Acetate Ionic Liquid Research Articles

DABCO‐Saccharin Acetate as a Novel, Recyclable and Metal‐Free Catalyst for Eco‐Friendly Synthesis of Various Pyridazino[1,2‐a]indazole and 1H‐indazolo[1,2‐b]phthalazine Heterocycles Under Solvent‐Free Conditions

AbstractIn this research various pyridazino[1,2‐a]indazole and 1H‐indazolo[1,2‐b]phthalazine and 1H‐indazolo[1,2‐b]phthalazine derivatives were produced with a high yield via a multi‐component reaction of dimedone, aldehyde, hydrazine and anhydride compounds in the presence of a novel DABCO‐Saccharin acetate ([DABCOH][Sac‐CH3CO2]) ionic liquid under microwave irradiation. The applied method for producing these heterocyclic compounds demonstrated a number of desirable traits, including quick reactions, high yields of the final product, and straightforward separation of the product and catalyst from the reaction mixture.

Choline Oxidase and Choline Ionic Liquids in Biocatalytic Heme Peroxidase Cascades

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

Palladium supported on alumina as a highly active heterogeneous catalyst for direct arylation of 6-substituted imidazo[2,1-b]thiadiazole via C[sbnd]H bond activation reaction

Fast, atom-economical, phosphine-free, and eco-friendly microwave-irradiated reactions permitting the “green synthesis” of 5,6-disubstituted imidazo[2,1-b]thiadiazole derivatives using heterogeneous palladium catalyst in triethylammonium 2-(1,1-dioxido-3-oxobenzo[d]isothiazol-2(3H)-yl)acetate ([Et3NH][Sac-CH3CO2]) ionic liquid via CH bond activation reaction of 6-substituted imidazo[2,1-b]thiadiazole derivatives, are reported. This method provides a straightforward route to a wide variety of substituted imidazo[2,1-b]thiadiazoles and has the advantages of reusability of the heterogeneous catalyst, simple methodology, high yields, and easy work-up.

Novel application for graphene oxide-based ionanofluids in flat plate solar thermal collectors

This study presents new ionanofluids (INF) composed of 1-ethyl-3-methylimidazolium acetate ionic liquid (IL) and graphene oxide (GO) nanoparticles which have been assessed for the first time in an experimental flat plate solar thermal collector (FPSC). For this purpose, four types of INFs were synthesized, maintaining a constant concentration of GO nanoparticles dispersed in different base fluids: ionic liquid (IL/GO), a mixture of ionic liquid and water in varying concentrations (IL-water (75–25)%/GO and IL-water (50–50)%/GO), and water (Water/GO). These four INFs were characterized and their thermophysical and physicochemical properties were determined. The results indicated a 37.4% improvement in efficiency and up to a 2.5-fold increase in temperature within the collector when the IL was applied exclusively as the base fluid, compared to water. Furthermore, IL/GO demonstrated excellent stability, showing no signs of deterioration or nanoparticle precipitation two years after preparation and testing. These findings suggest that INFs based on IL and GO nanoparticles significantly enhance the efficiency of FPSC, presenting a promising option for solar energy applications and opening a new research avenue for INFs in the production of domestic hot water.

Multifunctional anion-cation modulation engineering for Sn-Pb perovskite solar cells

The binary tin and lead (Sn-Pb) perovskites are a significant cornerstone for all-perovskite tandem devices due to their high efficiency, low toxicity, and narrow bandgap properties. However, the fast crystallization of the perovskite film and the facile conversion of Sn2+ to Sn4+ during the preparation process are major obstacles to achieving remarkable Sn-Pb perovskite solar cells (PSCs). Herein, we develop a multifunctional anion-cation modulation strategy to synthesize high-quality FAPb0.5Sn0.5I3 (Eg∼1.24 eV) perovskite films by mixing methylamine acetate (MAAc) ionic liquid with the PbI2 and SnI2 solutions through a two-step sequential deposition process. MA cations tend to insert the tin/lead-halogen octahedral framework and occupy the A-site in the first-step. Subsequently, the volatile MA cations can produce ion exchange reactions with FA+ from the formamidinium iodide in the second step, leading to high quality crystallization process. Additionally, the Ac anions can efficiently suppress Sn2+ oxidation with balancing the crystallization rate of the Pb/Sn components, and passivate the defect sites located on the grain boundary and surface, owing to the strong coordination of Ac- with Sn2+ and Pb2+. As a result, the optimized PSC reaches a power-conversion efficiency of 21.22 %, which is the highest value reported for FAPb0.5Sn0.5I3 based solar cells with a two-step method, compared to the control device with 12.86 %. Moreover, the perovskite devices show prominent reproducibility and stability performance, maintaining >80 % of the initial efficiency after being stored in the N2-filled glovebox for 1000 h.

Two-Step Perovskite Solar Cells with > 25% Efficiency: Unveiling the Hidden Bottom Surface of Perovskite Layer.

While significant efforts in surface engineering have been devoted to the conversion process of lead iodide (PbI2) into perovskite and top surface engineering of perovskite layer with remarkable progress, the exploration of residual PbI2 clusters and the hidden bottom surface on perovskite layer have been limited. In this work, a new strategy involving 1-butyl-3-methylimidazolium acetate (BMIMAc) ionic liquid (IL) additives is developed and it is found that both the cations and the anions in ILs can interact with the perovskite components, thereby regulating the crystallization process and diminishing the residue PbI2 clusters as well as filling vacancies. The introduction of BMIMAc ILs induces the formation of a uniform porous PbI2 film, facilitating better penetration of the second-step organic salt and fostering a more extensive interaction between PbI2 and the organic salt. Surprisingly, the oversized residual PbI2 clusters at the bottom surface of the perovskite layer completely diminish. In addition, advanced depth analysis techniques including depth-resolved grazing-incidence wide-angle X-ray scattering (GIWAXS) and bottom thinning technology are employed for a comprehensive understanding of the reduction in residual PbI2. Leveraging effective PbI2 management and regulation of the perovskite crystallization process, the champion devices achieve a power conversion efficiency (PCE) of 25.06% with long-term stability.

Facile Separation of Acetic Acid from 1-Ethyl-3-methylimidazolium Acetate Ionic Liquid with the Aid of a Protic Solvent.

1-Ethyl-3-methylimidazolium acetate (EmimAc), an excellent solvent for cellulosic biomass, is expected to be utilized in chemical conversion, such as in biomass acetylation with acetic anhydride. The corresponding carboxylic acid, acetic acid (AcH), is quantitatively generated as a byproduct and should be separated from EmimAc for recycling. However, the strong interaction between EmimAc and AcH makes their separation difficult under moderate conditions. This study examined the efficacy of protic solvents in distillation and extraction to weaken this interaction through solvation or hydrogen-bonding interactions. The separation efficiency of AcH from EmimAc via distillation increased as the boiling point of the protic solvent increased. Water addition was more effective than the addition of alcohols with boiling points similar to those of water such as 1-propanol and 2-butanol. Furthermore, the favorable effect of water addition on the extraction of AcH was confirmed using common organic solvents, such as diisopropyl ether, diethyl ether, and ethyl acetate. The partition coefficient (α) of AcH between the aqueous and organic phases increased with an increasing dielectric constant of the organic solvent, whereas the α value of EmimAc decreased. Repeated treatments in both distillation and extraction facilitated the complete separation of AcH from EmimAc.

Solubility of seven amino acids in two acetate ionic liquids from 298.15 K to 328.15 K

The number of studies on the solubilities of amino acids in pure ionic liquids is currently very scarce. Focusing on fundamental studies for the recovery of added-value compounds from fisheries and aquaculture discards, in this work the solubility of several amino acids in acetate ionic liquids and their mixtures with water were determined at temperatures ranging from 298.15 K to 328.15 K and atmospheric pressure. Sharing the acetate anion, solubilities were higher in the ionic liquid with 1-ethyl-3-methylimidazolium than with 1-hexyl-3-methylimidazolium cation. Increasing temperatures resulted in enhanced solubilisation. Solubilities in the ionic liquids ranked thus: Pro > OH-Pro > Lys·HCl > Ala > Gly > Cys, with an intermediate position of Arg (the amino acid most influenced by the hydrophobic environment and temperature). In the case of the mixtures with water, the ranking was Pro > Lys·HCl > Ala > Arg > OH-Pro > Gly > Cys. The van't Hoff equation adequately correlated experimental solubilities in the range of temperatures studied, and the process of dissolution was found endothermic and entropy-driven in all the cases. The ionic liquid 1-ethyl-3-methylimidazolium should be considered for the target application and the water content a design variable to analyse.

Characterization and electrochemical properties of TiO2-rNTs/SnO2–Sb/PbO2 electrodes for the mineralization of persistent organic pollutants using anodic oxidation coupled Electro-Fenton treatment: Effect of precursor selection

The present study compares the effect of using different solvents on the electrochemical properties of the reduced TiO2 nanotubes (TiO2-rNTs) layered Ti/TiO2-rNTs/SnO2–Sb/PbO2 anodes. The electrodes are prepared using three different solvent-based precursors: (i) isopropanol, (ii) ethylene glycol and citric acid (Pechini method), and (iii) 2-hydroxyethylammonium acetate (2HEAA) ionic liquid (IL) via the thermal decomposition route. The decomposition mechanism of precursor solutions was explored using the thermogravimetric (TGA) analysis. Further, the physicochemical properties of the electrodes are examined using Field emission Scanning Electron microscopy (FE-SEM), X-ray diffraction spectroscopy (XRD), and X-ray photoelectron emission spectroscopy (XPS). The results revealed that solvents with higher viscosity and slower decomposition rates support better film uniformity and higher stability of the electrode. The TiO2 -rNTs bottom layer and PbO2 top layer helped obtain higher film stability, increased working potential window (2.2 V vs. SHE) of the electrode, and the repeatability of the results. The performance of different electrodes based on the precursor solution is found as IL ≫ Pechini > Isopropanol. 4-chlorophenol (4-CP) is used as a model pollutant to test the performance of IL-Ti/TiO2-rNTs/SnO2–Sb/PbO2 anode in an anodic oxidation (AO) coupled electro-Fenton (EF) treatment. Further, the reliability of the electrode is evaluated by mineralizing other persistent organic pollutants (POPs) like tetracyclin, phenol, 2-chlorophenol (2-CP), and 2,4-dichlorophenol (2,4-DCP). Under the optimized conditions, the proposed system was able to mineralize the tetracyclin, phenol, 2-CP, 2,4-DCP, and 4-CP up to 78.91, 82.07, 74.96, 78.78, and 69.3 %, respectively. Moreover, the degradation mechanism of chlorophenols is proposed.

Insight into the effect of pressure on the CO2 capture capacity and kinetics by a biochar-ionic liquid composite

Agave bagasse fibers-derived biochar (BCw) impregnated with 1-butyl-3-methylimidazolium acetate ionic liquid (IL) exhibited a considerably CO2 capture capacity at atmospheric (1.47 mmol/g at 25 °C and 1 bar) and moderately high pressure (1.32 mmol/g at 25 °C and 8.5 bar) under dynamic and static systems, respectively. Biochar-IL composites improved the CO2 capture capacity, kinetics, and selectivity (CO2/N2) by 4–90% compared with than of the bulk adsorbents. By increasing the working manometric pressure from 1 to 8.5 bar in a static high-pressure system, the CO2 capture capacity and kinetics of impregnated-biochar improved 2 times. Additionally, the biochar-IL composites were regenerated under a pressure swing adsorption (PSA) arrangement, where more than 70% of the desorption was attributed to the depressurization of the system. The proposed CO2 sorption mechanism suggests gas-solid physisorption and gas-liquid chemisorption at low pressure. At moderately high pressure (≥ 1 bar), the textural properties of the adsorbent play an important role. Moreover, this study provided evidence that the CO2 capture is not only related to the textural properties of the biochar, but also to its surface chemistry. The biochar-IL composite materials reported herein could be an option for CO2 capture at low and moderate pressures, which could reduce operating costs if implemented at large scale for CO2 separation from flue gases under a PSA design.

Experimental and molecular insights on the separation of indole from wash oil by tetraethylammonium‐based ionic liquids

AbstractA method for separating indole (IND) from wash oil by tetraethylammonium‐based ionic liquid (IL) was proposed. The distribution coefficient and selectivity of 304 kinds of ILs to IND were predicted by using Conductor‐like Screening Model for the Segment Activity Coefficient model, and quaternary ammonium acetate ILs have excellent separation performance. The experimental conditions were validated, and the influence of these conditions was explored. The IL could be recycled with water, and its structure and performance remained unchanged after repeated use four times. The extraction efficiency for real wash oil provided by a company reached 91.6%. The structure–performance relationship was explored by using quantum chemistry and molecular dynamic simulation. A process combining liquid–liquid extraction and azeotropic distillation was established for the separation of IND mixtures, and an IND product with a purity of 99.9% was obtained. This work comprehensively analyzed the separation of IND from wash oil using ILs at an atomic‐molecular‐experimental‐process scale.

Simulation of ionic-liquid extractive purification process of thiophene and m-xylene from their mixture with n-hexane by the molecular dynamics method

This paper deals with the results of simulation of extractive purification process of model diesel fuel (the mixture of n-hexane with thiophene and m-xylene) by molecular dynamics simulation using N-methylpyrrolidinium acetate ionic liquid as an extractant. The extractive purification process was simulated for several model fuel systems with different concentrations of sulfur and aromatic containing components. The ionic liquid exhibits high extractive ability, the degrees of desulfurization and dearomatization reach 85–90 and 60[Formula: see text]wt.%, respectively. The results were proved by experimental studies of a mixture by the ionic liquid. After 1[Formula: see text]h of contact of the ionic liquid and the model mixture, the degree of purification against thiophene was 94.2[Formula: see text]wt.%.

Enhancing CO2/(light gases) separation performance of Pebax-based mixed-matrix membranes by [BMIM][AC] ionic liquid

Incorporating the proper additive with an affinity towards target gases is considered a helpful strategy for simultaneously improving membrane permeability and selectivity. In this research, the superior features of polyetherblockamide polymer (Pebax1657), 1–Butyl3–methylimidazolium acetate ([BMIM][AC]) ionic liquid (IL), and aluminum oxide (Al2O3) nanoparticles were blended to produce efficient ternary mixed-matrix membranes for CO2 removal from light gases. The fabricated membranes structures have been evaluated by FTIR3ATR, FESEM, XRD, and DSC analyses. The permeation rates of unmixed CH4, N2, and CO2 gases through the resulting membranes were obtained at 25 °C and a feed pressure range of 4–10 bar. The gas permeability results showed that embedding Al2O3 nanoparticles as the loading up to 6 wt% increased the CO2/(light gases) separation performance. Besides, adding the IL into the polymer matrix boosted the membranes gas separation efficiencies caused by the increased CO2 solubility and their fractional free volume. The results also revealed that the resulting membrane containing 15 wt% of [BMIM][AC] IL and 6 wt% of Al2O3 nanoparticles, which has the best gas separation efficiency, is the optimum ternary mixed-matrix membrane. The comparison between the optimized membrane and the unloaded one efficiencies demonstrated that CO2/N2 and CO2/CH4 selectivities, along with the CO2 permeability, rose from 63.40, 19.93, and 115.39 Barrer for the unloaded membrane to 81.18, 25.14, and 166.42 Barrer for the optimum membrane (around 28 %, 26 %, and 44 % increments), at 10 bar and 25 °C, respectively.

Enhanced performance of MAPbI2.85Br0.15 perovskite solar cells via ionic liquid-induced surface passivation of perovskite films

Metal halide perovskite solar cells are considered as a competitive new force for next-generation photovoltaic, whereas the interfacial defect of perovskite films severely degrades the performance and stability of the devices. Herein, we introduce the 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac) ionic liquid to passivate lead-related defect on the surface of the MAPbI2.85Br0.15 perovskite films. The carbonyl groups of [EMIM]Ac coordinate with the uncoordinated lead ions on the perovskite surface, and meanwhile the [EMIM]Ac ionic liquid suppresses the formation of metallic lead, which effectively reduces the nonradiative recombination and improves the working stability. As a result, the power conversion efficiency of the solar cell with [EMIM]Ac treatment is improved from 16.95 % to 19.29 %. The unencapsulated device shows good stability and retains the initial efficiency of 95 % after being exposed in ambient environment for 240 h. Therefore, this ionic liquid surface passivation proposed in this work may shed light on the development and practical application of perovskite solar cells.

Efficient and Stable β-CsPbI3 Solar Cells through Solvent Engineering with Methylamine Acetate Ionic Liquid.

CsPbI3, an all-inorganic perovskite material with suitable band gap and excellent thermal stability, has garnered significant attention for its potential in perovskite solar cells (PSCs). However, CsPbI3 is susceptible to phase changes from photoactive to photoinactive in humid environments. Hence, it is crucial to achieve controllable growth of CsPbI3 perovskite thin films with the desired β-crystal phase and compact morphology for efficient and stable PSCs. Herein, MAAc was used as a solvent for the CsPbI3 precursor to fabricate β-CsPbI3 perovskite. An intermediate compound of CsxMA1-xPbIxAc3-x was initially formed in the MAAc solution, and during annealing, the MA+ and Ac- ions were replaced by Cs+ and I- ions, respectively. Furthermore, the incorporation of strong C═O···Pb coordination stabilized the black-phase β-CsPbI3 and facilitated the growth of crystals with a narrow vertical orientation and large grain size. As a result, the PSCs with an efficiency of 18.9% and improved stability (less than 10% decay after 2000 h of storage in N2 and less than 30% decay after 500 h of storage in humid air without any encapsulation) were achieved.

TiO2 nanostructures synthesized by electrochemical anodization in green protic ionic liquids for photoelectrochemical applications

This work studies the influence of the 2-hydroxyethylammonium acetate (2-HEAA) ionic liquid (IL) as an electrolyte in the electrochemical anodization of titanium for the synthesis of nanostructures for photoelectrochemical water splitting. Different 2-HEAA IL concentrations were used ranging from 0 to 4% v/v (IL-0 to IL-4) in electrolytes containing NH4F, water and ethylene glycol. Morphological, structural and electrochemical characterization of the nanostructures was carried out by means of field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and Mott-Schottky (MS) analysis. Additionally, photoelectrochemical tests were carried out in order to evaluate the efficiency of these materials as catalysts for water splitting applications. According to the obtained results, the electrolyte used for electrochemical anodization should contain little amount of NH4F (0.05 M) in order to obtain efficient nanostructures for photoelectrochemical purposes. However, small concentrations of IL (IL-0.25) resulted in nanostructures with higher photocurrents than doubling the NH4F concentration to 0.1 M. Therefore, the IL addition contributes to a more sustainable electrolyte formulation. The best photoelectrochemical response for water splitting processes was obtained for the nanostructures anodized with 1% v/v of 2-HEAA IL (IL-1) due to their high surface/area (higher pore diameters, smaller nanotubes wall thickness and higher nanotubes lengths), better crystallinity and electrochemical response, showing photocurrents more than 100% higher than the ones obtained for the nanotubes anodized without IL.

Effects of Different Isomers of Thiophenedicarboxylic Acids on the Synthesis and Properties of Thiophene-Based Sustainable Polyesters

The need for high-performance bioplastics brings new challenges to the design and preparation of next-generation sustainable bioplastics. With the emergence of a number of biobased monomers with a similar chemical structure in recent years, it is necessary to conduct a systematic and in-depth study on the effects of different isomers of monomers on the final material properties. Considering the potential barrier and bacteriostatic properties of emerging thiophene-based polyesters, this work systematically investigated the effects of different isomers of thiophenedicarboxylic acids (TFDCAs), 2,5-TFDCA and 3,4-TFDCA, on the synthesis and properties of polyesters by a combination of experiments and molecular simulations. A novel biobased polyester based on the 3,4-TFDCA isomer was synthesized and compared with its analogue. Theoretical studies modeled through population balances were performed to simulate the polymerization kinetics of these two polyesters. Contrary to expectations, we successfully prepared high-molecular-weight poly(1,4-butylene 3,4-thiophenedicarboxylate) (3,4-P14BTF) via melt polycondensation. As we know, for the polyesters based on the analogous phthalic acid, high molecular weights cannot be obtained by this strategy. Barrier properties were further systematically studied from both theoretical calculation and experimental perspectives. The superior gas and water vapor barrier properties of semicrystalline poly(1,4-butylene 2,5-thiophenedicarboxylate) (2,5-P14BTF) could be attributed to the decreased chain mobility and smaller fractional free volume. More intriguingly, they exhibited improved bacteriostatic effect compared to poly(lactic acid) (PLA), while no notable difference was observed between 2,5- and 3,4-isomers. 3,4-P14BTF could be degraded under milder conditions than 2,5-P14BTF enabled by methanolysis with the imidazole acetate ionic liquid catalyst. Therefore, in-depth analysis of the effects of different isomers of monomers should be considered for the design and preparation of new high-barrier and antibacterial polymeric materials for advanced applications such as biobased active food packaging and electronic encapsulation.

Study of the Plasticization Effect of 1-Ethyl-3-methylimidazolium Acetate in TPS/PVA Biodegradable Blends Produced by Melt-Mixing.

The first step towards the production and marketing of bioplastics based on renewable and sustainable materials is to know their behavior at a semi-industrial scale. For this reason, in this work, the properties of thermoplastic starch (TPS)/polyvinyl alcohol (PVA) films plasticized by a green solvent, as the 1-ethyl-3-methylimidazolium acetate ([Emim+][Ac-]) ionic liquid, produced by melt-mixing were studied. These blends were prepared with a different content of [Emim+][Ac-] (27.5-42.5 %wt.) as a unique plasticizer. According to the results, this ionic liquid is an excellent plasticizer due to the transformation of the crystalline structure of the starch to an amorphous state, the increase in flexibility, and the drop in Tg, as the [Emim+][Ac-] amount increases. These findings show that the properties of these biomaterials could be modified in the function of [Emim+][Ac-] content in the formulations of TPS, depending on their final use, thus becoming a functional alternative to conventional polymers.

Facile preparation of flame-retardant cellulose composite with biodegradable and water resistant properties for electronic device applications

The aim of the present study is to produce flexible, flame-retardant, water-resistant and biodegradable composite materials. The ultimate goal of this research is to develop simple processes for the production of bio-based materials capable of replacing non-degradable substrates in printed circuit board. Cellulose was chosen as a renewable resource, and dissolved in 1-ethyl-3-methylimidazolium acetate ionic liquid to prepare a cellulosic continuous film. Since flame retardancy is an important criterion for electronic device applications and cellulose is naturally flammable, we incorporated ammonium polyphosphate (APP) as a flame-retardant filler to increase the flame retardancy of the produced materials. The developed material achieved a UL-94 HB rating in the flammability test, while the cellulose sample without APP failed the test. Two hydrophobic agents, ethyl 2-cyanoacrylate and trichloro(octadecyl)silane were applied by a simple dip-coating technique to impart hydrophobicity to the cellulose-APP composites. Dynamic mechanical analysis indicated that the mechanical properties of the cellulosic materials were not significantly affected by the addition of APP or the hydrophobic agents. Moreover, the biodegradability of the cellulosic materials containing APP increased owing to the presence of the cellulase enzyme. The hydrophobic coating slightly decreased the biodegradability of cellulose-APP, but it was still higher than that of pure cellulose film.

Readily regenerable amine-free CO2 sorbent based on a solid-supported carboxylate ionic liquid

Accumulation of anthropogenic CO2 is undoubtedly the major cause of global warming. In addition to reducing emissions, minimising the threatening effects of climate change in the near future might also require the capture of enormous amounts of CO2 from point sources or from the atmosphere. In this regard, the development of novel affordable and energetically attainable capture technologies is greatly needed. In this work, we report rapid and greatly facilitated CO2 desorption for amine-free carboxylate ionic liquid hydrates as compared to a benchmark amine-based sorbent. Complete regeneration was achieved at moderate temperature (60 °C) over short capture-release cycles using model flue gas on a silica-supported tetrabutylphosphonium acetate ionic liquid hydrate (IL/SiO2), whereas the polyethyleneimine counterpart (PEI/SiO2) only recovered half its capacity after the first cycle in a rather sluggish release process under the same conditions. The IL/SiO2 sorbent achieved a slightly superior working CO2 capacity than PEI/SiO2. The easier regeneration of carboxylate ionic liquid hydrates, which behave as chemical CO2 sorbents leading to bicarbonate in a 1:1 stoichiometry, is due to their relatively low sorption enthalpies (≈40 kJ mol−1). The faster and more efficient desorption from IL/SiO2 fits a first-order kinetic model (k = 0.73 min−1), whereas a more complex process was observed for PEI/SiO2 (pseudo-first order initially, k = 0.11 min−1, pseudo-zero order at later stages). The remarkably low regeneration temperature, the absence of amines and the non-volatility of the IL sorbent are favourable assets to minimise gaseous stream contamination. Importantly, regeneration heats —a crucial parameter for practical application— are advantageous for IL/SiO2 (4.3 kJ g (CO2)−1) vs. PEI/SiO2, and fall within the range of typical amine sorbents indicating a remarkable performance at this proof-of-concept stage. Further structural design will enhance the viability of amine-free ionic liquid hydrates for carbon capture technologies.