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This document is a contents list for the journal "Green Chemistry," published by the Royal Society of Chemistry. It features research papers on various topics related to sustainable chemistry, including photocatalytic upgrading of hydroxymethylfurfural, lignin extraction and nanodispersion, selenium-doped carbon materials, and the valorization of bio-renewable glycerol. The journal also includes tutorial reviews on topics such as Pickering emulsion-derived nano/microreactors and the iron ligand-to-metal charge transfer chemistry in water. Additionally, there are perspective papers, communications, and other research papers covering a range of subjects in green chemistry. The papers provide valuable insights into the development of greener and more sustainable chemical processes. [Extracted from the article]

This study shows a functional deep eutectic solvent (DES) employing choline chloride (ChCl) and glyoxylic acid (GA) for lignocellulose fractionation. This DES exhibited a higher pretreatment efficiency (92.15%) than that composed of ChCl and lactic acid (10.36%). Molecular dynamic (MD) simulations indicated that the ChCl : GA DES showed a higher total binding energy (ΔE) with lignin than the ChCl : LA DES, resulting in a higher dissolution of lignin. GA prevented lignin condensation during pretreatment. The stabilized lignin containing 69.39% β-O-4 linkages can be used for phenolic monomer production with a bio-oil yield of 59.60% and lignin-based sunscreen preparation with a SPF of 58.46. The cellulose residues with a mild pretreatment severity exhibited a high enzymatic saccharification yield of 91.99%. Meanwhile, an esterification reaction occurred between cellulose and GA during pretreatment. The inhibition of enzymatic hydrolysis and microbial growth enables the use of functional cellulose to produce antibacterial paper. Furthermore, 96.80% of the DES could be easily recycled and reused for biorefinery purposes. [ABSTRACT FROM AUTHOR]

The document is a contents list of the New Journal of Chemistry, a publication that focuses on various topics in the field of chemistry. It includes a list of articles in the current issue, along with the names of the authors and a brief description of each article. The journal covers a wide range of subjects, such as catalyst synthesis, drug discovery, nanotechnology, and chemical reactions. The document also provides information about the editorial staff and contact details for submitting articles or making inquiries. It concludes with details about subscriptions and copyright. This document serves as a valuable resource for researchers interested in accessing the latest research in chemistry. [Extracted from the article]

For a knowledge-based design of enzyme catalysis in deep eutectic solvents (DESs), the influence of the DES properties (e.g., water activity and viscosity) and the impact of DESs and their individual components must be assessed. This paper investigates three different DESs: choline chloride–glycerol (ChCl–Gly), choline chloride–ethylene glycol (ChCl–EG), and ethyl ammonium chloride–glycerol (EACl–Gly). The specific activity and half-life time of horse liver alcohol dehydrogenase (HLADH) were experimentally determined in these DESs with water contents ranging from 0%–100%. HLADH showed limited activity in neat DESs, which was enhanced by adding water. Experiments with individual DES components of ChCl–Gly were carried out to clarify their individual influence. Glycerol acts as a strong stabilizer for the enzyme, whereas choline chloride's results are deleterious. To understand the experimental findings, molecular dynamics (MD) simulations were carried out to quantify the solvation layer and calculate the spatial distribution of the solvent molecules around HLADH. The experimental and the in silico approach suggests that designing novel DESs with higher glycerol loadings would result in improved media for biocatalysis. This is demonstrated by performing the reduction of cinnamaldehyde to cinnamyl alcohol—a relevant compound for the food industry and cosmetics—in ChCl–Gly (1 : 9 molar ratio), with 20 vol% water to decrease the viscosity. HLADH is highly active and stable under these new conditions, giving promising productivity (15.3 g L−1 d−1). This paper demonstrates that DESs can be designed to be both substrate-solubilizers and enzyme-compatible, opening new research lines for green chemistry and biocatalysis. [ABSTRACT FROM AUTHOR]

In this paper, deep eutectic solvents (DESs), namely choline chloride/ethylene glycol and choline chloride/citric acid, are employed as efficient templating agents for the controlled fabrication of zinc oxide nanostructures with unusual morphology such as petal-aggregated flower-like and cauliflower-like 3D hierarchical structures via a simple hydrothermal approach at 150 °C for 15 h. The obtained samples were characterized by XRD, TEM, SEM, UV-Vis diffuse reflectance spectroscopy and photoluminescence (PL) studies. The XRD analysis confirmed the presence of the hexagonal wurtzite structure of ZnO and the morphology results demonstrated the structure-directing effect of the deep eutectic solvents, which leads to exposure of the {0001} facet. The temperature-dependent growth behaviour of the nanoparticles directly indicated the formation of different shapes owing to the percentage difference in the exposed facet. The photoluminescence spectra showed that the prepared ZnO nanostructures exhibited strong green emission related to oxygen vacancies and defects. The synthesized flower-like ZnO nanostructure showed a higher photocatalytic degradation efficiency toward methyl orange as compared to commercial ZnO powders. [ABSTRACT FROM AUTHOR]

This work focuses on the use of the deep eutectic solvent composed of choline chloride and acetic acid (1 : 2) in the pretreatment of the perennial energy crop Miscanthus, commonly called silvergrass. The pretreatment time and temperature were optimized to achieve a maximum of the glucan and minimum of the lignin contents in the pretreated biomass. In the optimization approach, the maximal glucan recovery in the pretreated solid was also considered. The performed optimization resulted in conditions (2 h 52 min and 150 °C), at which a pretreated biomass contained 74.1 wt% and 9.5 wt% of glucan and lignin respectively, and a glucan recovery was as high as 87.0 wt%. Furthermore, the biocompatibility of deep eutectic solvent was evaluated by using enzymatic hydrolysis washed and unwashed pretreated biomass produced at optimal conditions. The enzymatic hydrolysis of washed biomass resulted in higher glucan and xylan conversion than those achieved from unwashed biomass, deeming the step of biomass washing necessary. This was confirmed by the fractal kinetics modelling that confirmed higher accessibility of glucan for washed biomass than for unwashed Miscanthus sample. [ABSTRACT FROM AUTHOR]

Pretreatment facilitates cost-effective operations on lignocellulosic biomass ranging from densification to deconstruction and bioproduct development. However, determining molecular-level mechanisms behind pretreatment and their effects has remained elusive. Here, we combine computational simulation and experiment to investigate the effects on wheat straw agricultural residue densification of an emerging pretreatment solvent, namely, a deep eutectic solvent (DES) consisting of choline chloride (ChCl) and oxalic acid (OA). Ab initio molecular dynamics indicates that dissociation of lignin from cellulose in lignin–carbohydrate complexes, which does not occur to a significant extent in aqueous solution, is favorable in the DES and occurs via cleavage of the guaiacyl : xylose ether bond linkage by OA. The ensuing hemicellulose removal exposes lignin to the DES which, molecular dynamics simulation indicates, leads to lignin expansion. The resulting changes in wheat straw fiber structure, lignin distribution, and functional group modifications upon DES treatment by scanning electron and fluorescence microscopy along with Fourier-transform infrared spectroscopy. The molecular expansion of lignin enhances inter-particle binding in wheat straw, leading to denser structures under pelletization. The resulting high mechanical stability and combustion properties make the wheat straw a suitable precursor of high-quality densified solids (e.g., solid biofuel). Overall, we shed light on the molecular-level mechanisms involved in DES pretreatment for biomass densification, demonstrated here in the development of a solid biofuel. The approach here illuminates the rational design from first chemical principles of methods to convert lignocellulosic resources into advanced materials. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) are gaining rapid prominence in numerous biocatalysis processes due to their green characteristics, biodegradability, low cost, and simple preparation compared to harsh organic solvents and toxic ionic liquids. However, natural enzymes tend to show activity reduction, even inactivation in the presence of many DESs. Here, we present the first rational design approach to achieve enzymes resistant to both DESs and high temperatures. Using the interaction pattern between DESs and BSLA (Bacillus subtilis lipase A, our model enzyme) derived from all-atom molecular dynamics (MD) simulations, we formulated a solvation-guided engineering strategy. This was established after assessing 33 structural, solvation, and energy observables. We rationally designed and experimentally tested 36 single substitutions, of which 28 (a 77.78% success rate) exhibited improvements in at least two DES cosolvents: choline chloride (ChCl) : acetamide, tetrabutylphosphonium bromide (TBPB) : ethylene glycol (EG), and ChCl : EG. Additionally, through stepwise recombination, we identified two robust BSLA variants, D64H/R107L/E171Y and D64H/R142L, showing stability improvements of up to 4.4-fold and 3.2-fold in three DESs and at 50 °C, respectively. Further MD studies demonstrated that (i) the restricted overall structure but fine-tuned local flexibility and (ii) increased water but decreased DES molecules at substituted sites are two main factors contributing to the enhanced multiple DES resistance. Overall, solvation-guided engineering offers an efficient and rational approach for designing lipases tolerant to DES cosolvents and elevated temperatures, with a considerable potential for adaptation to other enzymes. [ABSTRACT FROM AUTHOR]

Deep eutectic solvent (DES) pulping is a promising alternative to conventional pulping techniques, mainly owing to the favourable solvent properties and reduced environmental impact. DES lignin, however, still awaits complete structural characterisation, especially in terms of the potential incorporation of DES constituents. Here, we describe the structural modification of lignin during lactic acid : choline chloride DES pulping of Miscanthus biomass in unprecedented detail. We show that DES pulping induces β-O-4 aryl ether cleavage and extensive substitution by DES incorporation. The covalent incorporation of both lactic acid and choline was confirmed through saponification of the precipitated lignin and lignin model compound studies. Detailed multidimensional NMR analysis allowed us to validate aliphatic and benzylic lactic acid esterification as well as benzylic choline and lactic acid etherification of β-O-4 aryl ethers. We demonstrate that these reactions occur in all process phases by comprehensive analysis of the precipitated, residual and solubilised lignin fractions, together comprising 93% w/w of the initial lignin in Miscanthus. Covalent lactic acid and choline incorporation occurs independently of biomass type (grass, hardwood and softwood) and can be modulated by water content, reaction duration and temperature. Going forward, these new insights will offer ample opportunities for producing lignins with unique structural features and ultimately will open up new avenues for specific functional ingredient applications. Our work thus clearly advances the DES biorefinery concept and contributes to the valorisation of lignin in general. [ABSTRACT FROM AUTHOR]

Forward osmosis (FO) using deep eutectic solvents (DESs) as the draw solution (DS) was used in liquid mining of lithium from a synthesized brine, which was used as the feed solution (FS). Two DESs (choline chloride: 2 ethylene glycol and choline chloride: 2 levulinic acid) were studied as the DS. The water flux, reverse solute flux, final lithium concentration, and physical properties of commercially available cellulose triacetate membranes were studied experimentally. The performance of the DESs as DS in FO was compared to aqueous inorganic solutions at various concentration levels. Among all the DSs studied, choline chloride: 2 ethylene glycol (ChCl: 2 EG) resulted in the highest water flux (18.25 L m−2 h−1), upgrading the concentration of lithium by up to 3.68 times. In terms of reverse solute flux, the DESs showed lower values compared to the aqueous inorganic DSs tested when the active layer of the membrane was facing the FS. The use of DESs was also found to improve the membrane hydrophilicity and roughness. Freeze concentration (FC) was subsequently used to separate and recover the water that permeated into the DS and reconcentrate the latter for reuse in FO. This work highlights the potential sustainability benefits of the use of FO in lithium extraction, as the integration of FO with green DESs offers a promising liquid mining solution to meet the increasing demand for lithium while mitigating the environmental concerns associated with its extraction. [ABSTRACT FROM AUTHOR]

The industrialization of the recycling of spent lithium-ion batteries presents promising opportunities and challenges. Herein, we developed a strategy of combining task-specific deep eutectic solvent (3,4,5-trihydroxybenzoic acid: choline chloride) dissolution and the following solvent-induced crystallization (SIC) for upcycling LiCoO2 (LCO) battery cathodes into cobalt-polyphenol networks. It has been confirmed that protic solvents (ethylene glycol, methanol, ethanol, and H2O) serve as effective inducing agents to achieve this strategy, playing a role in: (1) regulating the coordination environment of metal ions, initiating the self-assembly process with polyphenol anions and (2) provoking the precipitation of metal-polyphenol network particles (MPNPs) by altering the solubility. Comprehensive research indicated that when organic building blocks (phenolic acid, polyphenol compounds and their derivatives), Cl−, and inducing agents concurrently exist in the system, one-step conversion from LCO to MPNPs could be achieved. A tandem scheme is proposed based on the research for upcycling LCO into MPNPs, which are applied widely in separation, purification and catalysis. Experiments on ternary electrode materials demonstrated the robust generalizability of our strategy. This work provides valuable insights for the industrialization of spent LCO battery recycling and its transformation into novel materials. [ABSTRACT FROM AUTHOR]

Sweet cherry pomace waste (CPW) obtained after juice production still contains high amounts of dietary fiber and added value compounds such as polyphenols. For this reason, it can be employed as renewable feedstock to produce novel commodities, bioactive compounds and bio-functional materials. In this study, a sustainable biorefinery approach has been developed combining the use of natural deep eutectic solvents (NADESs) for the recovery of polyphenolic compounds and bio-based ionic liquids (bio-ILs) for the treatment and conversion of the remaining lignocellulosic residue into an ionogel. The extraction efficiency and selectivity of different classes of (NA)DESs were evaluated varying both the hydrogen bond acceptor, HBA (choline chloride (ChCl), betaine (Bet) and L -proline (Pro)) and the hydrogen bond donor, HBD (carboxylic acids and polyols). The extracted phenolic compounds were qualitatively and quantitatively analyzed by UHPLC-HR-ESI-MS leading to the identification of more than 25 compounds, classifiable into four main subclasses (phenolic acids, flavonoid glycosides, flavonoid aglycones, and anthocyanins). The majority of ChCl-based DESs improved the total phenol extraction compared to classical solvents (up to twice). ChCl : ethylene glycol 1 : 2 was identified as the best performing system in terms of total phenolic content (total phenol 759 ± 85 μg g−1 of dried CPW) and was employed as the extraction medium for further optimization of the operative conditions and recycling study. The solvent was quantitatively recovered for three cycles with retention of the extraction efficiency towards all the identified subclasses of phenols. Finally, cholinium arginate (ChArg) allowed for obtaining cellulose enriched material (35 wt% of dried biomass) that was subsequently dissolved at 2 wt% in cholinium levulinate (ChLev) to prepare a weak physical ionogel, a functional biomaterial potentially useful in medical and pharmaceutical sectors. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) are widely used as recyclable green solvents for the separation of lignin from lignocellulosic biomass. However, the poor permeability of DES solution limits the green advancement of separation systems. In addition, lignin fragment molecules are susceptible to repolymerization reactions during separation, resulting in reduced lignin reactivity. In this study, a DES consisting of choline chloride (ChCl) as a hydrogen acceptor, 5-sulfosalicylic acid (5Saa) as a hydrogen donor, and a certain amount of γ-valerolactone (GVL) as an additive was designed. The system not only efficiently fractionated lignin from poplar (71.35%), but also selectively retained almost complete cellulose (retention 92.87%) under the optimal fractionation (ChCl/5Saa/GVL molar ratio 1/4/15, temperature 120 °C, time 3.0 h). Pre-crushing processing of raw materials was avoided as the new DES solution has stronger permeability compared to the previous DES solution. Selective deconstruction of lignocellulose was achieved due to a strong hydrogen network structure. The lignin fragments were effectively dissolved. The results showed that the stability of the carbo-positive active intermediates was enhanced by ChCl–5Saa/GVL. Lignin with a low molecular weight (2305 g mol−1), high purity (98.77%) and high total phenolic hydroxyl content (6.92 mmol g−1) was obtained. Homogeneous lignin nanoparticles (LNPs) were prepared with an average particle size of 23 nm. LNPs had high dispersion stability and excellent UV shielding properties. The green advancement of the new DES has been significantly improved and the efficient fractionation of high-value lignin was realized. [ABSTRACT FROM AUTHOR]

L -Cysteine is a common amino acid that plays an important role in human livelihood and production. Therefore, a novel method for the simultaneous quantitative and qualitative determination of L -cysteine by a colorimetric detection system is proposed. As a viable oxidase mimic, [N4444]Cl-G/MnO2, which consisted of MnO2 nanosheets functionalized by a tetrabutylammonium chloride–glycerol ([N4444]Cl-G) based deep eutectic solvent (DES) was fabricated. Owing to the oxidation of MnO2 nanosheets, [N4444]Cl-G/MnO2 could oxidize the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into a blue product (oxTMB) with the characteristic UV–vis spectrum absorbance at 652 nm. The oxidation of TMB by DES/MnO2 was inhibited when L -cysteine was introduced, and the absorbance decreased proportionally with the increase in L -cysteine concentration. Due to this inhibition effect, a colorimetric detection system ([N4444]Cl-G/MnO2-TMB) was developed for the quantitative determination of L -cysteine. Under optimal conditions, the assay showed good linearity over the concentration range of 0.125–2.00 μg mL−1 with a low detection limit of 5.96 ng mL−1. A study of the inhibition mechanism demonstrated that the sulfhydryl group of L -cysteine could decompose [N4444]Cl-G/MnO2 into Mn2+, thus limiting the conversion of TMB to oxTMB. In addition, the [N4444]Cl-G/MnO2-TMB system was used in test strips for the visual qualitative detection of L -cysteine. The selectivity and test strip results demonstrated the high selectivity, simple operation, and rapid response of the [N4444]Cl-G/MnO2-TMB system for the qualitative detection of L -cysteine. Given the satisfying performance of the detection strategy, colorimetric sensing based on the [N4444]Cl-G/MnO2-TMB system is considered to have prospective application value in the quantitative and qualitative detection of L -cysteine. [ABSTRACT FROM AUTHOR]

Eutectic solvents are tunable for targeted applications through the functional groups in their hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD) components, as well as the HBA : HBD composition ratio. This study examines the properties of choline-based eutectics containing imidazole, phenol, pyrrole-2-carbonitrile, and 1,2,4-triazole HBAs, and ethylene glycol, 1,2-propylene glycol, and ethanolamine HBDs. The viscosity, conductivity, degree of hydrogen bonding, thermal stability, and solvatochromic properties are examined as a function of HBA, HBD, and the composition. These studies revealed a predominant dependence of physical properties on the HBD and determined that the strong hydrogen bonding in phenol and imidazole-based systems lead to higher viscosities and lower conductivities – critical parameters for CO2 capture and electrochemical conversion. The developed eutectic solvents were further evaluated in terms of their CO2 capture capacities and electrochemical stabilities. Solvatochromic properties were found to correlate with CO2 capacities, demonstrating the tunability of these solvents for CO2 capture. The quantitative structure–property relationship (QSPR) analysis demonstrated the ability to predict viscosities and CO2 capture capacities (<25% deviation) through a multi linear regression method utilizing five molecular descriptors. This work highlights the role of functionalized HBAs and HBDs in the physical, thermal, and electrochemical properties of eutectic solvents as they relate to CO2 capture and electrochemical processes. [ABSTRACT FROM AUTHOR]

Green and efficient biorefinery strategies are essential for sustainable biomass utilization. This study reported a novel fractionation strategy using deep eutectic solvent–sodium bicarbonate (DES–SB) for full-component utilization of corn stover (CS). The results showed that the addition of SB significantly improved the delignification efficiency (90.03%) compared to that of the neat DES pretreatment (34.64%). As a result, excellent carbohydrate digestibility was achieved (glucose yield, 97.47%; xylose yield, 92.93%). Moreover, the regenerated lignin exhibited high purity (94.31%), excellent thermal stability, a low molecular weight (1593 g mol−1), and good uniformity (1.76), indicating great potential for further value enhancement. NMR analysis indicated the retention of major interunit linkages (45.6% of β-O-4), and the recovered lignin presented a greater number of carboxyl groups and a lower number of p-hydroxyphenyl OH groups as the pretreatment severity increased. Finally, mass balance analysis demonstrated that 1 kg of dry CS could produce 367.03 g of glucose, 171.70 g of xylose, and 143.52 g of lignin. Overall, this study provides a green, high-efficiency, and synergistic DES–SB pretreatment strategy that has great potential for full-component biomass utilization and sustainable industrial biorefinery application. [ABSTRACT FROM AUTHOR]

Starch derivatizations require harsh chemicals as solvents or catalysts, which can negate the green nature of starch-based materials. Often, these reaction systems require several hours to achieve moderate degrees of substitution (DS), drastically reduce molar mass and can result in undesired crosslinking compromising solubility. Here, we report an efficient and sustainable starch esterification with acetic anhydride (AA) and the optimization of the process avoiding initiators in terms of molar ratios, time, and temperature. Furthermore, chromatographic (HPSEC-MALS-dRI) and spectroscopic (FTIR, 1H NMR, 2D HSQC and HMBC, Solid State CP/MAS 13C NMR, TG-IR) tools were implemented to elucidate the chemical composition and structure of the resulting starch acetates and potential intermediate side reaction products over the course of the reaction. Different combinations of choline chloride (ChCl) with several hydrogen bond acceptors (urea, tartaric, malonic, and malic acids) were used as both chaotropic solvents and reaction promoters for starch acetylation. The reaction system comprising 1 : 1 molar ChCl : urea and AA showed good miscibility at 100 °C after 30 min, representing a seemingly homogeneous reaction system while better preserving starch molar mass. Side products emerging from solvent-reagent interactions, such as starch carbamate and acetylurea, were identified. Reaction optimization resulted in no side products, fast reaction rates (36 min), high DS (2.87) and starch loads (20 wt%), and increased reaction throughput and atom economy. Catalyst-free starch acetylation reduced hygroscopicity and increased glass transition and degradation temperatures (162 °C and 397 °C, respectively), while generally keeping a relatively higher molar mass (1.5–2.9 × 106 Da) than traditional starch acetates. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) provide a greener approach to reduce the toxicity of ionic liquids (ILs) when altering the behaviour of polymers. DESs have extraordinary properties such as high solubilising abilities, easy preparation, low volatility, good thermal stability, and cost effectiveness, making them suitable for wider applications in biomedical research. DESs can be used for modulating the behaviour of thermo-responsive polymers (TRPs) to provide successful hybrid functionality very near or at room temperature to achieve better stability. The current study is an attempt to achieve this and demonstrates that the presence of choline chloride : lactic acid, 1 : 2 (CC : LA), betaine : lactic acid, 1 : 2 (BET : LA), proline : lactic acid, 1 : 1 (PRO : LA) and urea : lactic acid, 1 : 2 (U : LA) as DESs can change the performance of a thermoresponsive polymer poly(N-vinylcaprolactam) (PVCL). The thermoresponsive behaviour of PVCL was investigated in this study using a variety of techniques, including steady-state fluorescence, Fourier-transform infrared (FTIR) spectroscopy, and UV-visible spectroscopy. Additionally, the LCST values of PVCL were also examined by temperature dependent dynamic light scattering (DLS) which showed a regular decrease in the presence of DES. Dynamic light scattering was also used to better understand the PVCL's aggregation behaviour in the DES environment. Our results show that DESs are generally ionic or polar protic in nature and that they promote hydrophobic interactions among the biopolymeric chains by providing a hydrophobic environment and significantly promoting the hydrophobic collapse of PVCL. It was observed in this study that the structure of DESs plays a major role in altering the lower critical solution temperature (LCST) of PVCL. Our results shows that U:LA provides the least hydrophobic environment due to its polar nature and that BET:LA exerts the most pronounced extent. The intramolecular hydrogen bonding interactions among urea molecules lead to its lower interactions with the surrounding PVCL polymer and the absence of hydrogen bonding in the betaine moiety favours the intermolecular interactions with PVCL and results in a more prominent decrease in the LCST values of the polymer. All DESs successfully modulated the LCST of PVCL through the exclusion of water molecules around the polymer and thus facilitated faster agglomeration. Notably, the LCST of BET:LA reached 27 °C. This study provides us with a new approach for drug carrier applications. [ABSTRACT FROM AUTHOR]

5-Hydroxymethylfurfural (5-HMF) is the key to unlocking the potential of biomass materials to transform into fuels, materials, and chemicals. In this study, an effective biphasic reaction system composed of a reaction phase (aqueous phase) and an extraction phase (organic phase) was used for the conversion of fructose to 5-HMF. Deep eutectic solvents (DESs) composed of different hydrogen bond donors and hydrogen bond acceptors, the ionic liquid [BMIM]Cl, aqueous choline chloride, aqueous betaine hydrochloride, and ethylamine hydrochloride were used as the reaction phase, and different organic solvents, such as methyl isobutyl ketone (MIBK), dimethyl sulfoxide (DMSO), toluene, ethyl butyrate, and gamma-valerolactone (GVL), were used as the organic phase. Experiments were conducted under optimal conditions simulated using the reaction surface method to obtain the maximum 5-HMF yield. The highest yields of 5-HMF obtained in reactions with DESs were 67.86%, 68.69%, and 71.40% for ChCl : OA, ChCl : Lac, and EaCl : Lac, respectively. However, adding dimethyl sulfoxide and betaine hydrochloride aqueous solution to the fructose conversion system resulted in a maximum yield of 90.42% ± 1.46% of 5-HMF without the use of catalysts. This study also demonstrated that betaine hydrochloride could be effectively reused four times. A 5-HMF yield of at least 80% indicates a green process suited towards sustainable development. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) have been extensively studied for lignin extraction from lignocellulosic biomass due to their easy synthesis, selective lignin dissolution, high recyclability, and other benefits. In this study, lignin in poplar wood was extracted using DESs composed of malic acid (Mal) and choline chloride (ChCl). A two-step treatment approach using DESs was proposed in order to enhance the lignin separation capability of DESs under mild conditions and achieve cellulose purification. The impacts of the Mal/ChCl molar ratio, reaction temperature and time on lignin extraction were examined. 75.3% of lignin was separated from poplar wood using Mal/ChCl (2 : 1) DESs at 120 °C for 4 h. Notably, after two-step DES treatments, 86.9% of lignin was removed, and the delignification efficiency was 21.7% higher than that by one-step treatment at the same temperature and time. Also, the lignin dissolved in DESs was regenerated and characterized by Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), and heteronuclear single quantum correlation (HSQC) spectroscopy. The results suggested that the regenerated lignin has low molecular weight with the β-O-4′ bond eliminated, which could be beneficial for the subsequent modification and development of lignin-based biofunctional materials. [ABSTRACT FROM AUTHOR]

A deep eutectic solvent (DES) containing choline chloride (ChCl) and urea (1 : 2) was introduced as an efficient, cost-effective, reusable, and environmentally benign medium for the metal-free synthesis of α-aminophosphine oxide/phosphonate derivatives from one-pot, three-component hydrophosphorylation reactions of aldehydes, amines, and diphenylphosphine oxides/diethylphosphite. Here ChCl–urea (1 : 2) DES played a dual role, namely that of a solvent as well as an efficient catalyst. Using this protocol, diverse α-aminophosphorous derivatives were obtained in excellent yields after short duration, with decent functional group tolerance. [ABSTRACT FROM AUTHOR]

A novel approach for the allylic alkylation of anilines, hydrazides, indole derivatives and additional interesting nucleophiles is described, which involves the direct use of a variety of allylic alcohols under very mild conditions, such as room temperature, and the use of sustainable deep eutectic solvents (DESs). The search for the optimum DES to be used in the reaction revealed that a simple mixture of choline chloride (ChCl) and lactic acid provides excellent results for a wide range of substrates with high isolated yields. This methodology represents a significant improvement compared to other procedures described in the literature, for which high temperatures, stronger reaction conditions or metal catalysts are usually required. In some cases, this protocol provides the first examples of trapping allylic carbocations with indole derivatives. In addition, challenging nucleophiles such as amides, carbamates, azides or sulfonamides, among others, have also been successfully used. All these features render this procedure an appealing and green alternative compared to other examples reported in the literature on the alkylation of amines by allylic alcohols. Preliminary mechanistic studies using unsymmetrically substituted alcohols support that the reaction could proceed via an SN1 pathway. [ABSTRACT FROM AUTHOR]

HCl regularly yields as a byproduct in the tail gas of pharmaceutical and chemical processes, including chlorination and dechlorination reactions. It is very challenging to obtain value-added pure HCl gas by making the use of a non-aqueous absorbent for the separation and recovery of HCl with both high efficiency and excellent reversibility. In this study, a new type of choline chloride-glycerol (ChCl-Gly) deep eutectic solvents (DESs) was synthesized and used as non-aqueous absorbents for the efficient absorption and recovery of HCl gas. It was found that the ChCl-Gly (1 : 1.5) DES exhibited high HCl absorption capacity (0.303 g g−1) at 298.2 K and 1.0 bar. In addition, the results of FTIR and 1H NMR spectroscopies revealed that the interaction of ChCl-Gly (1 : 1.5) with HCl was through hydrogen-bonding, demonstrating a high reversibility and recyclability of ChCl-Gly (1 : 1.5) DES in twenty cycles. The present study indicates that the ultilization of a ChCl-based non-aqueous absorbent is an effective methodology for the efficient absorption and recovery of HCl gas. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) have the advantages of low cost, non-toxicity, and biodegradability for the catalytic conversion of fructose to 5-hydroxymethylfurfural (5-HMF). However, the efficient separation of 5-HMF from DESs is essential and challenging for its high-value utilization. In this study, the efficient separation of 5-HMF from eight carboxylic acid-based DESs was achieved by four cycles of extraction using tetrahydrofuran (THF) with an overall extraction efficiency of more than 80.0% (30 °C). Besides, the addition of 1 mol L−1 NaCl solution can significantly improve the extraction efficiency from 30.0% to 42.0%. In addition, the process of recovery and reuse of the extractant was proved to be quite effective, in which the purity of 5-HMF in the recovered product and the amount of THF in the recycled extractant can reach up to 90.0% and 97.0%, respectively. Finally, a thorough procedure for the preparation, separation, and recovery of 5-HMF was carried out to assess the viability of the optimized separation and recovery process. The results reveal outstanding extraction efficiency (77.9%), excellent yield of 5-HMF (63.3%), and high purity of 5-HMF in the final product (86.0%). This work expands the range of possible uses for 5-HMF by demonstrating an efficient and environmentally friendly method for separating and recovering 5-HMF while ensuring the reuse of the extractant. [ABSTRACT FROM AUTHOR]

A novel biomass-derived magnetic nanocomposite of Fe3O4-Chitin@NADES-CC composed of a natural deep eutectic solvent (NADES), biological polysaccharide (Chitin) and magnetic Fe3O4 was synthesized. After being systematically characterized by Fourier transform infrared spectrometry, thermogravimetry, vibrating sample magnetometry, X-ray diffraction, transmission electron microscopy and dynamic light scattering, Fe3O4-Chitin@NADES-CC was used as an extractant to separate trypsin (Tryp) on the basis of magnetic solid phase extraction. Simultaneously, the extraction conditions of Fe3O4-Chitin@NADES-CC for Tryp were investigated in turn by single-factor experiments, including screening the types of extractants, the initial concentration of Tryp, the pH value of the solution, the influence of ionic strength, extraction time and temperature, etc. Under the optimal conditions, the extraction capacity of Fe3O4-Chitin@NADES-CC for Tryp could reach up to 1082.67 mg g−1. Adsorption isotherm tests certified that the Langmuir adsorption equilibrium fitted well with the extraction model in this study, which showed that the extraction of Fe3O4-Chitin@NADES-CC for Tryp was monolayer adsorption. In addition, in the sections on the regeneration–reuse, selectivity and methodological studies, all the results exhibited the superiority of the Fe3O4-Chitin@NADES-CC and Tryp separation strategy which has been established in this work. Finally, Fe3O4-Chitin@NADES-CC was ultimately applied to the separation of Tryp from a real bovine pancreas crude extract by the analysis of SDS-PAGE. All the above results highlight that the proposed Fe3O4-Chitin@NADES-CC biomass-derived magnetic nanocomposite can be applied in the field of protein purification. [ABSTRACT FROM AUTHOR]

Protection of amine groups by amide formation is still among the preferred strategies for multifunctional molecular synthesis despite its waste production, especially the enormous quantities of organic solvents used. In this study, we present a fast, cheap and eco-friendly method for amine group protection involving amide bond formation using choline chloride as a hydrogen bond acceptor and the starting amine as a hydrogen bond donor through the generation of "in situ" amine-based deep eutectic solvents. This novel approach avoids the use of toxic solvents, both during reaction and the work-up phase, thus representing a sustainable alternative to classic amine protection procedures. [ABSTRACT FROM AUTHOR]

Many studies have been focused on the selective separation of hydrogen chloride (HCl) gas, but its capture and conversion in situ is still at a standstill. Herein, a pioneering attempt to employ a deep eutectic solvent (DES) as a "courier" to combine HCl capture and in situ conversion has been presented. Impressively, the highest HCl absorption capacity is determined to be 3.95 mol/mol, or 0.672 g/g, or 18.4 mol kg-1 at 1.0 bar and 30 °C in a binary DES based on EmimCl/Im. The internal transmission mechanism between imidazole and HCl was revealed by DFT-based theoretical calculations. The reaction between HCl and epoxides achieved 99% conversion under mild conditions in the absence of a solvent, making the entire reaction ecologically benign. Water extraction was used to recycle the DES from the reaction system, and it maintained good catalytic performance after ten cycles. The exhaust HCl-SO2 mixed gases from the sucralose industry were further investigated, which proved the possibility of selective conversion of HCl. Furthermore, a plausible reaction-separation-integration (RSI) strategy was proposed to avoid the high energy consumption of desorption, which provides a novel insight into future applications. It is believed that the good results, combined with the simplicity of operation and the high recyclability of the catalyst, make this green method environmentally friendly and cost-effective. This work reveals an effective approach for the coupling of HCl capture and conversion under mild conditions. [ABSTRACT FROM AUTHOR]

The interactions between bovine serum albumin (BSA) and four lactic acid-based deep eutectic solvents (LADESs), namely lactic acid (LA): choline chloride (CC), LA: betaine, LA: polyethylene glycol (PEG), and LA: ZnCl2, were studied by spectroscopic and electrochemical methods under simulated physiological conditions. The binding constants, binding sites and quenching constants between the LADESs and BSA were calculated via measuring the fluorescence spectra and electrochemical curves at different temperatures, and the quenching type was determined to be static quenching. Through thermodynamic calculations and molecular docking, it was determined that the interaction forces between the LADESs and BSA are hydrogen bonds (H-bonds) and van der Waals (VdW) forces. According to Fōrster's theory, the energy transfer efficiency and the binding distance between the LADESs and BSA were calculated, and the quenching of fluorescence was attributed to the energy transfer. The binding rates of the BSA-LADES systems at different temperatures were calculated, and the ideal LADES extractant for BSA separation and purification was identified. Besides, the contents of the α-helix in BSA before and after its interaction with the LADESs were studied by circular dichroism (CD) spectroscopy. [ABSTRACT FROM AUTHOR]

The conversion of naturally occurring organic substances into value-added platform chemicals by simple, green, and efficient procedures represents one of the most accessible and sought-after routes towards sustainable chemistry. In the present work, we report the remarkable catalytic activity of rare-earth metal triflates in conjunction with choline chloride, a natural, low-cost, and available organic compound to selectively convert glucose and fructose into hydroxymethylfurfural (HMF). The hypothesized mechanism is based on the initial glycosylation of glucose assisted by scandium(III) triflate and choline chloride to produce a glycoside, which can evolve through an intramolecular rearrangement and subsequent dehydration to produce the final product HMF. A comparison with other types of catalysts is carried out with particular focus on the side reactions. The apparatus consists of a closed biphasic system and the excellent capacity of methyl propyl ketone (MPK) to extract HMF in only one cycle is proved. The process was conducted at 150 °C using 1.5 molar equivalents of choline chloride in which glucose was converted into HMF after three hours using the catalyst in 8% molar quantity, while fructose was converted in one hour employing the catalyst in 4% molar quantity. The best performance was obtained by employing scandium(III) triflate as a catalyst with an yield of 94% and 99% of HMF from glucose or fructose, respectively. We assumed a first-order reaction model for both glucose and fructose conversion into HMF. The R-squared values are greater than 0.9, demonstrating that our kinetic model fitted well with the experimental results. In addition, activation energies are 16.9 kJ mol−1 for glucose and 9.31 kJ mol−1 for fructose due to the longer reaction path of glucose. The catalytic system can be recycled up to five times with a HMF yield of over 80% for glucose and over 90% for fructose, maintaining the same selectivity. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DES) have received extensive attention in the extraction of natural products in the last few years. They are considered a substitute for conventional organic solvents because of their environmental advantages. To efficiently extract bioactive polyphenols and triterpenoids from the medicinal plant Celtis sinensis, fifteen DESs were prepared. The resulting DES1 (choline chloride-levulinic acid) showed the maximum extraction yield of total polyphenols, while DES9 (choline chloride-1,2-propylene glycol) had the maximum yield of total triterpenes. Further, the extraction conditions of DES1 and DES9 were methodically optimized. After optimizing the extraction conditions of DES1 and DES9, the extraction yield of total polyphenols was enhanced from 82.05 mg g−1 to 101.38 mg g−1 and that of total triterpenes from 57.87 mg g−1 to 72.72 mg g−1, both significantly superior to those of traditional water- and methanol-based extraction approaches. We designed a new DES by mixing DES1 and DES9 in the ratio of 7.25 : 2.75 to perform extraction of both polyphenols and triterpenes with high efficiency. The new DES solvent simultaneously increased the extraction yields of polyphenols and triterpenes to 118.46 mg g−1 and 88.51 mg g−1, respectively, after response surface methodology. More importantly, the extract obtained by the mixed solvent of DES1 and DES9 displayed significant antioxidant activity superior to those of extracts individually produced by DES1 and DES9. Our results indicate that a DES-based approach has promising potential in extracting bioactive substances from medicinal arbor species with high efficiency and eco-friendliness. [ABSTRACT FROM AUTHOR]

Multidisciplinary approaches are needed to overcome the various technical and technoeconomic challenges that have hindered the development of sustainable biorefineries. Herein, we report on the one-pot conversion of transgenic poplar biomass into bioproducts using biocompatible deep eutectic solvents (DESs). Engineered poplar wood with elevated levels of cell-wall-bound p-hydroxybenzoate (pHB) was processed using choline chloride–glycerol (ChCl–Gly) and betaine–glycerol (Bet–Gly), two non-conventional solvent systems. A metabolic engineering strategy that increased the abundance of terminal phenolic pHB groups on lignin resulted in transgenic poplar wood with reduced inherent recalcitrance. The engineered poplars, particularly those with the greatest levels of pHB, released more fermentable sugars and produced higher yields of bioethanol compared to wild-type trees following a one-pot treatment with ChCl–Gly. Equally important, the residual lignin was a rich source of alkylphenols upon hydrogenolysis, which highlights an important additional opportunity for lignin valorization. Our findings show how integrating plant cell wall engineering and process consolidation using biocompatible DESs could enable the development of sustainable biorefineries that effectively utilize both carbohydrates and lignin. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) have generated great interest as promising green alternatives to replace conventional solvents due to their application-specific tunability, nonflamability, variable viscosity, low vapor pressure, and chemical (and thermal) stability. However, their greenness or sustainability remains unclear and requires rigorous quantification. This work uses life-cycle assessment (LCA) to evaluate the potential environmental impacts incurred from the production of a representative choline chloride (ChCl)/urea DES, reline. The environmental profile of reline is compared with that of common organic solvents (methanol, ethanol, dichloromethane (DCM), and ethyl acetate) on the basis of their utilization as a solvent for the oxidation of alcohol to the ketone; acetophenone. The results indicate that, in general, the DES imparts lower environmental impacts than DCM and ethyl acetate but has higher impacts than methanol and ethanol. Chemical constituent materials (urea, trimethylamine, hydrochloric acid, and ethylene oxide) required for the synthesis of reline DES contribute significantly to its life-cycle environmental impacts when compared to auxiliary processes. In addition to reline, the LCA of four other ChCl-based DESs is performed by substituting urea (hydrogen bond donor in the reline) with ethylene glycol, glycerol, citric acid, or glucose. ChCl/citric acid DES, the so-called natural deep eutectic solvent, imposes the highest environmental impacts among the studied ChCl-based DESs. This is partly due to the high water consumption and carbon dioxide emission during fermentation to synthesize the citric acid. Our study challenges the greennesses of DESs but more research with better data is required to corroborate our findings as some key inputs were modeled from a commercial patent. [ABSTRACT FROM AUTHOR]

Nicotinamide adenine dinucleotide (NAD) coenzyme is a vital part of numerous enzymatic reactions that are involved in all major biological processes from energy metabolism to cell survival. Accordingly, it is used in a great number of biocatalytic reactions, as analytical biosensors, and in test kits for diagnostic and analytical purposes. This coenzyme is unstable in aqueous solutions, meaning that the minimization of its degradation during storage, assays, and enzyme-catalysed oxidoreductive reactions is of high importance. Herein, we report on the stabilisation of NAD (NAD+ as oxidised, and NADH as its reduced form) by deep eutectic solvents (DES), an emerging class of solvents that offer numerous remarkable advantages such as high tunability, and capability to stabilise a wide range of commercially important compounds of natural origin. Preliminary DES screening revealed that out of 7 candidates, choline chloride:urea (ChCl:U) shows the best ability to stabilise both NAD forms. Computational analysis (quantum chemical calculations and molecular dynamics simulations) provided a deeper insight into possible mechanisms behind the observed stabilisation, by identifying geometries and the solvation structure of NAD coenzymes in these solvents, and analysing their possible degradation pathways. Finally, prolonged NAD stability (up to 50 days) in ChCl:U is detected and the system is further confirmed as a stable working NAD solution in a model enzymatic assay. [ABSTRACT FROM AUTHOR]

Deep-eutectic solvents (DESs) are often considered to be safe, eco-friendly and non-toxic solvents. Due to these green credentials, they are increasingly being studied for application in metal recycling processes. One example is their use as lixiviants for the recovery of cobalt from lithium cobalt oxide (LiCoO2, LCO), which is a common cathode material in lithium-ion batteries. Here, leaching of cobalt is facilitated by reduction of cobalt(III) to cobalt(II) in the presence of a reducing agent. However, several recent publications report on the use of DESs as lixiviants at high temperatures (180 °C) without addition of a reducing agent. Typical DESs for these applications are based on mixtures of choline chloride and ethylene glycol (ChCl : EG). Unfortunately, these studies ignore the limited thermal stability of ChCl : EG at high temperatures, which limits the recyclability of this DES. In this work, the drawbacks of using ChCl : EG as the lixiviant in high-temperature ionometallurgical processes are demonstrated. Structural analysis confirmed that ChCl : EG is not stable at 180 °C, forming hazardous and toxic decomposition products such as trimethylamine and 2-chloroethanol. It was hypothesized that choline chloride reduces cobalt(III) while simultaneously undergoing a radical β-hydrogen abstraction reaction, thereby decomposing to trimethylamine and other degradation products. The main conclusion is that this type of DES should not be used for high-temperature leaching processes due to their limited stability under such conditions. [ABSTRACT FROM AUTHOR]

A new strategy has been proposed for synthesizing Co@CoO core–shell nanoparticles with a core–shell structure, which involves a facile solvent-thermal process in deep eutectic solvents (DESs). In contrast to the irregular sheet-like packing material obtained in water, twinned and 3D-ellipsoid-shaped nanoparticles were achieved in choline chloride (ChCl)/glycerol and ChCl/PEG-300, respectively. It was found that the nanoparticles were featured as metal Co(0) cores homogeneously wrapped by CoO shells after reduction under a H2 atmosphere. The Co@CoO core–shell nanoparticles showed good activity and stability for the hydroformylation of olefins, and the conversion of 1-octene can reach 99% at 130 °C under 4 MPa (CO/H2 = 1) pressure, and the selectivity to C9 aldehydes was reached up to 97%. The characterization by XPS, H2-TPR and HRTEM indicated that metal Co(0) species could be an active site for hydroformylation of olefins. Notably, the leaching of cobalt carbonyl species was highly dependent on the surface molar ratio of Co2+/Co0 as revealed by XPS spectra, and the surface CoO layer played an important role in suppressing the loss of active Co species in hydroformylation of olefins. Moreover, the core–shell nano-catalysts are easily separated magnetically from the reaction mixture and showed good recyclability in nine consecutive catalytic runs. [ABSTRACT FROM AUTHOR]

The integration of nanotechnology into lignocellulose biorefineries with multi-product outcomes is appealing but technically challenging due to lignin's random chemical structure. In this work, FeCl3- mediated deep eutectic solvents (DESs) were proposed to integrate microcapsulated pesticide production into current lignocellulose biorefineries to overcome this technical barrier. The addition of FeCl3 to choline chloride/lactic acid DES significantly enhanced hemicellulose removal (by nearly 100%) and lignin yield (62.1%). A high delignification ratio (70.8%) was obtained by FeCl3-mediated neutral DES (choline chloride/glycerol) pretreatment, which also significantly contributed to cellulose saccharification (81.6%). Moreover, an acid-catalyzed condensation reaction and the cleavage of β-O-4 linkages of lignin occurred during the FeCl3-mediated DES pretreatment. The condensation structure and abundant phenolic-OH content produced its special aromatic structure and enhanced the amphiphilic properties for the preparation of lignin nanospheres (LNSs), and further improved the anti-photolysis performance of LNS-encapsulated avermectin (AVM@LNS) pesticide. A strong positive correlation (R² = 0.86) between the phenolic- OH content and the half-life was also found. The tailored chemical structure of lignin also provided for its strong π-π stacking to promote nonradiative migration and trigger photothermal conversion. Unlike the bare AVM solution, AVM@LNS presented controlled release performance and temperature response behaviors for sustained pest control. This study achieved technical integration using the tailored lignin to realize the targeted downstream products, and also improved the high-value utilization of lignin by-products for green agriculture. [ABSTRACT FROM AUTHOR]

The growing environmental impact of non-renewable solvents has generated an increasing interest in the development of more sustainable alternatives. Among these options, deep eutectic solvents (DES) are attracting great interest. The favourable physicochemical properties of these solvents make them a potential green alternative for several applications. However, its toxicological impact has not been studied enough to assume the absence of environmental risk. With the main purpose of establishing an initial overview of the aquatic toxicity, an acute ecotoxicity test of different eutectic solvents, composed of glycerol or glycerol-derived ethers and choline chloride (ChCl) or N,N,N-triethyl-N-(2,3-dihydroxypropyl) ammonium chloride (N00Cl), has been carried out in two aquatic biomodels: Aliivibrio fischeri (bacteria) and Raphidocelis subcapitata (algae). Furthermore, the content of chlorophyll was measured to observe the disruption of the photosynthetic process by the tested compounds. A dose-effect correlation has been observed, although very high concentrations of the solvents were necessary for the onset of the toxic effect. The toxicity of the DES, within the ChCl case, turned out to be greatly related to the polarizability and hydrophobicity of the solvents. Whereas N00Cl-based DES have shown an even-odd trend, compounds with even carbon numbers in the ether radical show lower toxicity than odd ones. These preliminary results point out a favourable eco-toxicological behaviour of glycerol derived DES, although studies in other bioindicators, as well as in cells and biodegradability tests are recommended in order to have a complete overview of the toxicological profiles of these promising solvents. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) as promising green solvents can efficiently remove the lignin component in lignocellulosic biomass. Herein, novel ternary DESs formed by choline chloride (ChCl), thiourea dioxide (TD) and lactic acid (LA) were designed to efficiently dissolve the lignin and reduce the condensation reaction through the existence of a reductive microenvironment in fractionation processing. Compared to binary DESs (ChCl/LA), ternary DESs (ChCl/TD/LA) can efficiently reduce the condensation degree (DC) of lignin and improve the biological activity of lignin. Under optimum conditions (a DES ratio of 1 : 0.5 : 0.5, 130 1C and 4 h), the proportions of lignin and hemicellulose removed amounted to 69.77% and 47.71%, respectively. In addition, the hydroxyl (3.80--4.63 mmol g-1) and carboxyl (2.59--2.93 mmol g-1) contents of ternary DES lignin were higher than those of binary DES lignin, and the antioxidant activity (IC50 = 49.82--43.18 mmol L-1) was also better. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) are emerging as a new generation of sustainable and green media. Concerning the same, the present work outlines the synergistic information provided from the thermophysical assessment on new betaine hydrochloride (BHC)-based DESs. In order to acquire stable and convenient DESs, BHC as a hydrogen bond acceptor (HBA) is combined with urea (U) as a primary hydrogen bond donor (HBD) and ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), and glycerol (GLY) as secondary HBDs. A series of four different DESs, namely DES1 (BHC : U : EG), DES2 (BHC : U : DEG), DES3 (BHC : U : TEG), and DES4 (BHC : U : GLY) were optimized by a capricious molar ratio (1 : 4 : 2.5), which offers satisfactory liquid stability. Comprehensive spectral studies were used to investigate the molecular structure and the hydrogen bonding of the prepared DESs, while the important thermophysical properties viz., thermal stability (Tdec), density (ρ), speed of sound (u), viscosity (η), electric conductivity (κ), and refractive index (nD) were investigated at different temperatures. The effect of temperature on the measured thermophysical findings was correlated using a thermodynamic model. The viscoelastic and rheological findings revealed a considerable shift in the flow regime with varying HBDs in the prepared DESs. Furthermore, from an application viewpoint, these task-specific DESs were used for CO2 capture, where the outcomes indicated that DES2 (BHC : U : DEG) showed a high uptake of CO2 at 0.0200 mol of CO2/mol DES, which increased to 0.0319 mol of CO2/mol DES in DES2 in the presence of superbase (1,5-diazabicyclo[4.3.0]-non-5-ene (DBN)). Spectral studies indicated that CO2 reacts with the -NH2/-OH centers of DES via R–O–C＝OO−/–R–NH–C＝OO− formation during CO2 capture. Overall, the prepared DESs exhibit long-term performance in CO2 capture, which qualifies them as prospective and suitable alternatives to ILs. [ABSTRACT FROM AUTHOR]

New cellulose solvent based on choline hydroxide/urea (ChOH/Ur) deep eutectic solvent (DES) was developed. The ChOH/Ur DES has a promising solubility for cellulose compared to ChCl-based DESs. ChOH/Ur DES with ca. 11 wt% water can dissolve at least 9.5 wt% cellulose with the degree of polymerization (DP) of 926 within 30 min. Compared to the ionic liquids, the temperature window of ChOH/Ur is wide and close to room temperature. The ChOH/Ur DES also showed more tolerance to water than ionic liquid, which can save energy in preparation and usage. The physical and chemical properties of DES and cellulose solution were investigated. The ChOH/Ur DES system is a non-derivatizing solvent for cellulose. The preliminary rheological results suggest that the dynamics of cellulose solution in ChOH/Ur system is similar to that of salt-free polyelectrolyte solutions. The degradation of cellulose during the dissolution and storage of the cellulose solution is limited. After 7 days of storage at 40 °C, the DP of the regenerated cellulose remained at about 80% of the raw material. The ChOH/Ur is recyclable without the loss of solubility of cellulose. In conclusion, the ChOH/Ur DES system is a promising green solvent platform for preparing regenerated cellulose materials and could be used as a media for cellulose chemistry. [ABSTRACT FROM AUTHOR]

We report a catalyst-free pathway for the polymerization of furfuryl alcohol (FA) into poly(furfuryl alcohol) (PFA) using a deep eutectic solvent (DES) system. The DES prepared by mixing choline chloride (ChCl) and zinc chloride (ZnCl2) to polymerize FA in high yield under comparatively moderate reaction conditions. The FA conversion was found to increase with increasing reaction temperature and weight ratio of DES/FA. The highest yield of PFA (92.5%) was achieved at 80 °C in 4 h using a weight ratio of DES : FA of 10. FT-IR, 1H and 13C NMR, TGA, XRD and DSC analytical techniques were used to elucidate the structure and thermal behavior of the end product to confirm the successful formation of PFA. Moreover, we investigated the kinetics and calculated the activation energy for the reaction. A plausible mechanism for the reaction was proposed, focusing on the important role of the Ch+ cation to initiate the polymerization process. The main advantage of this work is the exploitation of DES systems as a recyclable medium that can efficiently catalyze FA polymerization without using any external solvent and catalyst. [ABSTRACT FROM AUTHOR]

ZnO mesocrystals have been explored for various physical and chemical applications. In spite of effort by a number of researchers, it is still difficult to grow specific crystal shapes in an environmentally-friendly, simple, and large-scale fabrication pathway. In this study, we report on a facile fabrication of ellipsoidal and double-cone-shaped ZnO mesocrystals elongated along the c-axis by an ionothermal method in choline chloride–urea deep eutectic solvents (CU-DESs) with addition of ethylene glycol (EG). It was found that as high as 16.7 mass% of ZnO could dissolve in CU-DESs at a high temperature by forming zinc cyanate complexes. Addition of EG to the above concentrated ZnO dissolved CU-DESs caused precipitation of ZnO particles which were confirmed as mesocrystals with transmission electron microscope images and selected area electron diffraction patterns. The crystal growth process and shape evolution in the CU-DESs were investigated and discussed. Photoluminescence study with excitation by ultraviolet light showed that the ZnO mesocrystals showed strong ultraviolet emission and relatively weak visible emissions, suggesting their high crystal quality. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is not only an important basic chemical raw material but also a typical polluting gas. The separation and recovery of NH3 from tail gas is of great significance for human health and the environment. In this study, a series of protic ionic liquid-based deep eutectic solvents (PIL-based DESs) were constructed by pairing imidazolium thiocyanate ([Im][SCN]) as the hydrogen-bond acceptor (HBA) with various hydrogen-bond donors (HBDs) [glycerol (Gly), ethylene glycol (EG), formamide (FM), acetamide (AT), and caprolactam (CL)]. Their physical properties and NH3 absorption performance were systematically investigated. The results showed that [Im][SCN] played a role in chemical NH3 absorption in the PIL-based DESs, while the HBDs mainly contributed to physical NH3 capture. HBDs containing hydroxyl groups demonstrated an evident improvement in NH3 absorption capacity compared to those with amide groups. [Im][SCN]–EG (1 : 3) demonstrated the highest mass capacity of 0.233 g NH3/g DES, which exceeded those of all the other IL-based DESs and originated from the multiple interactions between the acidic H as well as the hydroxyl groups in the DES and NH3, according to the 1H NMR and FTIR spectral analysis. Furthermore, [Im][SCN]–EG (1 : 3) indicated a high NH3/CO2 selectivity of 632.2, satisfactory thermal stability and excellent recyclability. [Im][SCN]–EG DESs possess great potential as attractive absorbents in NH3 separation and recovery. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DES) are attracting great attention as a green alternative to hazardous organic solvents for the extraction of valuable bioactive compounds from agricultural and processing waste. In this study, the simultaneous extraction and de-glycosylation of quercetin derivatives from apple pomace was achieved by using various DES made of choline chloride and different types of carboxylic acids. The content of quercetin derivatives was similar in DES and conventional methanol extracts, but their relative amounts were distinctively different due to de-glycosylation during DES extraction. Chromatographic and spectroscopic analyses allowed the determination of the structures of the glycosylated quercetins, and revealed that the proportion of the quercetin aglycon in DES extracts can be controlled by the DES composition, extraction temperature and duration of extraction. Of all quercetin glycoconjugates present, quercetin-3-O-α-arabinofuranoside was more prone to de-glycosylation during DES extraction than any other quercetin derivative. Furthermore, the antioxidant activity of the DES extracts was higher than that of methanol extracts, likely due to the increase of quercetin aglycon content during extraction. These data show the potential to extract and de-glycosylate quercetin derivatives in a single step using green DES to generate bioactive preparations with enhanced activity. [ABSTRACT FROM AUTHOR]

Poria cocos polysaccharides (PCPs) are of high research value because of their important biological functions. However, the ways to extract a PCP are limited and its yield is relatively low in current reports. In this study, a new ternary deep eutectic solvent (DES) composed of choline chloride, 1,3-butanediol and D -sorbitol was used to efficiently extract bioactive polysaccharides from poria cocos assisted by the new tool of far infrared radiation (FIR) together with hot air circulation (HAC). The yield of a polysaccharide (PCP-DL) obtained by this new method was 55.02 ± 0.87% under the optimized conditions of sieving mesh (300 mesh), liquid–solid ratio (30 mL g−1), intensity of FIR (300 W m−2), and circulated air temperature (80 °C). Meanwhile, the extraction mechanism of PCP-DL was investigated by comprehensive characterization studies and extraction kinetics. The recovered DES still retained its performance after recycling five times by dialysis. A laboratory-scale life cycle assessment (LCA) was applied to analyze the potential environmental profiles and the results showed that this new extraction process possessed environmental impact reductions of 93.61% waste solids and 69.72% fossil fuel depletion potential in contrast to the traditional method. Furthermore, chromatographic and spectral analyses were used to analyze the product and confirm the presence of α-,β-pyranose, as well as five kinds of glycosidic linkages, in target polysaccharides with a molecular weight (Mw) of 2.05 × 104 Da. Scanning electron microscopy (SEM) revealed that it was an amorphous aggregate with an irregular spherical shape and loose porous surface. Finally, the product exhibited a similar inhibitory activity to that of donepezil against acetylcholinesterase (AChE, 73.82 ± 0.60%) and butyrylcholinesterase (BChE, 63.85 ± 0.54%) at 500 μg mL−1 as a mixed-type competitive inhibitor for these enzymes. The interaction sites between AChE and the fragment of PCP-DL were simulated by molecular docking, which provided a theoretical basis for the above inhibition assays. [ABSTRACT FROM AUTHOR]

A new polymerizable and dynamic deep eutectic solvent (DES) consisting of choline chloride and α-lipoic acid is proposed. By virtue of thermally-initiated ring-opening polymerization (ROP) of cyclic disulfide and multiple dynamic interactions (disulfide, hydrogen, and coordination bonds), multifunctional ionogels with good comprehensive properties are developed and explored as potential flexible conductors. [ABSTRACT FROM AUTHOR]