Amino Acid Ionic Liquids Research Articles

CO2/CH4 Separation in Amino Acid Ionic Liquids, Polymerized Ionic Liquids, and Mixed Matrix Membranes.

The ability to efficiently separate CO2 from other light gases using membrane technology has received a great deal of attention due to its importance in applications such as improving the efficiency of natural gas and reducing greenhouse gas emissions. A wide range of materials has been employed for the fabrication of membranes. This paper highlights the work carried out to develop novel advanced membranes with improved separation performance. We integrated a polymerizable and amino acid ionic liquid (AAIL) with zeolite to fabricate mixed matrix membranes (MMMs). The MMMs were prepared with (vinylbenzyl)trimethylammonium chloride [VBTMA][Cl] and (vinylbenzyl)trimethylammonium glycine [VBTMA][Gly] as the polymeric support with 5 wt% zeolite particles, and varying concentrations of 1-butyl-3-methylimidazolium glycine, [BMIM][Gly] (5-20 wt%) blended together. The membranes were fabricated through photopolymerization. The extent of polymerization was confirmed using FTIR. FESEM confirmed the membranes formed are dense in structure. The thermal properties of the membranes were measured using TGA and DSC. CO2 and CH4 permeation was studied at room temperature and with a feed side pressure of 2 bar. [VBTMA][Gly]-based membranes recorded higher CO2 permeability and CO2/CH4 selectivity compared to [VBTMA][Cl]-based membranes due to the facilitated transport of CO2. The best performing membrane Gly-Gly-20 recorded permeance of 4.17 GPU and ideal selectivity of 5.49.

Cost-Effective Preparation of Carbonic Anhydrase with Superior Performance for Assisting Amine and Amino Acid Ionic Liquid Blends in CO2 Absorption and Desorption

Cost-Effective Preparation of Carbonic Anhydrase with Superior Performance for Assisting Amine and Amino Acid Ionic Liquid Blends in CO₂ Absorption and Desorption

Evaluation of rheological properties and tribological properties of choline/acetylamino acid ionic liquids at different frequencies

With the increasing average lifespan of human beings, the wear and tear caused by daily activities on joints will also escalate. Consequently, there is a growing focus on the development of green, environmentally friendly, and biocompatible non-toxic lubricating materials. The presence of dual chemical active centers in natural amino acids results in anions and cations that lead to precipitation and poor lubrication effects in traditional choline amino acid ionic liquids. In this study, nine types of choline acetyl-amino acid ionic liquids ([Ch][Ac-AA]ILs) were synthesized using acetylated amino acids (Ac-AA) as anions and choline (Ch) as cations. The physicochemical properties and tribological behavior of [Ch][Ac-AA]ILs at different frequencies were evaluated. The results demonstrated that [Ch][Ac-AA]ILs exhibited excellent tribological properties and maintained effective lubrication even under high-frequency friction conditions compared to sodium hyaluronate (HA-T). This performance was attributed to the carbon chain length and functional group composition of [Ch][Ac-AA]ILs' anions. Energy dispersive spectroscopy and X-ray photoelectron spectroscopy analysis revealed that the superior lubrication performance of [Ch][Ac-AA]ILs was associated with the formation of chemical reaction films and physical adsorption films on the surface of friction pairs. This research enriches our understanding of [Ch][AA]ILs-based lubrication systems while providing valuable insights for selecting joint lubricants suitable for different activity frequencies.

Theoretical insight into the chemo-absorption mechanism of amino acid ionic liquids on CO2

Amino acid ionic liquids (AAILs) are acknowledged as potential solvents for CO2 adsorption. However, the mechanism of AAILs adsorbing CO2 has not reached a consensus, which limited the development of high adsorption-performance AAILs. In this work, the mechanism of selected AAILs consisting of 1-Ethyl-3-methylimidazolium ([EMIM]+) cation and amino acids anions ([AA]−) adsorbing CO2 were investigated using density functional theory (DFT) calculations. The nature of the weak interactions between the ionic pairs was found to be hydrogen bonds. The amine group of [AA]− is highly likely to serve as the reactive site to adsorb CO2 with formation of zwitterions. The AAILs-CO2 were discovered to generate carbamic acid through proton transfer in zwitterions. In comparison, the generation of carbamic acid in [EMIM][Gly]-CO2 is a kinetically favorable reaction while in [EMIM][His]-CO2 it is the most thermodynamically favorable, which indicates faster adsorption of CO2 by [EMIM][Gly] and easier adsorption by [EMIM][His]. Furthermore, it was found that the presence of the cation [EMIM]+ weakens the interaction between the amino acid anion and CO2 at different reaction steps. This work revealed the fundamental chemo-absorption mechanism details of AAILs towards CO2, which contributes to rational development of AAILs with optimal CO2 absorption properties.

Molecular dynamics studies on the thermodynamic and structural properties of hydrogen bonds in a novel mixture of dual amino acid ionic liquid – H2O

Amino acid ionic liquid - H2O mixtures have been widely used in recent years. Molecular dynamics (MD) simulations were used to investigate the nanostructures and interactions of two kinds of amino acid ionic liquids, 3–propyl-tributyl-alanine phosphate ([aP4443][Gly]) and 3-propyl-tributyl-alanine phosphate ([aP4443][Ala]) at different water molar fractions (xw = 0 – 0.95). Analysis of volume property showed that there were hydrogen (H) bonds between water molecules and ionic liquids, and the nanostructures of the mixture changed dramatically at about xw = 0.7. MD simulations showed that with the increase of water concentration, the structural correlations between anion - cation, cation - water, anion - water and water - water weakened and the relaxation time of H bonds decreased. The water molecule oxygen atoms competed with the anion carboxyl group to form H bonds with the amino group of the cation. Strong H bonds were also observed between anions and water molecules. Water molecules had different aggregation states at different water concentrations. In the concentrated ionic liquids – H2O mixtures, the anions and cations formed a stable network structure, and the H bonds in the system mainly consisted of H bonds between anions - cations. When 0.7 > xw ≥ 0.5, the H bonds between anion - water were the main component of H bonds in the system. When xw ≥ 0.7, the number of water - water H bonds in the mixture increased rapidly, the diffusion coefficients of the anions and cations increased exponentially, and the stable network of the ionic liquids was destroyed. The ion aggregation region was gradually divided by water molecules. When xw ≥ 0.9, water molecules were interconnected to form a large water network structure, and ionic liquids were gradually dissolved in the water molecules.

Influence of detergents and amino acid ionic liquids on the stability of azurin

Influence of detergents and amino acid ionic liquids on the stability of azurin

Investigation of the stability of myoglobin in the presence of amino acid ionic liquids

Investigation of the stability of myoglobin in the presence of amino acid ionic liquids

Bioinspired Herbicides-Ionic Liquids or Liquid Cocrystals?

This research provides information about combinations of several amino acids, including l-proline (Pro), l-arginine (Arg), and l-histidine (His), with phenoxyacetic acid herbicides (MCPA and 2,4-D). Five amino acid ionic liquids (AAILs), one amino acid higher-melting salt (AAHMS), and two amino acid liquid cocrystals (AALCs) were obtained in high yields (>90%). The ionization of the six new structures was confirmed by NMR, IR, and molecular modeling. X-ray crystallography was used to definitively confirm the binding location of the mobile hydrogen. Furthermore, we propose a computational method for estimating the energy of specific hydrogen bond(s) in AAIL crystals based on the NBO and QTAIM hydrogen bond parameters obtained by model calculations. An in-depth analysis of the structures allowed to answer the question posed in the title, ionic liquids or liquid cocrystals? AAILs based on arginine and histidine were obtained. In contrast, combining proline with MCPA and 2,4-D led to AALCs. Finally, the compounds were analyzed to measure their herbicidal activity. These studies proved that the novel form of MCPA or 2,4-D improved its ability to control weeds compared to commercial formulations containing the same active ingredients.

On the Key Influence of Amino Acid Ionic Liquid Anions on CO2 Capture.

Amino acid ionic liquids (AAILs) are promising green materials for CO2 capture and conversion due to their large chemical structural tunability. However, the structural understanding of the AAILs underlying the CO2 reaction dynamics remains uncertain. Herein, we examine the steric effects of AAIL anions with various chemical structures on CO2 capture behavior. Based on ab initio free-energy sampling, we assess reaction mechanisms for carbamate formation via a two-step reaction pathway with a zwitterion intermediate undergoing dynamic proton transfer. Our results show that free-energy barriers for carbamate formation can be significantly reduced as the degree of steric hindrance of the anions decreases. Further analyses reveal that reduced steric hindrance of anions causes markedly stronger intermolecular interactions between zwitterion and anions, leading to an increased kinetically favorable intermolecular proton transfer for carbamate production. We also describe the correlation strength between intramolecular interactions within the zwitterion and intermolecular interactions between the zwitterion and anions. We conclude that the favored structural flexibility due to the less steric hindrance of the zwitterion leads to enhanced intermolecular interactions, facilitating proton transfer to nearby AAIL anions for carbamate formation. Our study provides invaluable insight into the influence of various degrees of steric hindrance of the AAIL anions governing CO2 chemisorption. These findings may aid in the design of optimal AAIL solvents for the CO2 capture process.

Rheological properties of water-based amino acid ionic liquids

The rheological properties and zero-shear viscosity of water-based lubricants (WBLs) containing amino acid ionic liquids (AAILs) were investigated using both equilibrium (EMD) and non-equilibrium molecular dynamics (NEMD) simulations. We also performed experimental measurements to validate the simulations. The simulations demonstrated that adding AAIL additives to water increased both the shear viscosity and zero-shear viscosity. We added tetrabutylphosphonium (P4444) as a cation and three different amino acids, serine (Ser), lysine (Lys), or phenylalanine (Phe), as anions. We varied the AAIL concentration from 5 to 10 wt. % for tetrabutylphosphonium-serine (P4444-Ser) ionic liquid additives, showing that AAILs increased water viscosity by 68%–125%, depending on concentration. The P4444-Ser WBLs also exhibited a significantly higher first normal stress difference than water, meaning they could support more load in lubrication. The improved rheology persisted over a wide range of shear rates up to ∼1011 s−1. We have extracted full rheological parameters by fitting data into Cross, Carreau–Yasuda, and Eyring models, including zero-shear viscosity and critical shear rates of onset shear thinning. The experimental values of zero-shear viscosity were close to zero-shear viscosity results obtained from fitting NEMD results to these models, demonstrating the high fidelity of the molecular model. We explored the formation of hydration shells around amino acid anions as a marker for low friction behavior. These findings suggest that AAIL WBLs can be potentially low-friction and biodegradable lubricants in tribological applications.

Effect of choline amino acid ionic liquids on maize seed germination and endogenous plant hormone levels.

Prior research has established choline-based ionic liquids (ILs) as safe for various organisms. However, their impact on plants has been underexplored. To identify effective eco-friendly ILs, we synthesized seven choline amino acid ([Chl][AA]) ILs and analyzed their physiological influence on maize seed germination. In contrast to the traditionally used N-octyl pyridinium bromide IL, these seven [Chl][AA] ILs exhibited substantially lower toxicity. Moreover, within a broad treatment concentration range (10-100 mg L-1), these ILs notably enhanced maize germination indices and root and shoot growth. Specifically, treatment with 100 mg L-1 choline tryptophan resulted in a 21.2% increase in germination index compared to those of control maize. Compared to the control, the application of choline serine, choline aspartic acid, choline phenylalanine, and choline tryptophan at 100 mg L-1 led to respective increases of 23.9%, 21.5%, 22.5%, and 24.5% in maize shoot length. Analysis of endogenous hormones and free amino acid contents revealed elevated levels of growth-promoting plant hormones (gibberellic acid and zeatin) in maize shoot tips, as well as increased contents of major amino acids (glutamate, glycine, and arginine) following treatment with different [Chl][AA] ILs at 100 mg L-1. These findings indicate that [Chl][AA] holds promise for the development and application of novel low-toxicity ILs.

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.

Amino acid ionic liquids as efficient catalysts for CO2 capture: A combined static and dynamic approach

Amino acid ionic liquids (AAILs) have gained significant attention as green solvents that are biocompatible, biodegradable, and useful in various applications, including catalysts, absorbents, and solvents. This study investigates the detailed interactions of three amino acid anions (glycine [Gly]-, histidine [His]-, and arginine [Arg]-) with the cation 1-methoxylbutyl-3-methylimidazolium [MOBMIM]+ and their role in CO2 absorption using quantum mechanical calculations and molecular dynamics (MD) simulations. The Density Functional Theory (DFT) calculations elucidate the reaction mechanisms underlying CO2 absorption and cycloaddition, and facilitate a comparative analysis of the impact of different amino acids on these reactions, and the synergies between them. Notably, arginine displays superior CO2 absorption capacity in comparison to glycine and histidine. Additionally, the cycloaddition reaction with CO2 exhibits a lower energy barrier when arginine is involved. Insights from the MD simulations highlight the higher level of electrostatic interaction between [MOBMIM]+[Arg]- and CO2, relative to the other studied molecules. Moreover, the Lennard Jones interaction emerges as the dominant type of interaction in these systems. The diffusion coefficient for CO2 was highest when interacting with [MOBMIM]+[Gly]-, followed by [MOBMIM]+[Arg]-. Consequently, both MD and DFT investigations converge to suggest that [MOBMIM]+[Arg]- followed by [MOBMIM]+[Gly]- may serve as advantageous choices for CO2 fixation and cycloaddition. The findings from this study underscore the considerable potential of the investigated AAILs as materials conducive to CO2 capture and utilization, thus paving the way for the integration of CO2 capture into valuable chemical products.

Biodiesel synthesis through soybean oil transesterification using choline-based amino acid ionic liquids as catalysts

In this study, twelve choline-based amino acid ionic liquids ([Cho][AA]-ILs) were synthesized employing amino acids and choline as raw materials. [Cho][AA]-ILs were effectively employed as catalysts in the biodiesel preparation via the transesterification of soybean oil with methanol. Among the synthesized [Cho][AA]-ILs, cholinium arginate ([Cho][Arg]) was selected as the appropriate catalyst. To optimize the primary experimental reaction conditions (methanol to oil molar ratio, catalyst load, reaction temperature, and reaction time), an experimental design was achieved by the A response surface methodology (RSM) based on the Box-Behnken design (BBD). The maximum biodiesel conversion of 98.58% was achieved with the [Cho][Arg] catalyst under the following optimal conditions: methanol to oil molar ratio of 9.13:1, catalyst load of 14.75%, a reaction time of 56.44 min and temperature 81.41 °C. A first-order kinetic of [Cho][Arg]-catalyzed transesterification of soybean oil with methanol was shown with activation energy and a pre-exponential factor of 10.06 kJ·mol−1 and 1.1707 min−1, respectively. The ionic liquid [Cho][Arg] is a promising, easy to synthesize, and biodegradable catalyst that can replace traditional catalysts for the synthesis of biodiesel.

Novel amino acid ionic liquids as messenger of multi-tertiary-amines solutions for highly efficient capture of CO2

Carbon capture, utilization, and storage (CCUS) are among the key technologies to achieve large-scale carbon emission reduction globally. Amino acid ionic liquids (AAILs) featuring biodegradability and biological activity are capable as eco-friendly absorbents for CO2 capture. Herein, a series of novel AAILs are proposed via one-step hydrolysis of cheap lactams, which can act as messengers to facilitate aqueous solution of multi-tertiary-amines fast and pronounced absorption of CO2. Dynamic absorption experiments were carried out to indicate that [N1111][Maba]-PMDETA-50 % showed a larger apparent absorption rate constant (0.282 min−1) than that of MDEA solution (0.043 min−1), demonstrating the activated role of AAILs. [N1111][Maba]-PMDETA-50 % shows the exceptional absorption capacity of 0.162 g (1.0 bar) or 0.095 g (0.1 bar) of CO2 per g absorbent at 313.2 K, respectively, surpassing all the reported formulated solution. The facilitated absorption mechanism is also illuminated from the NMR spectra. The regeneration heat (equal to absorption enthalpy) was calculated to be − 55.7 kJ·mol−1 from absorption isotherm of three different temperatures. The recyclability was evaluated from the vacuum regeneration (ten consecutive absorption–desorption cycles) and dynamic thermal regeneration, achieving the regeneration efficiency of more than 95 % and 99 %, respectively. All these experimental data indicate that the AAIL-based multi-tertiary-amines aqueous solution may be good candidate absorbent in terms of rapid efficient capture of CO2.

Mass transfer and reaction mechanism of CO2 capture into a novel amino acid ionic liquid phase-change absorbent

In order to overcome high heat duty and poor regeneration efficiency of existing chemical absorbent, a novel aqueous amino acid ionic liquids (AAILs) phase change absorbent with tetraethylenepentamine (TEPA) as cation, L-proline (L-Pro) as anion and N-propanol (NPA) as phase separator was proposed in this study. [TEPAH][Pro]/NPA/H2O owned the maximum absorption loading of 2.01 mol CO2·mol absorbent−1, and the rich phase viscosity was only 8.06 mPa·s. Moreover, its desorption efficiency was 84.4% while the 5th cyclic loading kept above 1.61 mol CO2·mol absorbent−1. With the presence of NPA, the rich phase only accounted for 41% of the total volume while it contained 99.3% of CO2 products. The heat duty was only 2.39 GJ·t CO2-1, which was 37% lower than that of 30 wt% ethanolamine (MEA) aqueous solution. Meanwhile, the reaction mechanism and product distribution were revealed by 13C NMR and the mass transfer kinetics was investigated using the wetted wall column. The products in the rich phase mainly consisted of carbamate, hydrogen carbonate, propyl carbonate and water while the main component of the lean phase was NPA. The reaction followed a fast pseudo-first order reaction. At 313.15 K, the rate constant of fresh absorbent was 51346 s−1, which showed a decreasing trend with the increase of absorption loading at 313.15 K. The second order reaction rate was calculated by: k2 = 9.88 × 109exp(-3591.2/T), where the reaction activation energy was only 29.86 kJ·mol−1.

Adsorption mechanism of amino acid ionic liquids on the N-doped graphene surface for electrochemical double layer capacitors: A density functional theory study

BackgroundThe interfacial interaction between amino acid ionic liquids (AAILs) and graphene (Graphene and N–Graphene) is crucial for understanding the behavior of electrolytes in supercapacitors and ion–batteries. Studying the adsorption mechanism of AAILs on graphene surfaces is the subject of this work. MethodsIn this study, we employed the density functional theory to reveal adsorption process. The binding energies, thermochemistry, quantum molecular descriptors, charge transfer, quantum theory of atoms in molecules, noncovalent interaction and energy decomposition analysis were investigated. Significant findingsThe adsorption process spontaneously proceeded, and the highest occupied molecular orbital–lowest unoccupied molecular orbital energy gap was reduced slightly upon AAILs adsorption. Nitrogen doping significantly guides the local distribution of electrons and improves the combination of ions, and charge transfer between AAILs and N–Graphene was greater than between AAILs and Graphene. Thus, N–Graphene might exhibit better performance than Graphene. Furthermore, the adsorption was noncovalent in nature, which is crucial to the diffusion of ions in electrolyte–electrode systems. The above results could offer a new angle of view on graphene–AAIL and help in designing novel systems for electrochemistry applications.

Creating a new biocatalytic complex with extremolipases and biocompatible ionic liquids for improved transesterification reactions

The ongoing energy crisis has spurred increased research into sustainable and more competitive methods for producing biofuels, including biodiesel. In this context, the focus of the current study is to underscore the viability of investing in a novel biocatalytic complex. This complex incorporates extremophilic lipases and biocompatible ionic liquids with the aim of achieving exceptionally high conversions in transesterification reactions without generating glycerol. Through a meticulous screening process encompassing various amino acid and dipeptide-based ionic liquids from the ammonium family, cholinium glycinate turned out to be the optimal choice. This selection was driven not only by its enhanced compatibility with a commercially available Candida antarctica lipase B (CaLB) but also with extremophilic enzymes synthesized in-house, derived from halophilic (Halomonas spLM1C) and thermophilic (Thermus thermophilus HB27) strains. Following rigorous testing of both free and immobilized enzymes, the ideal concentration of the ionic liquid in transesterification reactions was determined to be 1% relative to the sunflower oil content. Comparative analysis of conversion rates between immobilized thermophilic lipase and immobilized CaLB revealed the efficacy of the proposed approach. Maximum conversions were found to increase by 20%, with specific conversion rates soaring by approximately 180% when utilizing the immobilized thermophilic lipase. In conclusion, this research ushers in new prospects for advancing the competitiveness of biocatalytic solutions in glycerol-free transesterification reactions, underscoring its potential to revolutionize the landscape of sustainable energy production.

Probing the local structures of Choline-Glycine Electrolytes: Insights from ab initio simulations

Amino acid ionic liquids have garnered significant attention for their potential in electrochemical energy storage due to their wide electrochemical stability windows and inherent safety. The performance of ChGly as an electrolyte for supercapacitors has been compared to that of highly efficient conventional ionic liquids. However, a thorough understanding of the microstructural characteristics responsible for the enhanced properties of ChGly aqueous solutions remains largely unexplored. In this study, ab initio molecular dynamics simulations were employed to investigate the energetic, structural, transport and spectroscopic properties of ChGly-based pure and aqueous electrolytes. A comprehensive analysis of the cation–anion and water-ion hydrogen bonding was conducted for both electrolyte systems. Structural features were examined using radial and spatial distribution functions, while the vibrational power spectra were analyzed to identify significant differences in intermolecular interactions between pure and aqueous electrolytes, stemming from modified solvation shell structures. The findings presented in this work shed light on crucial structural and spectroscopic distinctions between pure and aqueous ChGly electrolytes, providing valuable insights for further advancements in the field.

Molecular simulation of CO2 capturing by dual functionalized phosphonium-based amino acid ionic liquids

Various solvents have been proposed considering the importance of CO2 gas removal from the environment. Over the past few decades, ionic liquids (ILs) have elicited much attention due to their unique properties. In this regard, capturing the CO2 gas by phosphonium-based amino acid ILs (AAILs) was studied by molecular dynamics (MD) simulation. The effect of cation functionalization was studied. The anion was glycinate, [GLY]-, and the cation was tetrabutylphosphonium, [P4444]+, functionalized by different functional groups including acidic (−COOH), alcoholic (−OH), amine (−ΝΗ2), and ether (−OCH3). Density, absorption energy, radial distribution function (RDF), mean square displacement (MSD), concentration profile, free volume, and fractional free volume were under investigation. According to density values calculated from MD simulation, functionalized AAIL with a carboxylic acid group ([P4444COOH][Gly]) is the most concentrated system with the maximum interaction energy between AAIL and the trapped CO2 gas equal to − 1.917 kcal.mol−1. In addition, the lowest volume variation was observed through this physical absorption. RDF analysis reveals that anion interaction with CO2 gas is the most considerable one in the case of [P4444COOH][Gly] AAIL. The CO2 uptake is 2:1 for functionalized AAILs that shows cation functionalization improves CO2 gas absorption capacity; each mole of [P4444COOH][Gly] AAIL is capable of surrounding 2.11 mol of CO2. Finally, the gas diffusion coefficient is the lowest one in [P4444COOH][Gly] AAIL as the solvent-free volume is observed as a continuous channel to trap CO2 gas with the lowest gas diffusivity parameter.