Imidazolium Ionic Liquids Research Articles

Study on phase behavior of [C16mim] [br]/CAHS/n-butanol/n-hexane/water microemulsions: synergistic effect of ionic liquid-zwitterionic surfactants

The synergistic effect of ionic liquids (ILs) and anionic surfactants, ILs and cationic surfactants, and ILs and nonionic surfactants to form microemulsions has been studied by other researchers, while the synergistic effect of ionic liquids and zwitterionic surfactants to form microemulsions has not been reported. Here, we report the synergistic effect of imidazolium ionic liquid, 1-hexadecyl-3-methylimidazolium bromide [C16mim] [Br], and betaine-type zwitterionic surfactant, cocamidopropyl hydroxysultaine (CAHS), as surfactants, to form microemulsions with n-butanol, n-hexane and water. Phase behavior of the systems with different mass ratios of two surfactants, varied mass ratios of surfactant to cosurfactant (Km), and different temperatures are investigated by pseudo-ternary phase diagrams. The single-phase region of the microemulsion is maximized when the ratio of CAHS to [C16mim] [Br] is 1:4 and Km is 1.5, with little temperature dependence. The size and the polarity of microemulsions are explored. The synergistic effect of [C16mim] [Br] and CAHS is confirmed by surface tension and interface tension. A universal preparation method to form microemulsions by combining ionic liquids with zwitterionic betaine-type surfactants is provided and it play a pivotal role in broadening the potential uses of ILs in microemulsions.

High-resolution performance of pillar[6]arene functionalized with imidazolium ionic liquids for gas chromatography

Pillar[n]arenes (P[n]A, n = 5–10) have attracted much attention because of their highly symmetric pillar-shaped architecture with π-electron rich cavity. Nevertheless, the use of ionic liquid functionalized P[n]A in chromatography has not been reported up to data. This work reports the investigation of the imidazolium ionic liquids functionalized pillar[6]arene (P6A-C10-IM-C8[NTf2]) as the stationary phase for gas chromatography (GC). The statically coated P6A-C10-IM-C8[NTf2] column (0.25 mm i.d.) showed moderate polarity and high column efficiency of 4733 plates/m determined by n-dodecane at 120 °C (k = 2.29). Owing to its unique amphiphilic conformation, the P6A-C10-IM-C8[NTf2] showed good column inertness and resolving capability for a wide range of analytes and isomers. Particularly, the P6A-C10-IM-C8[NTf2] column exhibited distinctly advantageous performance for the challenging isomers of halogenated benzenes, benzaldehydes, phenols and anilines over the common commercial columns, namely 5% phenyl methyl polysiloxane (HP-5) and 35% phenyl methyl polysiloxane (HP-35). In addition, it exhibited good column repeatability and reproducibility with RSD values on the retention times less than 0.05% for run-to-run, 0.38% for day-to-day and 2.94% for column-to-column, respectively. This work demonstrates the promising future of ionic liquid P[n]A stationary phases for chromatographic separations.

Synergistic effects of melamine functionalized graphene oxide and imidazolium ionic liquid on the tribological performance and thermal stability of polyalphaolefin based hybrid nanolubricants

Tribological and thermophysical characteristics of a new hybrid nanolubricant that incorporates melamine functionalized graphene oxide (mGO) and imidazolium cation based ionic liquid (IL) in a polyalphaolefin (PAO-6) base oil have been investigated. Different formulations of nanolubricants with 0.05 wt%, 0.1 wt% nanosheets and 1 wt% ionic liquid were studied to examine the synergistic effects of surface functionalization and ionic liquid addition on the antifriction and antiwear properties of the PAO-6 base oil. Thermal stability studies involved Thermogravimetric analysis to analyze the oxidation onset and decomposition temperature of different formulatons at varying weight concentrations of nanoadditives. Anti-friction performance was quantified by the coefficient of friction (COF) reduction compared to neat lubricant. The highest reduction in COF was observed for 0.05 wt% mGO + 1 wt% IL with an outstanding 73.33% reduction followed by 0.05 wt% mGO and 0.05 wt% GO with 73% and 67% reduction respectively. Post-wear analysis of the wear scars was performed using 3D optical profiler, SEM micrographs, EDX elemental composition and Raman spectra. The highest reduction in wear depth was observed in the case of PAO-6 + 0.05% mGO with a value of 46.3% followed by a 39.9% reduction in the case of PAO-6 + 0.05% GO. The morphologies of samples containing both ionic liquid and nanosheets exhibited a much smoother surface with the absence of deep grooves and pits which was attributed to the formation of a strongly bonded tribofilm owing to the chemical interactions between ionic liquid capped nanosheets and metal substrate. Strong interfacial interactions also induced a significant increase in the thermal stability of the nanofluids. The maximum shift observed in the oxidation onset temperature compared to neat PAO-6 was 68◦C while the decomposition temperature increased by 61◦C. Due to their excellent friction, wear, and thermal properties, these hybrid nanofluids could be applied in various highly demanding industrial sectors such as automotive, machining operations, aerospace, thermal power plants and micro/nano-electromechanical systems.

Thermal hazard evaluation and risk assessment of 1-allyl-3-methylimidazole nitrate ionic liquid

Imidazole ionic liquids (ILs) have broad application prospects in batteries and other fields. Researching the thermal decomposition features of ILs holds paramount importance for the application in battery electrolyte. 1-allyl-3-methylimidazole nitrate ionic liquid (IL) as a new functional IL, and its related thermal decomposition properties are unknown. In this paper, the thermal decomposition peculiarities of 1-allyl-3-methylimidazole nitrate IL were systematically analyzed by thermogravimetric analyzer, differential scanning calorimetry, and accelerating rate calorimeter techniques, and the relevant thermodynamic parameters and thermal decomposition models were derived. In addition, 1-allyl-3-methylimidazole nitrate IL possesses strong thermal runaway characteristics and the risk of thermal runaway is also evaluated. The main gaseous products formed by the pyrolysis of 1-allyl-3-methylimidazole nitrate IL was detected and analyzed by thermogravimetry-Fourier transform infrared spectroscopy and thermogravimetric-photoionization mass spectrometry techniques. The results showed that flammable gas, toxic gas, and asphyxiating gas are formed during the pyrolysis of 1-allyl-3-methylimidazole nitrate IL. This study lays a theoretical foundation for the safe application and the formulation of corresponding safety protection measures of 1-allyl-3-methylimidazole nitrate IL.

Scrutinizing the antibacterial activity of poly (1‐vinyl‐3‐alkyl imidazolium) ionic liquids: experimental and computational approach

AbstractBackgroundAntimicrobial resistance has become a serious concern and threat to global health. This has triggered the need for the design of new antimicrobials. In this study, poly‐ionic liquid (PIL) homopolymers have been designed by varying the alkyl chain lengths to evaluate their pathogeneses against Gram‐positive (Staphylococcus aureus) and Gram‐negative bacteria (Escherichia coli).ResultsThe results demonstrated that the antimicrobial and antibiofilm activities depend on the alkyl chain length of PILs (C10 > C8 > C6). To support the experimental findings, in silico analyses were performed to explore the structural and functional information of bacterial RNA polymerase (RNAP) enzymes. A switch region was identified between RNAP β subunit (RpoB) and RNAP β' subunit (RpoC) with 1119 amino acids (aa) and 1504 (2–1505) aa, respectively. The docking analysis reflected the docking energies −5.313 kcal mol−1 for RNAP‐poly‐1‐vinyl‐3‐hexyl imidazolium complex, −4.634 kcal mol−1 for RNAP‐poly‐1‐vinyl‐3‐octyl imidazolium complex, and −3.456 kcal mol−1 for RNAP‐poly‐1‐vinyl‐3‐decyl imidazolium complex.ConclusionThe synthesized PIL samples exhibited antibacterial and antibiofilm activities against E. coli and S. aureus. However, the effect on E. coli was more prominent in comparison to S. aureus. The results indicated that both electrostatic interaction and hydrophobic effect played a vital role in enhancing the antibacterial as well as antibiofilm activities. In addition, in silico analysis identified the ‘switch region’ between RNAP β subunit (RpoB) and RNAP β subunit (RpoC). The novel target appeared to be a binding region for PILs and restricted the synthesis of bacterial RNA. It can be concluded that imidazolium‐based PILs can be used as safe antibacterial materials in the healthcare sector. © 2024 Society of Chemical Industry (SCI).

The Imidazolium Ionic Liquids Toxicity is Due to Their Effect on the Plasma Membrane

The Imidazolium Ionic Liquids Toxicity is Due to Their Effect on the Plasma Membrane

Influence of Ionic Liquid and Light Intensity on a Polymer Nanostructure Formed in Lyotropic Liquid Crystalline Templates.

Utilizing self-assembled lyotropic liquid crystal (LLC) templates with radical photopolymerization shows promise in controlling polymer structure on the nanometer scale This control of nanostructure allows tailoring and enhancement of material properties not attainable in traditional polymerization in applications including hydrogels and stimuli-responsive systems. However, thermodynamically driven phase separation between the polymer and LLC templates often hinders the control of local polymer order and resultant polymer properties. This study investigates an alternative method to control the hydrogel nanostructure and avoid phase separation using imidazolium ionic liquids (ILs) in the LLC template while modulating the light intensity used in photopolymerization. The addition of the IL improves the thermodynamic stability and enhances the polymerization rate in the LLC system. The degree of LLC nanostructure retention is increased by increasing light intensities during polymerization. In addition, intermediate concentrations of cross-linker allow a balance between phase stability and cross-linking to lock in LLC morphology. With enhanced retention, the maximum water uptake is significantly higher compared with isotropic controls. These results demonstrate a method to increase the structure on the nanometer scale of a polymer by combining the addition of ILs with the proper selection of light intensity and cross-link density that allows access to unique hydrogel properties. These templated polymers demonstrate enhanced swelling and a stimuli response that show promise in applications ranging from drug delivery to water remediation.

Impact of Ionic Liquid Functionalized ZrO2 Nanoparticles on Poly (stearyl methacrylate) Grafted Poly (vinylidene fluoride‐co‐hexafluoropropylene) Based Highly Conductive Gel Polymer Electrolytes for Lithium‐Metal Batteries

AbstractIn this study, an organic‐inorganic hybrid polymer membrane is successfully designed and developed by grafting stearyl methacrylate (SMA) side chains onto the backbone of the P(VDF‐HFP) copolymer followed by blending with varying amounts of imidazolium ionic liquids functionalized ZrO2 nanoparticles. Different microporous gel polymer electrolytes (MGPEs) are prepared by immersing the membranes into a LiTFSI salt‐dissolved ionic liquid electrolyte. The membranes′ crystallinity, surface morphology, porosity, and thermal stability are investigated using various characterization techniques. The copolymer membrane blended with 60 wt % functionalized nanoparticles exhibits the highest porosity of 64.5 %, which allows it to achieve a maximum electrolyte uptake of 387 wt %. That enables the corresponding MGPE to achieve the highest room temperature lithium ion conductivity of ~5.34×10−3 S cm−1 with a wide electrochemical stability window and good electrochemical stability against Li metal. Leveraging these advantageous characteristics, the lab‐scale truly solid‐state Li|MGPE|LiFePO4 and Li|MGPE|LiNi0.8Mn0.1Co0.1O2 cells demonstrate excellent rate capability and reversible cycling stability while maintaining high specific capacities (up to 154 and 172 mAh g−1, respectively, at 0.5 C) with >99.0 % coulombic efficiency over 100 cycles. Such exceptional interfacial compatibility with both low‐ and high‐voltage cathodes establishes the applicability of these newly developed MGPEs in next‐generation all‐solid‐state lithium‐metal batteries.

Cross-linked poly(vinyl alcohol)/citric acid electrospun fibers containing imidazolium ionic liquid with enhanced antiadhesive and antimicrobial properties

Patients in hospital environments are susceptible to bacterial colonization, which can lead to infections. In this study, electrospun fibers were manufactured using poly(vinyl alcohol) (PVA) crosslinked with citric acid (CA) and incorporating the ionic liquid (IL) 1-hexadecyl-3-methylimidazolium chloride (C16MImCl) to prevent microbial growth and biofilm formation. The presence of CA and IL reduced the surface tension of the PVA solution (12% w/v) from 52.07 mN/m to 35.84 mN/m. CA was introduced into PVA solutions, and the resulting fibers were thermally crosslinked through esterification between PVA hydroxyl groups and CA. X-ray photoelectron spectroscopy (XPS) confirmed the presence of IL on the fiber surfaces. The IL acted as a surfactant, imparting plasticity to the electrospun fibers and enhancing homogeneity and mechanical properties. Before crosslinking, the PVA/CA/IL fibers exhibited an elongation at break (%) of approximately 140%, a tensile strength of 5.3 MPa, and an elastic modulus of 18.2 MPa. After cross-linking, the elongation at break reduced to 86%, the tensile strength increased to 7.6 MPa, and the elastic modulus increased to 88 MPa. Mechanical measurements confirmed the thermal crosslinking of the fibers, primarily because of the increased elastic modulus. Adhesion and proliferation tests with Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) indicated reduced bacterial adhesion and growth on the PVA/CA/IL fibers. Antimicrobial assays further confirmed a 50.73% and 69.42% increase in bactericidal activity against S. aureus and P. aeruginosa, respectively. The PVA/CA/IL fibers exhibit promising potential for producing antimicrobial materials to prevent the attachment and proliferation of microbial strains on solid surfaces.

A novel phosphorus/nitrogen-containing vinyl imidazolium ionic liquid for improving flame retardancy and mechanical properties of vinyl ester resin, and its carbon fiber composites

In daily life, the application of vinyl ester resin (VER) and its carbon fiber composites is limited by their flame retardancy and mechanical properties. In this work, we synthesized an ionic liquid, VIDHP, from diethyl hydroxymethyl phosphate (DHP) and 1-vinylimidazole (VIM). VIDHP can not only cross-links with VER but also enhances the interaction between the resin and the carbon fiber. The flame retardancy and mechanical properties of VER and its carbon fiber composites were effectively improved by the addition of VIDHP. In particular, the addition of 15 wt% VIDHP increased the flexural strength and flexural modulus of the carbon fiber composites by 29.3 % and 42.4 %, while reducing the total heat release and total smoke release by 15.4 % and 18.4 %. The flame retardant mechanism of VIDHP was also investigated. This approach provides a new idea to improve the flame retardant and mechanical properties of VER and its carbon fiber composites.

Synthesis of imidazolium ionic liquid immobilized on magnetic mesoporous silica: A sorbent material in a green micro-solid phase extraction of multiclass pesticides in water

In this study, we synthesized an imidazolium ionic liquid immobilized on magnetic mesoporous silica (IL-MMS) and evaluated its performance as a sorbent material for a green micro-solid phase extraction (μ-SPE) of multiclass pesticides in water. The synthesized IL-MMS was characterized by various analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) analyses (N2 adsorption/desorption), Vibrating Sample Magnetometer (VSM), energy-dispersive spectroscopy (EDS) and Field emission scanning electron microscopy (FESEM). Our synthesized IL-MMS demonstrated excellent magnetic properties (31.5 emu/g), high surface area (1177.4 m2/g), proper pore size (⁓4.2 nm) and volume (1.80 cm3/g). Under optimized extraction conditions, the IL-MMS exhibited a high adsorption capacity for a variety of pesticides, including organophosphates, carbamates, and pyrethroids. The proposed μ-SPE method using IL-MMS showed good linearity (R2 > 0.99), low limits of detection (LODs) ranging from 0.04 to 1.63 ng/L, and suitable recovery rate was between 82.4% and 109.8% for different pesticides. In addition, the method also exhibited excellent reproducibility, with relative standard deviations (RSDs) of less than 8% for both intra and inter-day precision. In overall, the synthesized IL-MMS has proven to be a highly promising material for sorbent-based micro-solid phase extraction (μ-SPE) of multiclass pesticides in water. With its simple, efficient, and eco-friendly approach to pesticide analysis, this method shows great potential for future pesticide detection and monitoring efforts due to its sensitivity, accuracy, and adaptability to various environmental conditions.

Improving ruthenium nanoparticle physicochemical properties and chemotherapeutic efficacy by dual-encapsulating with new amphiphilic chitosan and imidazolium ionic liquid

This study introduces new amphiphilic low-molecular-weight chitosan (ALMC) and imidazolium ionic liquid (IIL) as encapsulating agents for in-situ ruthenium nanoparticles (RuNPs) synthesis, resulting in Ru-nanobicomposites (RNBCs: Ru/IIL, RNBC1; Ru-IIL/ALMC, RNBC2) with mean diameters of (2.16–5.19 nm). RNBCs display remarkable collodial stability with high ζ-potential values ((+39.95)–(+48.07) mV) and uniform size distribution with low polydispersity index values (0.23–0.21). In vitro experiments revealed that RNBCs had potent anti-cancer properties, with IC50 values indicating that they were more toxic to HepG2 cells (IC50 = 2.16 ± 0.17–9.12 ± 0.71 μg/ml) than CaCo-2 cells (IC50 = 0.61 ± 0.25–11.05 ± 0.48 μg/ml). Specifically, IIL and ALMC's dual-encapsulated RuNPs (RNBC2) could be a potential anticancer drug. RNBC2 increased intrinsic apoptotic markers P53 and Bax gene expression and inhibited Topo II, damaging liver cancer cells. These findings show that RuNPs' encapsulating materials affect their interactions with cancer cells and enhance their anticancer capabilities.

Structure-Dependence and Mechanistic Insights into the Piezoelectric Effect in Ionic Liquids.

We reported recently that two imidazolium room-temperature ionic liquids (RTILs) exhibit the direct piezoelectric effect (J. Phys. Chem. Lett., 2023, 14, 2731-2735). We have subsequently investigated several other RTILs with pyrrolidinium and imidazolium cations and tetrafluoroborate and bis(trifluoromethylsulfonyl)imide anions in an effort to gain insight into the generality and mechanism of the effect. All the RTILs studied exhibit the direct piezoelectric effect, with a magnitude (d33) and threshold force that depend on the structures of both the cation and anion. The structure-dependence and existence of a threshold force for the piezoelectric effect are consistent with a pressure-induced liquid-to-crystalline solid phase transition in the RTILs, and this is consistent with experimental X-ray diffraction data.

Insight of super-capacitive properties of flexible gel polymer electrolyte containing butyl imidazole ionic liquids with different anions based on PVDF-HFP

Insight of super-capacitive properties of flexible gel polymer electrolyte containing butyl imidazole ionic liquids with different anions based on PVDF-HFP

Cheap and efficient strategy for photocatalytic degradation of ionic liquids by La/Ce-codoped TiO2@PAM composites.

Ionic liquids are regarded as green solvents mainly due to their non-volatile and easy regeneration and recycling properties. However, ionic liquids have negative effects on the environment and human health, especially alkyl imidazole ionic liquids are more toxic than traditional organic solutions. Studies on the toxicology, ecotoxicology, and degradation of ionic liquids are rarely found in the literature. Here, we prepared the cheap La and Ce-codoped TiO2@PAM (polyacrylamide) composite microspheres with a simple procedure for the first time to degrade three kinds of imidazole ionic liquids with high efficiency. The experimental results show that the composite La (0.25%) and Ce (0.15%)-codoped TiO2@PAM composite microspheres with calcination temperature of 450 °C had a high photocatalytic activity for 1-butyl-3-methyl imidazolium hexafluorophosphate, 1-hexyl-3-methyl imidazolium hexafluorophosphate, and 1-octyl-3-methyl imidazolium hexafluorophosphate with the concentration of 10 mg/L. The photocatalysis degradation extent of the three ionic liquids is 97.4, 91.2, and 88.5% at 90 min. This work opened a new route for the simple preparation of cheap composite microspheres in the photocatalytic degradation of ionic liquids with a high efficiency.

Mechanically Tough Micellar Cubic Liquid‐Crystalline Polymer Electrolytes for Electromechanical Actuators

AbstractThis study presents a novel micellar cubic ionic liquid‐crystalline polymer electrolyte, featuring an alignment‐free spherical structure with unimpeded 3D ionic pathways, aimed at enhancing the performance of an ionic electroactive polymer actuator. The development involved creating a mechanically tough and high ion‐conductive cubic polymer film through the self‐assembly of a wedge‐shaped vinyl imidazolium salt and an imidazolium ionic liquid, followed by in situ photopolymerization. The 300 µm‐thick‐trilayer films, consisting of the cubic polymer electrolyte sandwiched between poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) electrodes, exhibit remarkable capabilities. These include bearing substantial loads of 4 g with a high blocking force under a DC voltage of 2 V, achieving a high bending strain of 0.63% under a low input voltage (±2 V, 0.1 Hz), and boasting a maximum response frequency of 70 Hz. These properties position the material for potential applications in soft robots and tactile sensing devices.

The influence of ionic liquids with heterocyclic cations on CO2 hydrates formation

Kinetic characteristics of CO2 hydrates formation in the presence of eight ionic liquids with heterocyclic cations and [PF6]- anion were experimentally investigated here. It is found that the imidazolium ionic liquids with short substituted alkyl chains can inhibit CO2 hydrates formation. Increasing the alkyl chain length can alleviate the nucleation inhibition effect, and 1-hexadecyl-3-methylimidazolium hexafluorophosphate([C16mim][PF6]) with a concentration of 10 wt% even shows a slight promotion effect comparing to the pure water. In contrast, adding pyrrolidinium, piperidinium and pyridinium ionic liquids increases the nucleation temperatures, shortens the induction times and enhances the CO2 consumption. Based on DFT calculations and MD simulations, it is inferred that the strong binding energy between H2O and 1-ethyl-imidazolium hexafluorophosphate([Emim][PF6]) plays a main role on its inhibition behavior during CO2 hydrates formation. The H2O-H2O RDF curves of N-butyl pyridinium hexafluorophosphate([OPy][PF6]), N-butyl-N-methylpiperidinium hexafluorophosphate([PP14][PF6]) and N-butyl-N-methylpyrrolidinium hexafluorophosphate([PY14][PF6]) aqueous systems exhibit three peaks which become intensified and narrow with time, while [Emim][PF6]-containing system only has a single peak due to its strong interaction with water and thus inhibits the water-water attraction. In addition, RDF peaks of H2O–[PF6]- become weak gradually with time, implying that the anion [PF6]- does not engage in the structures of water cages.

Ionic Liquid‐Mediated Dynamic Polymerization for Facile Aqueous‐Phase Synthesis of Enzyme‐Covalent Organic Framework Biocatalysts

AbstractUtilizing covalent organic framework (COF) as a hypotoxic and porous scaffold to encapsulate enzyme (enzyme@COF) has inspired numerous interests at the intersection of chemistry, materials, and biological science. In this study, we report a convenient scheme for one‐step, aqueous‐phase synthesis of highly crystalline enzyme@COF biocatalysts. This facile approach relies on an ionic liquid (2 μL of imidazolium ionic liquid)‐mediated dynamic polymerization mechanism, which can facilitate the in situ assembly of enzyme@COF under mild conditions. This green strategy is adaptive to synthesize different biocatalysts with highly crystalline COF “exoskeleton”, as well evidenced by the low‐dose cryo‐EM and other characterizations. Attributing to the rigorous sieving effect of crystalline COF pore, the hosted lipase shows non‐native selectivity for aliphatic acid hydrolysis. In addition, the highly crystalline linkage affords COF “exoskeleton” with higher photocatalytic activity for in situ production of H2O2, enabling us to construct a self‐cascading photo‐enzyme coupled reactor for pollutants degradation, with a 2.63‐fold degradation rate as the poorly crystalline photo‐enzyme reactor. This work showcases the great potentials of employing green and trace amounts of ionic liquid for one‐step synthesis of crystalline enzyme@COF biocatalysts, and emphasizes the feasibility of diversifying enzyme functions by integrating the reticular chemistry of a COF.

Ionic Liquid-Mediated Dynamic Polymerization for Facile Aqueous-Phase Synthesis of Enzyme-Covalent Organic Framework Biocatalysts.

Utilizing covalent organic framework (COF) as a hypotoxic and porous scaffold to encapsulate enzyme (enzyme@COF) has inspired numerous interests at the intersection of chemistry, materials, and biological science. In this study, we report a convenient scheme for one-step, aqueous-phase synthesis of highly crystalline enzyme@COF biocatalysts. This facile approach relies on an ionic liquid (2 μL of imidazolium ionic liquid)-mediated dynamic polymerization mechanism, which can facilitate the in situ assembly of enzyme@COF under mild conditions. This green strategy is adaptive to synthesize different biocatalysts with highly crystalline COF "exoskeleton", as well evidenced by the low-dose cryo-EM and other characterizations. Attributing to the rigorous sieving effect of crystalline COF pore, the hosted lipase shows non-native selectivity for aliphatic acid hydrolysis. In addition, the highly crystalline linkage affords COF "exoskeleton" with higher photocatalytic activity for in situ production of H2 O2 , enabling us to construct a self-cascading photo-enzyme coupled reactor for pollutants degradation, with a 2.63-fold degradation rate as the poorly crystalline photo-enzyme reactor. This work showcases the great potentials of employing green and trace amounts of ionic liquid for one-step synthesis of crystalline enzyme@COF biocatalysts, and emphasizes the feasibility of diversifying enzyme functions by integrating the reticular chemistry of a COF.

Study on association and thermal stability of binary imidazolium ionic liquid mixtures

Ionic liquid (IL) mixtures with specific properties can be designed by the combination of different ionic liquids (ILs), but there are few studies on the physicochemical properties of IL mixtures with different ratios. Thus, this work explores the association and thermal stability of binary imidazolium IL mixtures. In particular, the physicochemical properties of binary IL mixtures at different ratios were investigated. Four different ILs, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1-butyl-3-methylimidazolium nitrate ([BMIM][NO3]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TFO]), and 1-butyl-3-methyl-imidazolium trifluoroacetate ([BMIM][CF3COO]), were selected as the parent salts to form the different binary imidazolium IL mixtures. These IL mixtures were tested at different temperatures (25, 30, 35, 40, 45, and 50 °C) and ratios (1:9, 3:7, 5:5, 7:3, and 9:1) by viscometer, conductivity meter, and then by isothermal thermogravimetric analysis in the temperature rise range of 30–500 °C. It was found that the increase in temperature decreased the association of IL mixtures, thus destroying the association behavior between the parent salts. Accordingly, different ratios of the parent salts had no significant effect on the thermal stability of some IL mixtures. Moreover, the results showed that smaller anions were more likely to combine with cations to form ion clusters or ion pairs, enhancing the association of binary IL mixtures. Thus, it increased the thermal stability of IL mixtures.