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A highly efficient and sustainable approach was developed for the construction of Si–O/Si–Si bonds, through the electrochemical oxidative dehydrogenation of hydrosilanes with O-nucleophiles (e.g. phenols, naphthols, alcohols, and H2O) or hydrosilane self-condensation. The protocol employs a highly electrically conductive and recyclable ionic liquid as a catalyst, thus eliminating the need for external electrolytes and hydrogen atom transfer (HAT) agents. The ionic liquid could be easily recovered and reused for at least eight cycles with consistent performance. Notably, this electrochemical method exhibits a broad substrate scope and high functional-group compatibility (66 examples, up to 96% yield). Initial mechanistic studies show that silicon radicals are generated via the process of hydrogen atom transfer between bromine radicals and silanes, and KIE experiments demonstrate that Si–H bond cleavage is the rate-determining step of the reaction. [ABSTRACT FROM AUTHOR]

Over the past few years, the proliferation of lithium-ion batteries (LIBs) as pivotal energy storage solutions has surged dramatically. However, this widespread adoption has come with a significant downside: the accumulation of substantial quantities of discarded LIBs. From the perspective of green production and industrial development, the problem of recycling spent LIBs urgently needs to be addressed. Based on the physicochemical properties of ionic liquids (ILs) and deep eutectic solvents (DESs), as well as their potential in LIB recycling, this paper proposes the concept of the Ionic Liquid System, including ILs and DESs. The aim is to systematically outline the application of the Ionic Liquid System in the LIB recycling industry. Ionic Liquid System reagents are considered environmentally friendly green solvents due to their biodegradability. Here, we discuss laboratory research on the recovery of spent LIBs using similar system solvents based on studies reported over the past decade and categorize recent laboratory work, while evaluating the advantages and disadvantages of the application of the Ionic Liquid System. This article explicitly provides an effective reference for recycling spent LIBs through the Ionic Liquid System and prospects for future work on recycling spent lithium batteries. [ABSTRACT FROM AUTHOR]

Biodiesel, known as a renewable fuel, is an environmentally friendly energy source derived from animal and vegetable oils, as well as recycled oil. Despite this, the current advancements in biodiesel technology face challenges in fully replacing petrochemical diesel, primarily due to the non-green catalytic synthesis and high production cost associated with biodiesel. Ionic liquids containing strong Lewis acids or Brønsted acids have been highlighted as a novel class of environmentally friendly solvents and catalysts, showing green and effective catalytic potential in the synthesis of biodiesel via transesterification. In another aspect, reactive distillation technology could facilitate continuous forward reactions catalyzed by ionic liquids by swiftly removing reaction products from the reaction zone, offering advantages in improving the production efficiency, energy consumption, and cost reduction. From this perspective, we discuss the synthesis of biodiesel catalyzed by ionic liquids, supported ionic liquids, amphiphilic ionic liquids, and amphiphilic supported ionic liquids. The focus is on the process for synthesizing biodiesel through catalytic distillation. We emphasize the potential role of the lipophilic group in the ionic liquid catalyst, promoting the mutual solubility of the reactant triglyceride with methanol or ethanol. This enhancement might facilitate contact between the reactants and improve the catalytic efficiency of transesterification. Additionally, we propose several methods to improve the efficiency of biodiesel synthesis catalyzed by ionic liquid catalysts and suggest appropriate reactive distillation processes for biodiesel production. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) are increasingly used, e.g. as solvents, electrolytes, active pharmaceutical ingredients and herbicides. If ILs enter the environment due to their use or accidental spills at industry sites, they can pollute the environment. To avoid adverse side effects of persistent ILs in the environment, they should be designed to fully mineralise in the environment after they fulfilled their function during application. (Quantitative) structure–biodegradability relationship models ((Q)SBRs) have been successfully applied in the design of benign chemicals. However, (Q)SBR models have not been widely applied to design mineralising ILs. Therefore, in this study we developed five quantitative structure–biodegradability relationship (QSBR) models based on OECD 301D data from the literature and our own in-house biodegradation experiments. These models can potentially be part of a test battery for designing fully mineralising ILs to increase the overall reliability of the biodegradability assessment and reduce uncertainties. Two datasets were formed and randomly divided into a training set with 233 and 321 compounds and a test set with 26 and 36 compounds, respectively. Both classification and regression models were built using molecular fragments with the aim to predict the classification and continuous biodegradation rate, respectively. The internal and external validations produced a R2 of 0.620–0.854 for the regression models and accuracy, true positive rate, and true negative rate were between 62 and 100% for the classification models indicating an adequate performance but also a need for improvement. For the models and the test battery presented in this study, further research is needed to demonstrate their applicability. [ABSTRACT FROM AUTHOR]

Recently, poly(ionic liquid)s (PILs) have emerged as a family of polymeric materials which are being increasingly investigated for interdisciplinary applications. Their high electrical conductivity, excellent thermal/mechanical stability, low vapor pressure, and easy processibility render PILs exceptionally attractive as versatile platforms for green chemistry. Recent decades have witnessed fruitful efforts devoted to the development of PIL-based green chemistry platforms, achieving significant discoveries that will unfold their uniqueness in catalysis, separation, sensors, electrolyte, and functional materials. However, few review papers offer comprehensive discussion on PILs' application in the green chemistry field. In this review, we initially introduce the structure and types of PILs, which is followed by a systematical summary of the synthesis of PILs in terms of direct polymerization of monomer, polymerization after monomer modification, and modification of polymers. Furthermore, several aspects of the application of PILs related to green chemistry are highlighted, such as sensors, separation, catalysis, electrolytes for energy storage devices, and as versatile precursors yielding functional materials. Current challenges and corresponding research directions in PILs for green chemistry are clarified, to make PILs truly green platforms for existing technologies. [ABSTRACT FROM AUTHOR]

Herein, an ionic liquid, 1-[1-(ethoxycarbonyl)-2-oxopropyl]-3-methylimidazolium chloride (1,3-(CO)2IL-HCl), was synthesized and used as a donor of hydrogen chloride (HCl) to participate in an organic reaction. Interestingly, the simultaneously generated 1-[1-(ethoxycarbonyl)-2-oxopropyl]-3-methylimidazolium inner salt (1,3-(CO)2IL) can then capture HCl from another reaction that produces HCl as a waste. This allowed us to use IL as a shuttle to transfer waste HCl from the first reaction to the second one that needs HCl as one of the reactants. In a proof-of-concept experiment, a ring-opening reaction of glycidyl phenyl ether with released HCl was selected; and the waste HCl comes from an alcoholysis of benzoyl chloride with ethanol. 1,3-(CO)2IL can be used as a shuttle for transferring HCl five times without evident decline of its performance. Mechanism investigation revealed that the interconversion of keto and enol forms in 1,3-(CO)2IL and a moderate pKa value are keys to ensuring the release and capture of HCl. [ABSTRACT FROM AUTHOR]

The fundamental requirements of self-powered hydrogels used in flexible electronic products encompass excellent mechanical performance and conductivity. However, simultaneously achieving high performance in both the aspects remains a great challenge during the fabrication of self-powered hydrogels. In this study, robust and recyclable self-powered polysaccharide-reinforced polyvinyl alcohol (PVA) networks were established by modulating ionic channels using Zn2+/Li+ bimetallic salt solutions. The results indicate that the hydrogel equilibrated in a bimetallic salt solution of 1 M concentration can simultaneously achieve an impressive tensile strength of 1.36 MPa and an optimal ionic conductivity of 1.64 S m−1 since carboxyl groups on the polysaccharide chains enable the adsorption of more metal ions without restricting ionic mobility as a result of higher conductivity. By leveraging their excellent electrochemical performance, conductive hydrogels can serve not only as flexible sensing materials with enhanced sensitivity to monitor human motion and facilitate information transmission, but also as recyclable electrolytes in self-powered hydrogel batteries. Interestingly, self-powered hydrogel batteries can maintain a stable voltage of 0.82 V and show good recyclability, which can restore the original voltage output via a simple salt solution equilibration method, offering significant potential in applications such as wilderness survival. This work provides a novel strategy for the rapid and green preparation of robust, recyclable, and self-powered polysaccharide-based hydrogels. [ABSTRACT FROM AUTHOR]

Paclitaxel (PTX) is a crucial medication employed in the treatment of various cancers, and its limited solubility has been a persistent clinical hurdle. Ionic liquids (ILs), considered as "green solvents", possess remarkable attributes such as exceptional miscibility, tailorable properties, and versatility. These properties have ushered in a revolution in the realm of biomedicine, particularly in addressing the solubility challenges of poorly soluble drugs. In this work, low-toxicity diimidazolium based ILs were introduced into a PTX dissolution system for the first time. Compared to mono-imidazolium based ILs, diimidazolium based ILs exhibited lower in vitro cytotoxicity and the substitution of Cremophor EL (CrEL) with biocompatible [C10(MIM)2][Br]2 and water resulted in lower cytotoxicity at a certain concentration. Furthermore, [C10(MIM)2][Br]2 could effectively improve the solubility of PTX, and this enhancement was strongly correlated with the length of the carbon chain in the cation and the IL concentration. Significantly, the [C10(MIM)2][Br]2-based dissolution system demonstrated the capability to attain a PTX content that is on par with the widely used commercial drug Taxol. Besides, the [C10(MIM)2][Br]2-PTX complex displayed excellent physical stability for a long period of time, with no significant change of PTX concentration in the solution. Additionally, various interactions existed between [C10(MIM)2][Br]2 and PTX, encompassing hydrophobic interactions, p-p stacking, CH-p interactions, and hydrogen bonds. The results indicated that the diimidazolium based IL system showed promise as a biocompatible platform for the delivery of PTX. [ABSTRACT FROM AUTHOR]

Chemical upcycling of plastic waste has garnered global attention due to its sustainable approach to addressing the growing plastic waste accumulation problem and facilitating the establishment of a circular plastic economy. Methanolysis is a chemical upcycling process for the depolymerization of post-consumer polycarbonates and polyesters into their monomeric feedstock, which generally requires an excess amount of co-solvents and homogeneous inorganic salts. Herein, a solvent-free heterogeneous catalytic chemical upcycling of poly(bisphenol A carbonate) (BPA-PC) and poly(lactic Acid) (PLA) is proposed for the production of bisphenol A (BPA) and methyl lactate (ML) with a high yield using SBA-15 functionalized basic ionic liquid catalysts. Among all the synthesized catalysts, SBA-15-Pr-MIM-OH exhibited the highest basicity and demonstrated the best performance for depolymerization of PC and PLA at 120 °C, completing the reaction in 1 h and 4 h, respectively, with a complete conversion and a monomer yield of >98%. The reaction condition was optimized to get the best catalytic performance and product selectivity. Furthermore, the "one-pot" depolymerization strategy was applied for the chemical upcycling of mixed plastic waste (BPA-PC/and PLA) to their monomers. A detailed depolymerization pathway is provided, supported by FT-IR spectroscopy, 1H NMR spectroscopy, and TGA. The parameters for green chemistry metrics were evaluated to show the efficiency and sustainability of the proposed system, opening doors for the industrial upscaling of plastic depolymerization. [ABSTRACT FROM AUTHOR]

A practical electrochemical strategy for the direct synthesis of arenesulfonyl fluorides from industrial feedstock nitroarenes is described. The key to success lies in using a cheap ionic liquid N-methylimidazolium p-toluenesulfonate ([Mim]TolSO3) as an effective additive and electrolyte to facilitate the selective reduction of nitroarenes to the corresponding aniline intermediate, promoting the desired fluorosulfonylation with broad functional group tolerance under mild conditions. [ABSTRACT FROM AUTHOR]

The biorenewable carbohydrate-derived rigid building block of isosorbide (ISB) has demonstrated potential in high-performance polymer materials; however, a controllable eco-friendly preparation technology is not yet available. For this purpose, a sustainable strategy to synthesize ISB-based polycarbonate (PIC) has been established by adopting the CO2-based compound dimethyl carbonate (DMC) as a monomer and ionic liquids (ILs) as metal-free catalysts. The molecular weight of PICs can be readily controlled by varying the cation structure of IL catalysts. Control experiments, density functional theory (DFT) calculations, and Kamlet–Taft solvent parameters indicated that the H-bond donor/acceptor (HBD/HBA) ability of IL catalysts played a dominant role in regulating catalytic activity. PIC molecular weight can be modulated by modifying the inherent difference in reactivity of endo-OH and exo-OH in ISB, wherein the chain length or substituent group of cations can regulate the HBD/HBA ability of IL catalysts and anions can specifically activate the carbonyl carbon of DMC. The experimental results revealed that a task-specific [Pmim][OAc] catalyst exhibited the highest catalytic activity, which is attributed to its significant role in considerably lowering the disparity in reactivity between endo-OH and exo-OH. For this DMC route, the [Pmim][OAc] catalyst offered a PIC with the highest molecular weight of 57 200 g mol−1 reported to date. Furthermore, a well-supported polymerization mechanism was proposed, in which [Rmim][OAc]'s anion–cation synergistically catalyzed ISB and DMC to prepare PIC. Our findings offer a clear pathway for designing efficient metal-free catalysts to enable the sustainable synthesis of high molecular weight PICs, thus expediting the industrialization of the DMC route. [ABSTRACT FROM AUTHOR]

This review provides an overview of the current state-of-the-art and major trends in the application of protic ionic liquids (PILs) to sustainable chemistry. Following a brief description of the distinguishing properties of PILs, there are four application areas reviewed: acid catalysis, biomass transformations, energy storage and conversion, and electrocatalysis. The aim of this contribution is to showcase applications in which the properties of PILs are the key enabling factor for a particular sustainable chemistry challenge. In addition, the challenges and future directions in sustainable applications of PILs are discussed, highlighting challenges as well as areas for future development. [ABSTRACT FROM AUTHOR]

The dissolution of chitosan is a tedious and time-consuming process. Herein, we select the best Ionic Liquids (ILs) for chitosan dissolution through the application of Conductor-like Screening Model for Real Solvents (COSMO-RS), which allowed the screening of 640 ILs based on 32 cations based on amino acids, imidazolium, pyridinium, and pyrrolidinium, and 20 selected anions such as [C2H3O2], [Cl], [NO3], [BF4], and others. Thermodynamic properties such as logarithmic activity coefficient at infinite dilution (ln γ) and excess enthalpy (HE) were used to evaluate the dissolution potential of ILs towards chitosan, whereby low values of ln γ and HE indicated better engagement between the solute and the solvent, thus resulting in a higher solute being dissolved. A preliminary screening of chitosan dissolution was carried out in all 5 synthesized ILs to validate the results obtained by COSMO-RS. It was observed that ILs with [BF4−] as the anion and cations such as [Ser], [Gly], [Phe], [Cys], and [Asn] have the lowest ln γ values, hence better interaction with chitosan. The values of HE indicated that the molecular interactions between chitosan and ILs were governed by hydrogen bonding (ranging from 37 to 50%), followed by misfit interactions (ranging from 21 to 31%) and van der Waals forces (ranging from 22 to 32%) due to the abundance of hydroxyl (–OH) groups present in the intermolecular and intramolecular chitosan structures. These proved the great ability of COSMO-RS to accurately predict the dissolution of chitosan in ILs. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) are emerging as promising materials for the separation of heavy metals from complex feed streams through selective complexation. A predictive understanding of the coordination chemistry between ILs and targeted metal ions is critically important for enabling the rational design of efficient and selective separations. Such understanding is challenging to obtain due to the labile nature of the bonds and complicated structures formed by ILs in solution. Herein, we elucidated the complex formation of imidazolium-based ILs (i.e., 1-ethyl-3-methylimidazolium chloride, EMIMCl) with lead cations (Pb2+) in both the gas and aqueous phases employing a combination of experimental and theoretical methods. Gas-phase electrospray ionization mass spectrometry (ESI-MS) and negative ion photoelectron spectroscopy (NIPES) experiments suggest that Pb–Cl anions (e.g., PbCl3− and Pb2Cl5−) combine with neutral EMIMCl molecules, forming complexes of [PbmCl2m+1][EMIMCl]n− (m = 1, 2, n = 1–4). These anionic complexes are shown to become less stable toward fragmentation and require more energy to dissociate an electron with an increasing number of EMIMCl molecules. In contrast, in dilute solutions, dissociated EMIM+ cations and Cl− anions give rise to electrostatic screening of Pb–Cl bonds, resulting in the formation of distinct condensed phase complexes, such as [PbCl5][EMIM]2. These structures were identified by nuclear magnetic resonance (NMR) spectroscopy coupled with density functional theory (DFT) calculations. The energy gap between the highest occupied and lowest unoccupied molecular orbitals (HOMO–LUMO) of the condensed phase complexes containing EMIM+ was calculated to be lower compared to the Pb–Cl ionic clusters without IL, making these species more electrochemically reducible and easier to extract from solution. This study emphasizes the importance of understanding complexation between ILs and metal ions in designing efficient separation methods. [ABSTRACT FROM AUTHOR]

Lignin is an amorphous, heterogeneous, aromatic biopolymer that is obtained from nature. The scientific community is very interested in how lignin might be converted into compounds with added value in order to support a sustainable future and biobased economy. Ionic liquids (ILs) and deep eutectic solvents (DESs) are emerging as important kinds of comparatively greener solvents, and have been used for the catalytic transformation of different kinds of lignin and its model compounds into a wide variety of useful chemicals. The catalytic transformation processes can be carried out more quickly and possibly with less negative environmental effects by utilizing the unique qualities of these green solvents (ILs and DESs) with various functions. Catalytic systems that use ILs and DESs as media or catalysts may also yield a new product line. The catalytic chemical conversion of lignin to value-added chemicals and fuel products using ILs and DESs as reaction medium is the subject of this review. Several studies have been carried out on lignin solubility and extraction using these solvents; therefore, herein we have reviewed the advances in lignin valorization to fine chemicals using ILs and DESs. [ABSTRACT FROM AUTHOR]

Millions of tons of solvents are consumed annually in various industrial sectors, such as pharmaceuticals, chemical synthesis, textiles, coatings, paints, and others. Ionic liquids (ILs) are pairs of ions in the liquid form synthesized at temperatures below 100 °C that meet specific demands of processes, replacing organic solvents that are harmful to the environment. They offer exceptional prospects as advanced solvents owing to their unique attributes and remarkable recyclability. However, alkyl imidazolium-based ILs have proven to be flammable when exposed to heat, and cytotoxicity and phytotoxicity were observed for many traditional ILs. Therefore, with a focus on negligible toxicity, biocompatibility, straightforward preparation, and sustainability, biocompatible ionic liquids (Bio-ILs) have emerged with huge potential in many different fields of chemistry. These solvents are specifically designed to be derived from naturally occurring compounds. Their physical–chemical properties, modulated according to the application, make them an attractive green technology. Therefore, this review addresses the recent advances in Bio-ILs that include the production of renewable commodities and approaches in catalysis and the pharmaceutical field. Likewise, patents and future perspectives are discussed, demonstrating the great potential of Bio-ILs as green and sustainable compounds. [ABSTRACT FROM AUTHOR]

The separation of structurally similar compounds, such as cholic acid (CA) and deoxycholic acid (DCA), is challenging due to their nearly identical physicochemical properties. This study demonstrates a synergistic 'push and pull' strategy with an ionic liquid (IL) biphasic system for significantly enhanced CA/DCA separation efficiency. Ethyl acetate was selected as the feed solvent to 'push' CA into the IL-rich extractant phase, while the IL 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) was chosen to 'pull' CA due to their strong hydrogen bonding interaction. This 'push and pull' system yielded a remarkable CA/DCA selectivity up to 47.8, much higher than the case using n-butanol which pulls both CA and DCA. The underlying separation mechanism was elucidated through computational screening with COSMO-RS, NMR analysis, and solvatochromic measurements. Results revealed the critical roles of specific hydrogen bonding between the chloride anion of [EMIM]Cl and the hydroxyl/carboxyl groups of CA/DCA, along with nonspecific interactions between the feed solvent and CA/DCA. Thermodynamic analysis of the phase transfer process confirmed the 'push and pull' synergy is energetically favorable for preferentially transferring CA from the ethyl acetate feed solution into the IL-rich extractant phase. Multi-stage simulation indicated that 99% purity and recovery of both CA and DCA can be obtained through this biphasic system under optimized conditions. Overall, strategically tuning both the feed solvent and IL extractant could significantly enhance the separation efficiency of structurally similar compounds while minimizing solvent and energy consumption. This 'push and pull' approach may shed light on improving separation processes for other structural analogues. [ABSTRACT FROM AUTHOR]

The development of highly efficient and environmentally friendly solvents for dissolving cellulose, which is the most abundant natural polymer on Earth, remains a challenge, hindering its full utilization. Herein, a green protic ionic liquid, 1,1,3,3-tetramethylguanidinium methoxyacetate ([TMGH][MAA]), was found to exhibit attractive capacity to dissolve natural cellulose with an appropriate TMG/MAA molar ratio of 7 : 3 at 80 °C. The solubility of cotton linter and ultra-high molecular weight cotton fibers reached 13% (w/w) and 3% (w/w), respectively, surpassing that of most solvent systems currently used for the dissolution of cellulose. The experimental and simulation results verified that the excellent dissolution ability of [TMGH][MAA] for cellulose is mainly attributed to the destruction of the intrinsic hydrogen-bond networks in cellulose by the synergistic interactions of the [TMGH] cations and [MAA] anions with the hydroxyl groups in the cellulose chains, acting as highly efficient "intermolecular scissors". The superiority of this novel dissolution system was further demonstrated by the remarkable comprehensive properties of the regenerated cellulose film including satisfactory thermostability, high transparency, and excellent mechanical properties. Furthermore, the satisfactory recovery performance of this solvent highlights its significant feasibility for large-scale industrial manufacturing. The proposed [TMGH][MAA] in this study exhibits great potential as a next-generation processing solvent for dissolving, and thus processing cellulose, promoting the sustainable development of high-value-added cellulose materials. [ABSTRACT FROM AUTHOR]

Environmentally open applications as herbicides or active pharmaceutical ingredients are discussed for ionic liquids (ILs). Since most of the ILs are not readily biodegradable in the environment, they may persist there. To prevent the accumulation of persistent and toxic ILs, both the cation and anion need to be designed to completely mineralise in the environment. Several studies summarised structure–biodegradability relationships (SBRs) and gained rules of thumb for ILs' biodegradability based on the available literature data. However, no study systematically analysed a dataset using an in silico tool. Therefore, to identify SBRs a dataset on the ready biodegradability of 508 ILs was clustered according to IL similarity by using the software Canvas by Schrödinger. The biodegradability was divided into three classes (biodegradation rates 0–19%, 20–59% and ≥60%). The identified SBRs were compared with the available rules of thumb from the literature. The results show that the cholinium cation and its derivatives acetylcholine, betaine and carnitine are promising candidates for designing environmentally mineralising ILs if a good biodegradable anion is chosen. Imidazolium and phosphonium ILs should be avoided. For pyrrolidinium and quaternary ammonium compounds cations containing ester or carboxyl groups in side chains and alkylsulphate anions should be tested to close gaps in SBRs and possibly design a mineralising IL. Due to the limited data of morpholinium, 1,4-diazabicyclo[2.2.2]octanium (DABCO), piperidinium, prolinium, piperazinium and thiazolium ILs, SBRs could not be clearly identified. Further research is needed on whether structural adjustments according to the findings can increase the biodegradability of not yet fully degrading (20–59%) ILs. [ABSTRACT FROM AUTHOR]

The purpose of this short perspective review is to summarize the recent literature on the main trends in the use of polymer ionic liquids (PILs) published in the period from 2021 to 2023. Only the most promising areas that will play crucial roles in the very near future are considered. These areas include, in the authors' opinion, the biochemical and medical applications of PILs; sorption and separation of gases and liquid-phase sorption; solar cells; chemical sensors, supercapacitors and polymer transistors; and catalysts (including electro- and photocatalysts). The advantages of and approaches for improving the efficiency as well as the green approach for the synthesis and use of PILs are discussed. [ABSTRACT FROM AUTHOR]

Ring-closing metathesis (RCM) reactions of multiple bonds have seen considerable progress; however, RCM reactions involving single bonds, especially two different single bonds are scarce and extremely challenging. Herein, we present a cation–anion confined hydrogen bonding catalysis strategy for catalyzing the ring-closing C–O/O–H metathesis of alkoxy alcohols to O-heterocycles under metal-free conditions. Assisted with theoretical computation, the effective ionic liquid catalysts were first predicted. [HO-EtMIm][OTf] was found to display the highest activity, consistent with the predicted results. This catalyst could afford a series of O-heterocycles, including tetrahydrofurans, tetrahydropyrans, dioxanes, and some complex ethers that are difficult to access via conventional routes. Moreover, it was recyclable and reusable without activity loss after 5 recycles. Comprehensive investigations endorse that [HO-EtMIm]+ cation and [OTf]− anion selectively form hydrogen bonds with the ether O atom and hydroxyl H atom of alkoxy alcohol in opposite directions, respectively, which cooperatively catalyze the reaction in the cation–anion confined ionic microenvironment. The strategy presented here provides a novel and green route to access cyclic ethers. [ABSTRACT FROM AUTHOR]

Despite the enormous potential of zinc metal as an anode material for cost-competitive and safer power sources, the practical application of aqueous zinc batteries (AZIBs) has been plagued by uncontrollable detrimental side reactions and dendrite growth. To tackle these challenges, we propose a novel design strategy that focuses on balancing the hydrophobicity and zincophilicity of poly(ionic liquid) (PIL) solid–electrolyte interphases (SEIs). PILs with the same cation ([VBIm]+) but different anions (BF4−, TFO−, TFSI−) were polymerized on Zn electrodes to form artificial SEI layers with adjustable hydrophobicity. The hydrophobicity of the PIL SEIs leads to the formation of a uniform surface, which is beneficial for eliminating dendrites and inhibiting side reactions. As a result, the Zn‖[PVBIm][TFSI]@Ti cell exhibits a significantly improved coulombic efficiency of 99.61%. Nevertheless, it is important to note that the enhanced hydrophobicity, which contributes to benefits such as better coulombic efficiency, also introduces an inevitable risk of compromised zinc kinetics. To address this trade-off, a zwitterionic PIL, [PVIPS][Zn(TFSI)2], with a zincophilicity group (–SO3−) was proposed. This approach substantially improves the reversibility and long-term stability of Zn anodes, as evidenced by the outstanding capacity retention of the [PVIPS][Zn(TFSI)2]@Zn‖PANI full cell (81.32% after 2000 cycles) and 13 times longer life of symmetrical cells (over 1950 h at 1.0 mA cm−2/1.0 mA h cm−2) compared to bare Zn symmetrical cells. [ABSTRACT FROM AUTHOR]

Developing a simple and efficient heterogeneous catalyst for the cycloaddition of epoxides with CO2 under atmospheric pressure and cocatalyst-/metal-/solvent-free conditions remains a great challenge. Herein, poly(ionic liquid)s (P-[VRIm]Br-crosslinker-x) with unique adsorption-swelling ability toward epoxides are designed and facilely synthesized via free radical polymerization in water. The adsorption-swelling of epoxides by P-[VRIm]Br-crosslinker-x is controllable, reversible, and widespread, resulting from the strong interactions between the poly(ionic liquid)s and epoxide molecules, especially the hydrogenbonding interaction. Superior CO2 cycloaddition is realized in the P-[VRIm]Br-crosslinker-x catalyst through the adsorption-swelling effect. Specifically, P-[VC6Im]Br-C8-5% with 54.1 mmol g-1 adsorptionswelling ability toward styrene oxide achieves 89.3% yield and >99% selectivity in the cycloaddition of styrene oxide with CO2 to styrene carbonate under mild conditions (1 atm, 80 °C) without cocatalyst/metal/solvent consumption. Moreover, P-[VC6Im]Br-C8-5% can be easily recovered by deswelling, and shows good reusability and stability after five cycles for a total of 180 h. The adsorption-swelling property of P-[VRIm]Br-crosslinker-x to epoxides not only prompts the active centers to be fully exposed to the reactants but also induces the enrichment of epoxides during the whole catalytic process, thus accelerating the CO2 cycloaddition reaction rate. This work furnishes new insights for improving the activity of CO2 cycloaddition and would guide the design of efficient poly(ionic liquid) catalysts for atmospheric CO2 conversion. [ABSTRACT FROM AUTHOR]

When we look for a poster child of green chemistry 'in action', we do not need to look further than the deconstruction of lignocellulose using ionic liquids (IL) to valorize this renewable resource into useful chemicals. However, there is a caveat: successful development of new chemistries cannot be achieved without systems-based design tools that consider performance in conjunction with potential toxicity. Here, we show that a combination of computational approaches, based on quantum mechanics (QM) calculations and Monte Carlo (MC) simulations, can be leveraged to construct a useful framework for screening existing and designing new ILs capable of safe and selective dissolution of lignocellulosic biomass. With the overwhelming number of IL cation–anion combinations, in silico methods are uniquely suited for this challenge so long as they retain mechanistic relevance to the underlying processes. Our computational approach ensures this criterion by relying on well-correlated linear models of interaction energetics between IL and key biomass building blocks. Functional considerations are supplemented with frontier molecular orbital calculations to determine safety toward aquatic species based on previously established and broadly validated guidelines. [ABSTRACT FROM AUTHOR]

A new homogenous silylation method of cellulose is developed by mixing it with monohydrosilane in an ionic liquid. In this concise reaction with high atom economy, the ionic liquid acts as both the solvent and catalyst, and the only formal by-product generated is the clean fuel of molecular hydrogen. [ABSTRACT FROM AUTHOR]

A waste-free chemical process involving comparatively greener solvents with recyclability is one of the desired goals of sustainable development. In this regard, task-specific ionic liquids (TSILs) emerge as groundbreaking solution, acting as both eco-friendly catalysts and reusable solvents in numerous industrial reactions. Herein, we exemplify the use of a family of phosphorus anion-based ionic liquids (ILs) having alkyl ammonium, pyridinium or lutidinium cations for successful isomerization of α-pinene oxide (APO) to industrially applicable trans-carveol with 74% selectivity and 99% conversion. This is the first time that we achieved isomerization of α-pinene oxide (APO) to trans-carveol with a very high selectivity as compared to campholeneic aldehyde in ionic liquid media. The mechanism for this conversion is well correlated with the physical properties (conductivity, density, molecular volume, standard entropy, and lattice energy) of the synthesized ionic liquids. The derived parameters from primary physical properties and Kamlet–Taft parameters provide strong support for greater reactivity and selectivity. The synthesized TSILs are chemically stable, easy to separate, and reusable for multiple runs without compromising the conversion of PO. The designed process fulfils the green metrics criteria by having 100% atom economy with an E-factor of 1. [ABSTRACT FROM AUTHOR]

Herein, a novel class of room temperature chiral phosphine-functionalized polyether imidazolium ionic liquids (RTCP-PolyIMILs) was synthesized for the first time by an ion exchange reaction between the 5,5′-disulfonato-(S)-BINAP ligand and polyether imidazolium ILs. The interactions with the polyether imidazolium transformed the solid sulfonated BINAP with a high melting point into a room temperature IL, which can act as a phosphine ligand and a carrier. Using the attractive dual functionality of RTCP-PolyIMILs, an efficient and sustainable homogeneous catalysis and biphasic separation system (HCBS) was constructed for Ru(II)-catalyzed enantioselective hydrogenation of β-keto esters to optically active β-hydroxy esters. Only a catalytic amount of RTCP-PolyIMIL was needed in the absence of any external carrier ILs, allowing the easy recovery and recycling of the chiral Ru catalyst. The Ru(II)-RTCP-PolyIMIL catalyst showed higher activity and better adaptability to a wide range of solvents than the traditional Ru(II)-BINAP catalyst. Specifically, a TOF value of up to 3900 h−1, an enantioselectivity of up to 99%, long-term stability up to a total TON value of nearly 17 000, an extremely low Ru loss rate of only 0.08–0.09%, and good universality for structurally diverse β-keto esters with different electronic and steric properties were demonstrated. These dramatic enhancing effects can be attributed to the structure of RTCP-PolyIMILs integrated with a phosphine ligand and polyether ILs, where polyether-induced clustering blocking-up and polarity enhancement effects played critical roles. [ABSTRACT FROM AUTHOR]

Ionic liquid-based membranes (ILMs) have garnered significant attention due to the unique coordination properties offered by both ILs and membranes. This makes them a promising area of research with a wide range of potential applications. In recent years, there has been a surge of exciting research activities in the field of ILMs in liquid separation, ranging from fabrication strategies to the development of separation applications. In this review, targeting different types of ILMs, i.e., supported ionic liquid membranes (SILMs), ionic liquid-polymer membranes (ILPMs), poly(ionic liquid) membranes (PILMs), and ionic liquid polymer inclusion membranes (ILPIMs), the preparation strategy, applicability, stability, transport mechanism, and future perspectives are summarized. By providing a comprehensive overview of the different types of ILMs and their applications in liquid separation, this review aims to serve as a valuable resource for researchers and engineers seeking to develop new-type and innovative ILMs for specific separation tasks. It highlights the advantages and limitations of each type of ILMs as well as the various preparation strategies and performance criteria used to evaluate their effectiveness. Ultimately, this information is expected to guide the design and optimization of novel advanced ILMs with enhanced functional properties for real-world applications. [ABSTRACT FROM AUTHOR]

To reduce the emission of NO from fossil fuel combustion and the energy consumption associated with NH3 production, the development of simple and efficient methods to transform NO into high-value-added NH3 is essential. Here, we report the efficient catalytic hydrogenation of NO to NH3 under mild reaction conditions by the synergistic catalysis of functionalized ionic liquids (FILs) and Pd catalysts. In this system, an FIL [TEPA][Im] acted as both an absorbent and a catalyst. The presence of [TEPA][Im] enhanced the catalytic performance by changing the coordination and electronic environment of Pd on the Pd/C catalyst. First, NO was absorbed by [TEPA][Im]; then, the hydrogenation of absorbed NO to NH3 was performed at a low temperature via the synergistic catalyzation of [TEPA][Im] and Pd/C. The effects of various factors on NO hydrogenation to NH3 were also investigated. Remarkably, Pd/C exhibited outstanding properties in the formation of NH3 with a high yield of 67% in the FIL [TEPA][Im] under the conditions of 100 °C and an H2 pressure of 0.5 MPa. [TEPA][Im] could be reused multiple times and the product NH3 could be recovered by flashing. [ABSTRACT FROM AUTHOR]

Understanding the cellular mechanisms by which amphiphilic ionic liquids (AmILs) induce cytotoxicity is an important step in the development of task-specific AmILs for safe industrial applications or as cytotoxic anticancer agents. Accumulated evidence suggests that AmILs kill cells by disrupting cellular membranes and/or inducing mitochondrial dysfunction. The cation of AmILs is lipophilic due to alkyl substitution, and lipophilic cations are a group of compounds known to accumulate in mitochondria in response to the membrane potential across the inner mitochondrial membrane (IMM). We therefore hypothesised that AmILs exert their cytotoxic effects by disrupting the IMM, the integrity of which is critical to several important cellular processes. Using fluorescence microscopy we show that a quinolinium-based AmIL rapidly accumulates in the mitochondria of HeLa cells. In a panel of AmILs we found that cytotoxicity correlates with their capacity to disrupt lipid bilayers, and that AmILs produce a range of cellular effects consistent with permeabilisation of the IMM at cytotoxic concentrations. Thus, AmILs depolarise the IMM, inhibit oxidative phosphorylation and ATP synthesis, and induce ROS formation. These effects were only induced by AmILs with aromatic cations substituted with long (decyl) alkyl chains, as these features promote accumulation in, and permeabilisation of, the IMM. These mechanistic insights help explain the structure–activity relationship governing AmILs cytotoxicity and may be used to rationally design either safe or cytotoxic AmILs. [ABSTRACT FROM AUTHOR]

Pure or highly concentrated ionic liquids (ILs, CIL > 40% v/v) have been widely applied for the preparation of value-added products from polysaccharides by breaking their hydrogen bonds. Reducing the dosage of ILs would benefit the establishment of a greener process. However, the effect of low-concentration ILs on the pretreatment of polysaccharides, especially water-soluble recalcitrant polysaccharides, has not been fully investigated. In this study, aqueous [Bmim]Cl (1-butyl-3-methylimidazolium chloride) with different dilution ratios was applied to treat xanthan gum (XG) and assist XG hydrolysis. Structural characterization and hydrolysate analyses showed that 1% (v/v) [Bmim]Cl could effectively break intramolecular hydrogen bonds of XG through the binding of [Bmim]+ to XG side chains, disrupting the XG conformation. Such changes increased the accessibility of XG for chemical reagents. Moreover, [Bmim]Cl could significantly increase the content of hydroxyl and superoxide radicals (from H2O2) in the reaction system. These interactions strengthened the acidic oxidative hydrolysis of XG. Notably, a low concentration of [Bmim]Cl was proved to inhibit the Maillard browning of the acidic oxidative hydrolysis system, which also contributed to XG degradation. Under hydrolysis conditions of 0.4 M HCl, 0.75% (w/v) H2O2 and 1% (v/v) [Bmim]Cl for 4 days at 80 °C, XG could be hydrolyzed into a mixture with a high dextrose equivalent value of 29.16% containing 25 types of oligosaccharides. Meanwhile, the XG hydrolysates showed good antioxidant ability and elicitor activity against soybean cotyledon. Our work should be valuable for establishing a green and economic platform for valorizing water-soluble recalcitrant polysaccharides. [ABSTRACT FROM AUTHOR]

In recent years, chemical recycling to monomer (CRM) has emerged as an advanced strategy to deal with post-consumer plastics. However, because it usually takes a long time to react at a relatively high temperature, CRM suffers from side reactions and energy consumption issues. In this work, a Brønsted–Lewis acid ionic liquid/polyhydroxy-compound system ([Et3NH][ZnCl3]/pentaerythritol) was developed as a bifunctional reagent for dissolving poly(p-dioxanone) (PPDO) and highly efficiently catalysing its CRM. In situ addition of the polyhydroxy-compound significantly prevented the formation of byproduct, i.e., cyclic PPDO, by converting it back to depolymerizable linear PPDO. Therefore, both the CRM efficiency and selectivity were obviously improved. At 160 °C, PPDO was almost fully depolymerized to the PDO monomer in only 8 minutes with 99.9% GC purity of yield. Moreover, [Et3NH][ZnCl3]/pentaerythritol could be reused at least 5 times without post-processing and its chemical structure and efficiency remained intact. According to the kinetic study, the activation energy of depolymerization was calculated to be 64.81 kJ mol−1, half lower than the traditional method. Based on NMR titration, the catalytic mechanism was discussed. Importantly, according to the assessment of the energy economy factor, environmental factor, and environmental energy impact factor, the strategy developed in this work is better than all of the related works in greenness. [ABSTRACT FROM AUTHOR]

According to the requirements of sustainable green development, the efficient green synthesis of fluorine chemical products is an inevitable trend. In this work, we used ionic liquids as an effective catalyst in an important fluorochemical reaction – hexafluoropropylene dimerization for the first time. The effects of ionic liquids with different spatial positions, substituents and nucleophilic anions on the catalytic performance of hexafluoropropylene dimerization were systematically studied. The results showed that the strong nucleophilic trisubstituted thiocyanate imidazole ionic liquid [C6mmim][SCN] had the highest activity under the optimum reaction conditions, the turnover frequency (TOF) was 108.36 h−1 and the selectivity was 97.96%. Compared with the traditional metal salt catalyst system, the catalytic activity of ionic liquids was double. In addition, based on the XPS analysis results and density functional theory (DFT), a possible reaction mechanism was proposed. The effective catalytic activity of ionic liquids was mainly attributed to the strong nucleophilicity of anions and the weak interaction between cations and anions. This work will successfully provide a green synthesis route for hexafluoropropylene dimerization and further promote the efficiency and greening of fluorine chemical reactions. [ABSTRACT FROM AUTHOR]

Shaping cellulose into functional materials entered a new era with the introduction of ionic liquids as novel, green solvents about 20 years ago. As non-volatile solvents with high thermal and chemical stability, ionic liquids can provide an environmentally more benign tunable platform for cellulose processing, compared to existing technologies. The past decades have seen fruitful efforts devoted to the development of materials based on ionic liquid/cellulose processing systems. In this review we discuss the experiences gained, and highlight the emerging applications. In particular, coatings and thin film applications for structural materials (e.g., for packaging), thin film filtration membranes, immobilisation of enzymes, and catalytically active nanoparticles, separator membranes and conductive composites for energy storage and other electronics applications, cellulose/biopolymer green biocomposites, cellulose-based ionogels, hydrogels and aerogels, and cellulose-based or composite fibres will be discussed in detail. We will also take a critical look at the perspectives of this field. The use of a certain grade of technical cellulose, and the purity of the prepared materials should be more carefully justified in the future, as they have an influence not only on the properties of the fabricated material, but also on the economics of the process. Furthermore, to make ionic liquids truly green solvents, and competitive alternatives to existing technologies, more studies are needed on recyclability after material fabrication, and on ways to minimise the energy consumption of such processes, among other issues. [ABSTRACT FROM AUTHOR]

As a fuel or energy carrier, hydrogen has been identified as a key way to decarbonize electricity, industry, transportation, and heating sectors. Hydrogen can be produced by a variety of methods, among which water electrolysis driven by renewable energy is sustainable and nearly carbon-free. To use hydrogen widely, storage and transportation over long distances are another key issue. Apart from storage at high pressure and low temperature, hydrogen can be stored in organic compounds via chemical bonding under relatively mild conditions. Efficient utilization of hydrogen includes hydrogen fuel cells as an alternative to internal combustion engines. From the above scenarios, catalysis and reaction media are the key factors for realizing hydrogen energy implementation. Ionic liquids (ILs) offer new opportunities due to their tunable functional groups, low vapor pressure, and stable structures as additives, solvents, and charge transfer materials. ILs are known to produce solid catalysts with controllable properties, decorate solid catalysts with modified electrons and geometric structures, and serve as electrolytes and hydrogen storage media. This review summarizes and recaps the recent progress in how ILs act as a cornerstone to support the production, storage, and utilization of hydrogen. Furthermore, critical challenges and future research directions of ILs in hydrogen energy applications are also outlined. [ABSTRACT FROM AUTHOR]

Dissolution of lignocellulose is of significant importance for its utilization and transformation. However, it remains a great challenge to efficiently and rapidly dissolve lignocellulose under mild conditions owing to the significant lack of efficient solvents for lignocellulose dissolution. Herein, robust solvent systems were designed by a combination of ionic liquids (ILs), ethanolamine (EA), and organic superbases for the dissolution of lignocellulose. It was observed that the prepared solvents (denoted as the IL/EA-superbase) could efficiently dissolve lignocellulose at mild temperatures (below 100 °C). In particular, the EmimOAc/EA-DBN system showed the best performance, and the solubility values of Populus tomentosa, sugarcane bagasse and Miscanthus giganteus at 90 °C could reach up to 3.8%, 9.5% and 20% (g per 100 g solvent), respectively. It was revealed that EA-superbase effectively participated in the interaction between ILs and lignocellulose, thus promoting the dissolution process. A systematic study revealed that the good performance of the developed solvents toward lignocellulose dissolution resulted from the synergistic effect of the three constructed components to make the solvent have a suitable capacity for the formation of hydrogen-bonding and an appropriate microstructure. [ABSTRACT FROM AUTHOR]

Herein we describe the syntheses of a series of molybdate and polyoxomolybdate ionic liquids (ILs), their full spectroscopic characterisation (FT-IR, 1H-, 13C-, 31P-, and 95Mo-NMR and ICP-MS), a comparison of their properties, and their applications as bifunctional catalysts for CO2 insertion into epoxides. The synthetic procedures to obtain ILs rely on anion exchange and acid–base reactions, including an innovative route for the synthesis of molybdate ionic liquids (Mo-ILs) using a halide-free organic IL precursor. The use of Mo-ILs as catalysts for CO2 fixation was investigated using 1,2-epoxyhexane as a model substrate. In the presence of 2.5 mol% of tetrabutylammonium molybdate, hexane carbonate was obtained in up to 86% yield at T = 120 °C, p0(CO2) = 30 bar in t = 9 h, under solventless conditions and without any added halide co-catalysts. The substrate scope was broadened to other 12 terminal and internal epoxides; moreover, the reaction was scaled up to 2 g of the substrate and catalyst recyclability was demonstrated up to 5 recycles. [ABSTRACT FROM AUTHOR]

Among the materials used in biomass processing techniques, ionic liquids (ILs) are found to be more efficient and environmentally friendly, especially in terms of lignin and cellulose dissolution. However, designing IL molecules and applying them to green chemical processes at low temperatures also remains a grand challenge. Here, we design and fabricate two IL molecules containing an extended benzene ring conjugated system. Surprisingly, the IL molecules can efficiently catalyze H2O2 to produce ˙OH radicals at room temperature and very low concentrations, and also improve the dissolution of lignin in cottonseed hulls and the swelling of cotton fiber. There are strong interactions between the IL molecules with an extended π-conjugated system and cellulose/lignin macromolecules verified via density functional theory (DFT) calculations. The activation energy of the hydrogen peroxide reaction is appreciably reduced by generating free radicals with the catalysis of the IL molecules. The IL/H2O2 system was used in cotton cold pad-batch bleaching. Cotton fabric can be scoured and bleached at room temperature via one step, saving a lot of energy and chemicals. The green chemical processes catalyzed by the IL molecules afford enormous advantages in energy saving and efficiency improvement. [ABSTRACT FROM AUTHOR]

Keratin is a biopolymer with high potential for biomaterial production, being principally investigated in hydrogel and film forms for use in tissue-engineering applications. Aiming to find sustainable solvents and develop an efficient keratin recovery process, this work used an aqueous solution of bio-based ionic liquid (IL) for the dissolution of chicken feathers. Complete dissolution of chicken feathers in an aqueous solution of cholinium acetate ([N111(2OH)][C1CO2]) was conducted at a solid : liquid weight ratio of 1 : 20 w/w, 100 °C for 4 h. An experimental design was carried out to optimize the keratin recovery conditions, investigating coagulant solvent, solution : coagulant weight ratio, and time. Under the optimal conditions (20.25 wt% of ethanol in water, 5 h, and solution : coagulant ratio of 1 : 1.45 w/w), 93 wt% of keratin was recovered. The IL was shown to be reusable in four successive cycles, with a yield of around 95 wt% and no significant losses in the efficiency of keratin recovery. These results demonstrate that an aqueous solution of [N111(2OH)][C1CO2] can lead to effective keratin recovery, serving as the basis for the development of a more effective and environmentally friendly process to recover biopolymers from waste. Due to the relevance of the developed process, techno-economic assessment through a comprehensive sensitivity analysis was carried out, evaluating a virtual operating biorefinery and showing a pathway that can enable the commercialization of produced keratin by the developed process. According to the process simulation, the minimum selling price for keratin is 22 $ per kg, with a small positive CO2 emission (4.04 kgCO2 kgkeratin−1), making this process suitable for biomedical and cosmetic applications. [ABSTRACT FROM AUTHOR]

The valorization of abundant agrowastes into chemicals and advanced materials is of key importance in the context of the circular bioeconomy and biorefinery. Herein, we report the ionothermal carbonization (ITC) of sugarcane bagasse, a fibrous residue made of lignocellulose, to engineer advanced carbonaceous materials, namely ionochars. We prepared a series of imidazolium tetrachloroferrate ionic liquids (IL) bearing modular substituents, e.g., alkyl chains with different lengths or benzyl groups. The effect of the cation on both textural and morphological properties is highlighted. Ionochars with high specific surface area (up to 800 m2 g−1), tuneable pore volume (up to 0.8 cm3 g−1), singular nanostructures and adjustable CO2 uptake/retention were obtained. [ABSTRACT FROM AUTHOR]

The simultaneous achievement of large surface areas and high IL contents in porous materials are highly beneficial for efficient carbon dioxide (CO2) capture and atmospheric fixation. Herein, a series of porous hypercrosslinked poly(ionic liquid)s (HPILs) are successfully developed through a two-step synthetic strategy, including free radical self-polymerization of a specific benzyl bromide-tethered imidazole ionic liquid (IL) to fabricate a linear PIL as a precursor, and a subsequent Friedel–Crafts alkylation between the precursor and the crosslinker for hypercrosslinking. The HPILs featured large surface areas of up to 855 m2 g−1 along with a hierarchically nanoporous structure, high IL contents (2.19–2.91 mmol g−1) and satisfactory CO2-philic properties. By virtue of the combined advantages, HPILs served as metal-free heterogeneous catalysts for solvent-additive-free CO2 cycloaddition with epichlorohydrin at 80 °C and 0.1 MPa CO2 for 24 h, presenting high catalytic activity and stable reusability. A high yield of 99.0% coupled with a turnover frequency (TOF) of 6.0 h−1 was achieved, much higher than most of the reported metal-free heterogeneous catalysts, even superior to homogeneous analogues. Furthermore, various epoxides, including large-sized epoxides, were effectively converted into carbonates with high yields, affording good substrate applicability. This work reports a facile and universal approach for the construction of porous HPILs with both great porosities and high IL contents towards efficient chemical fixation of CO2 under mild conditions. [ABSTRACT FROM AUTHOR]

In this work, we describe the preparation and characterization of supramolecular ionic liquid gels based on binary mixtures of biopolymers, comprising chitosan, chitin, cellulose and lignin. The gels were obtained in ionic liquids differing in the cation or the anion, with no need for a cross-linking agent or acid treatment. The materials obtained were characterized for the minimum gelation concentration, porosity, swelling and rheological properties, finding a prominent influence of the nature of the ionic liquid anion. Then, we investigated the ability of the gels to scavenge free radicals, finding that the gels exhibit a higher antioxidant ability than their individual components. Moreover, our gels showed a bactericidal activity toward Gram-positive and Gram-negative bacterial strains like Streptomyces coelicolor and Escherichia coli, respectively. The kinetics of bacterial cell viability showed that the gel based on a chitosan : chitin mixture in the IL [bmim][Cl] was the fastest acting against E. coli, with a practically total killing of bacterial cells within 30 min. Once again, a major influence of the ionic liquid anion was detected. Finally, we found an inverse relationship between the antioxidant and antimicrobial activities of our gels. [ABSTRACT FROM AUTHOR]

An efficient, simple, metal and ligand free, regioselective hydroboration of alkenes has been developed using pinacolborane (HBpin) as a reducing reagent and 1-ethyl-methylpyrrolidinium triflate [EMPyrr][OTf] as a non-corrosive and recyclable organocatalyst. The described protocol is scalable and compatible with a variety of alkenes offering the desired organoboron compounds in moderate-to-excellent yields. The system was reused in 30 cycles with comparable effectivity and stable selectivity of the process, increasing its sustainability. The utility of the obtained alkylboronates was checked in various subsequent transformations such as Suzuki–Miyaura coupling, Zweifel olefination and oxidation. Moreover, a reaction mechanism based on previously reported literature and NMR studies was proposed. [ABSTRACT FROM AUTHOR]

Upgrading biomass-derived platforms to functionalized aromatics by a tandem Diels–Alder (DA) cycloaddition–aromatization strategy has attracted broad attention. However, three challenges exist: improving the equilibrium of DA cycloaddition, controlling the regioselectivity of DA adducts, and increasing the stability of the cycloadduct. Herein, an intramolecular cycloaromatization strategy was developed for the direct upgradation of bio-furfurals to isoindolinones under liquid phase conditions via the selective formation of exo-DA adducts. The efficiency of the intramolecular DA cycloaddition was remarkably promoted by a defective Zn-BTC-SA catalyst quantitatively forming the desired regioselective exo-DA cycloadduct with higher thermal stability. Meanwhile, the co-existence of an acidic ionic liquid ([Hmim]HSO4) could facilitate the subsequent aromatization to generate isoindolinones in quantitative yields. Theoretical calculations elaborated the significance of the in situ formed exo-DA adducts with enhanced stability in the cascade conversion process. Moreover, this protocol is applicable to the production of a wide range of renewable isoindolinone derivatives and commercial medicines in excellent yields (>92%) and is suitable for gram-scale reactions. [ABSTRACT FROM AUTHOR]

The synthesis of ionic liquids can generate large amounts of waste and use toxic or expensive raw materials. In this short review, we focused on one of the most promising pathways to large scale environment-friendly productions of ionic liquids. The "dialkylcarbonate route" has already allowed the preparation of more than one hundred original ion pairs, avoiding the use of pollutant alkylating agents and non-sustainable anion exchange materials, in a halide-free and water-free process. [ABSTRACT FROM AUTHOR]

The preparation of regenerated cellulose (RC) materials with high performance via dissolution processing is dependent on the properties of the cellulose solution and the conditions of the coagulation bath. Herein, a novel sustainable superbase-derived ionic liquid (SIL, [DBUH][CH3CH2OCH2COO]) with excellent solubility (14.83 wt% at 80 °C) for dissolving wood pulp (DWP; DP = 526) is demonstrated. The rheological characteristics of DWP/[DBUH][CH3CH2OCH2COO] solutions and the regeneration process of cellulose were first systematically investigated. The results indicated that the DWP concentration significantly affected the apparent viscosity (η), structural viscosity index (Δη), overlap concentration (c*), entanglement concentration (ce), storage modulus (G′), and loss modulus (G′′). Notably, a 12 wt% DWP solution possessed favourable temperature-sensitive properties with an activation energy (Eη) of 55.428 kJ mol−1 and a gel–sol transition temperature of 59.5 °C, presenting superior viscoelasticity to that of imidazolium-based ILs/cellulose in fibre spinning. Moreover, these properties of DWP solutions offered essential advantages for the subsequent preparation of RC films. Comparing the properties of RC films prepared in various coagulation baths, cellulose films regenerated from ethanol exhibited high transparency (up to 90% at 800 nm) and outstanding mechanical properties (tensile strength: 120 MPa; elongation at break: 12%). In this regard, it was inferred that the diffusion rates between [DBUH][CH3CH2OCH2COO] and ethanol contributed to the construction of RC films with high crystallinity and a dense morphology. Hence, [DBUH][CH3CH2OCH2COO] as a solvent and ethanol as a coagulation bath can be a promising processing platform for manufacturing high-performance cellulose materials. [ABSTRACT FROM AUTHOR]

The poultry-processing industry generates large quantities of waste rich in keratin, a fibrous protein representing around 90 wt% of chicken feathers, which is currently disposed of by landfilling or incineration. Keratin is commonly recognized as a renewable biopolymer resource used in the preparation of biomaterials (e.g., films and hydrogels) of interest in biomedical applications. Even though research on keratin recovery from chicken feathers started many years ago, very few keratin materials from this source have been developed due to keratin's low solubility in most common solvents and poor protein recovery yield. Although ionic liquids (ILs) have been reported as alternative solvents with high dissolution capability for several biopolymers, keratin recovery from chicken feathers using aqueous solutions of ILs has not been investigated to date. Considering the Green Chemistry Principles (especially the first one: zero waste) and circular economy concepts, in this work, we show that chicken feathers can be effectively dissolved in an aqueous solution of 1-butyl-3-methylimidazolium acetate (80 wt%), greatly enabling keratin recovery and preparation of keratin biofilms. Keratin recovery from the IL aqueous solution was optimized considering the coagulant type, solution : coagulant weight ratio, temperature, and time, with the coagulant type being the variable with higher influence on the recovery process. Under the best conditions (ethanol, 1 : 2 w/w, 5 °C, and 1 h), 90 wt% of keratin was recovered. IL recovery and reuse were also evaluated, and 82 wt% of recovery yield was achieved at the end of the third cycle. The recovered keratin was characterized, confirming the required physicochemical properties. A keratin film was finally prepared and characterized through cell viability, oxidative stress and wound healing assays, opening the path for the use of keratin films in biomedical applications. [ABSTRACT FROM AUTHOR]

The present study investigated the ready biodegradability of naturally occurring and nature-inspired pyridinium cations for the design of greener or sustainable ionic liquids (ILs). Our results showed that trigonelline ([C1COOHPy][Cl]) and 1-methylnicotinamide ([C1CONH2Py][I]) were completely mineralizable and non-toxic under the conditions of the Closed Bottle Test (CBT), while [C1CONH2Py][I] was readily biodegradable. In contrast, the nicotinium structures, 1-methylnicotinium and 1,1′-dimethylnicotinium, were biologically persistent but non-toxic to the inoculum, whereas S-nicotine itself was identified as readily biodegradable. The biodegradability of these pyridinium structures was compared with that of the commercial pyridinium ILs [C1Py][PF6] and [C2Py][Br] having short alkyl residues. While [C2Py][Br] demonstrated only partial but not ultimate biodegradation, [C1Py][PF6] was shown to be readily biodegradable in the CBT. HRMS confirmed the biodegradation results. The results also showed the negative influence of short alkyl residues on biodegradability. Based on the results, new highly biodegradable and non-toxic pyridinium ILs can be designed to limit the accumulation of persistent ILs in the aquatic environment. Moreover, since some of our pyridinium structures and all their pyridine precursors can be isolated either from renewable sources or waste materials, ILs based on [C1COOHPy][Cl], [C1CONH2Py][I] and [C1Py][PF6] as cationic scaffolds can also be referred to as sustainable ILs if the anion fulfills the criteria too. Besides their physicochemical and environmental properties, the use of such methylated pyridinium blocks offers the opportunity for biotechnological synthesis using S-adenosyl methionine as the methyl donor catalyzed by N-methyltransferases and therefore the avoidance of commonly used carcinogenic methylating agents such as iodomethane or dimethyl sulfate. Thus, the synthesis of these ILs can be improved towards sustainability and the principles of Green Chemistry (e.g., 3rd less hazardous chemical synthesis, 9th catalysis, and 12th inherently safer chemistry for accident prevention) and an inherently safer pathway to ILs can be created. [ABSTRACT FROM AUTHOR]

The establishment of the place of Deep Eutectic Solvents (DESs) as a new class of green solvents was essentially grounded on naïve comparisons with Ionic Liquids (ILs), since both are composed of charged compounds. The easiness of DESs' preparation afforded the quick preparation and utilization of a massive number of solvents and their use in wide variety of applications with minimal fundamental knowledge of their thermophysical properties and phase equilibria studies. As time went on, the need to define DESs from the thermodynamic point of view and to differentiate them from other classes of solvents was imperative. This perspective review aims at dispelling some myths about DESs through the use of experimental data and computational chemical calculations and establishing fair comparisons with other classes of solvents, ILs, eutectic solvents (ESs) and volatile organic compounds (VOCs), so that clear and sound conclusions can be drawn. Several important parameters typically used to characterize solvents and that have been much used to justify DESs' wide range of applications, such as vapor pressure, thermal stability, polarity, toxicity and water miscibility, were accessed for these different solvents and comparisons were established. Moreover, a comparative analysis in a selected research area, biopolymer dissolution and treatment, was chosen to illustrate the unique potential of ILs and DESs and the challenges that still need to be addressed. Literature available for the diverse polysaccharides selected (cellulose, hemicellulose and chitin) and lignin highlighted pros and cons and the different level of knowledge gained to date for both ILs and DESs. This part is complemented by recycling and techno-economic considerations for the two classes of solvents, which are additional key aspects to consider for the development of an effective integrated biorefinery process. The conclusion is obvious: DESs are a new class of solvents, with distinct properties from other classes of solvents which are essentially dependent on the properties of their constituent compounds. Therefore, when starting compounds are wisely selected, DESs become an additional and promising pathway in the pursuit of environmentally friendly solvents to replace traditional VOCs for a given application. However, some fundamental studies are still needed to fully understand these systems and define their most effective areas of application. [ABSTRACT FROM AUTHOR]

Covalent organic nanosheets (CONs) are receiving tremendous interest for their potential in versatile applications. However, the synthesis of CONs usually suffers from the use of toxic solvents, low yields and uncontrollable thickness. Here, we report a green, high yield, and scalable strategy to strip two-dimensional imine-linked covalent organic framework (COF) powders in water using bi-functional ionic liquids as both the intercalator and stabilizer under ambient conditions. It is shown that the exfoliation yield reaches up to 66.6%, which is a record value for the delamination of CONs from bulk COF powder. The thickness of CONs is mainly in the range from 0.4 to 2.0 nm and the lateral size is large up to a few hundred nanometers. Importantly, the aqueous IL solutions can be reused and recycled for the exfoliation of CONs. The acid–base and hydrogen bond interactions between CONs and cations of the ILs are found to play critical roles in the delamination and stability of CONs. Furthermore, the CONs without any additives such as metals, photosensitizers, and sacrificial agents have been used as catalysts for photocatalytic CO2 reduction with gaseous water to yield CO in the gas phase under visible-light irradiation. The production rate of CO is 132.2 μmol g−1 h−1, which is twice that by the bulk COF powder, and outperforms most visible-light driven metal-free COFs reported so far. Therefore, the liquid phase stripping approach reported here possesses tremendous potentiality in mass production of CONs for high efficiency photocatalysis of CO2 reduction in the gas phase. [ABSTRACT FROM AUTHOR]