified support with n-methyl imidazolium butyl sulfonate zwitterion to achieve non-covalent immobilized acidic ionic liquid on g-C3N4@Fe3O4 support. The catalyst underwent characterization through various techniques such as 1H and 13C NMR, FTIR, SEM, TEM, TGA, EDX and BET which revealing that the magnetic support loaded acidic ionic liquids via a robust charge interaction effect enabling the one-pot production of biodiesel from low-quality oils. Furthermore, the catalyst could be simply recovered using a permanent magnet and reused multiple times without a significant decline in catalytic activity. Consequently, the solid catalyst based on ionic liquids holds promise for the sustainable and eco-friendly production of biodiesel from low-quality oils. Furthermore, Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) were used to model the yield and various process parameters. The findings underscore the enhanced predictive capabilities of ANN in comparison to RSM.

Water Purification Using Choline-Amino Acid Ionic Liquids: Removal of Amoxicillin.

Antibiotics are the main active pharmaceutical ingredients (APIs) for the treatment and prevention (prophylaxis) of bacterial infections, for which they are essential for health preservation. However, depending on the target bacterial strain, an efficient treatment may imply weeks of continuous intake of antibiotics, whose unmetabolized fraction ends up in the wastewater system by human and animal excreta. The presence of these chemical compounds in wastewater is known to damage aquatic ecosystems and cause antibiotic resistance of pathogenic agents, which threatens the future application of these medicines. Aqueous two-phase systems (ATPSs), an emergent extraction technology for biomolecules such as proteins and vitamins, could provide more eco-friendly and cost-effective extractive alternatives given their nontoxicity and low energetic requirements. Moreover, choline-amino acid ([Ch][AA]) ionic liquids (also known as CAAILs or ChAAILs) are considered one of the greenest classes of ionic liquids due to their favorable biocompatibility, biodegradability, and ease of chemical synthesis. In this work, partition studies of amoxicillin were performed in three ATPSs containing dipotassium hydrogen phosphate (K2HPO4) and the CAAILs (cholinium l-alaninate, [Ch][Ala]; cholinium glycinate, [Ch][Gly]; and cholinium serinate, [Ch][Ser]) at 298.15 K and 0.1 MPa. To better characterize the extract and reduce errors in quantification, the effect of pH on the intensity and stability of the UV-vis spectra of amoxicillin was studied prior to the partition studies, and computational chemistry was used to validate the molecular structure of the synthesized ionic liquids. During experimental determinations, it was observed that the extraction of amoxicillin was favored by less polar ionic liquids, achieving maximum partition coefficients (K) and extraction efficiencies (E) of K = (16 ± 6)·101 and E / % = 97 ± 2, respectively, for {[Ch][Gly] (1) + K2HPO4 (2) + Water (3)} in the longest tie-line.

Oxidative and Extractive Desulfurization of Fuel Oils Catalyzed by N-Carboxymethyl Pyridinium Acetate and N-Carboxyethyl Pyridinium Acetate Acidic Ionic Liquids: Experimental and Computational DFT Study

Oxidative and Extractive Desulfurization of Fuel Oils Catalyzed by <i>N</i>-Carboxymethyl Pyridinium Acetate and <i>N</i>-Carboxyethyl Pyridinium Acetate Acidic Ionic Liquids: Experimental and Computational DFT Study

Extraction of Dibenzyl Disulfide from Transformer Oils by Acidic Ionic Liquid.

In recent years, dibenzyl disulfide (DBDS) in transformer oils has caused many transformer failures around the world, and its removal has attracted more attention. In this work, nine imidazolium-based ionic liquids (ILs) were applied as effective, green desulfurization extractants for DBDS-containing transformer oil for the first time. The results show that the desulfurization ability of the ILs for DBDS followed the order of [BMIM]FeCl4 > [BMIM]N(CN)2 > [BMIM]SCN > [BMIM](C4H9O)2PO2 > [BMIM]MeSO4 > [BMIM]NTf2 > [BMIM]OTf > [BMIM]PF6 > [BMIM]BF4. Especially, [BMIM]FeCl4 ionic liquid had excellent removal efficiency for DBDS, with its S partition coefficient KN (S) being up to 2642, which was much higher than the other eight imidazolium-based ILs. Moreover, the extractive performance of [BMIM]FeCl4 increased with an increasing molar ratio of FeCl3 to [BMIM]Cl, which was attributed to its Lewis acidity and fluidity. [BMIM]FeCl4 ionic liquid could also avail in the desulfurization of diphenyl sulfide (DPS) from model oils. The experimental results demonstrate that π-π action, π-complexation, and Lewis acid-base interaction played important roles in the desulfurization process. Finally, the ([BMIM]FeCl4) ionic liquid could be recycled five times without a significant decrease in extractive ability.

Bifunctional pyridinium-based Brønsted acidic porous ionic liquid for deep oxidative desulfurization

Porous ionic liquids have been highlighted with special interest for their desirable catalytic activity and extraction properties. Herein, bifunctional porous ionic liquids (denoted UiO-66-BAPILs) were synthesized by dispersing UiO-66 into a pyridinium-based Brønsted acidic ionic liquid ([BSPy][CF3SO3]) for oxidative desulfurization. The permanent cavity of UiO-66 moiety in UiO-66-BAPILs was validated as well-preserved by the SO2 uptake experiments and molecular size simulations. Under the optimum reaction conditions, the sulfur removal could reach up to 99.5% with hydrogen peroxide as the oxidant. Additionally, bifunctional UiO-66-BAPILs were deemed as both extractants and catalysts during the reaction. A possible mechanism has been proposed that UiO-66-BAPILs extract the aromatic sulfur compounds via π···π interactions and C-H···π interactions and meanwhile oxidize them with peroxysulfonic acids and •OH radicals. These findings will open up new avenues to facilitate the catalytic oxidation performance by constructing bifunctional Brønsted acidic porous ionic liquids.