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The electrowetting behavior of ionic liquid significantly promotes microfluidic technology due to the advantage of manipulation of ionic liquid without additional mechanical parts. Recently, a novel micro-valve that shows good prospects was proposed by MacArthur et al. based on the permeation of ionic liquid under electric field. Inspired by their work, the permeation process of ionic liquid (EMIM-Im) droplets actuated by electrowetting was investigated in this work using molecular dynamics simulation. The wettability of substrate, electric field strength and electric field polarity were varied to investigate their influences. On the substrate side, results showed that the hydrophilic substrates tend to stretch and adsorb the droplet and hence hinder the permeation process, whereas the hydrophobic substrates facilitate permeation due to their low attraction for liquid. Particularly, super hydrophilic substrates should be avoided in practice, because their strong adsorption effects will override the electric field effects and disable the permeation process. On the electric field side, results showed that increased electric field strength enhances the permeation, but varying electric field polarity will result in an asymmetric permeation behavior, which was found to be the result of the different evaporation rate of the ion species that ultimately caused a non-charge-neutral droplet. Our investigation then uncovered the two critical roles of the electric field: elongating the droplet and providing the driving force for the permeation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

As an acid gas, sulfur dioxide (SO 2 ) has caused serious pollution to the environment. Therefore, SO 2 capture is crucial. The silica-based porous ionic liquid possesses not only the porosity and high specific surface area of hollow silica, but also the fluidity of the liquid. The absorption mechanism of SO 2 absorption by porous ionic liquids through density functional theory (DFT) was systematically studied in this paper. First six kinds of absorption sites were predicted, and then various analyses such as structure, energy, and electrostatic potential analysis (ESP) were employed after optimization. The results show that SO 2 has the strongest adsorptive interaction between the canopy and the silica sphere. In addition, the main force between the porous ionic liquid and SO 2 is hydrogen bonding and π-hole bonding. Finally, by increasing the degree of polymerization of the canopy, that is, increasing the number of ether groups, will be beneficial to the absorption of SO 2 ., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Carbon dioxide (CO 2 ) is one of the main factors leading to the greenhouse effect, so the capture of CO 2 gas is currently a hot spot of research. Hollow silica-based porous ionic liquids (HS-liquids) are porous liquids containing cavities that are not only fluid but also have a high specific surface area and were used for the capture of CO 2 . However, the mechanism of CO 2 absorption by HS-liquids has not been studied. In this work, the mechanism of CO 2 absorption by HS-liquids was systematic studied by density functional theory (DFT). First, five possible models for absorbing CO 2 in HS-liquids were constructed and optimized. The interaction energies between HS-liquids and CO 2 at different sites were obtained. Moreover, the effects of HS-liquids with different degrees of polymerization of polyethylene glycol and different alkyl chain lengths on CO 2 absorption were also investigated. Results show that the strongest absorption site locates near the polyethylene glycol unit. Then, the electrostatic potential (ESP) and reduced density gradient (RDG) methods were employed to further understand the interaction nature between them. The results show that hydrogen bonding dominates the weak interaction between the HS-liquid and CO 2 ., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

[Display omitted] • An OCNR method has been first proposed for the controllable synthesis of functionalized PPILs. • The protic ion pairs play a crucial role in the formation of PPILs with low viscosity. • The PPILs possess excellent extractive capacity due to the rapid mass transfer offering enough electrons for DBT. • The primary driving forces for the extraction of DBT are the interactions of C H·π in protic ion pairs sites and C H···O in HS sites. Porous ionic liquids (PILs) offer a distinctive combination of liquid-like fluidity and solid porosity, making them well-suited for various applications including separation, catalysis, and energy storage. Nevertheless, the design limitations and complex synthesis processes have hindered the development of PILs. Here, the one-step coupling neutralization reaction (OCNR) method has been first proposed for the controllable synthesis of functionalized protic porous ionic liquids (PPILs). Specifically, three types of PPILs have been synthesized based on tuning the position of the corona amino functional groups. The results indicate the crucial role of protic ion pairs in the formation of pure liquid PPILs with low viscosity. The extraction efficiency has obviously increased after introducing the porous materials from 38.5% to 51.9%. The results showed PPILs play good extraction-adsorption coupled desulfurization (EADS) performance. The density functional theory (DFT) results show that both the protic ion pairs and the porous structure have significant roles in EADS, with the former offering C H···π interactions, while the latter provides hydrogen bonding (C H···O) interactions. Ultimately, the strategy simplifies the synthesis process, providing a new idea for the directional design of low-viscosity PILs with specific functions. [ABSTRACT FROM AUTHOR]

Concentrated aqueous solutions with high conductivity have been proven difficult to be stably electrosprayed mainly due to their large surface tension, which will easily trigger air discharge. The ionic liquid with lower surface tension is involatile, viscous, and highly conductive and can easily achieve stable electrospray. This paper presents a more convenient method to ionize the concentrated aqueous solution than the previous attempts and proves the feasibility of coaxially electrospraying two highly conductive liquids (∼1 S/m). Our method utilizes a coaxial capillary to coat the highly conducting concentrated sodium chloride (NaCl) aqueous solution (0.67 S/m) with a thin layer of immiscible ionic liquid to form a compound cone and achieve the stable coaxial electrospray. The compound cone remains static at a suitable flow rate (0.1–1 nl/s) of the ionic liquid. At a higher or lower flow rate, the compound cone elongates or shrinks and eventually vibrates. Due to the high conductivity of both liquids, the spray current does not follow the current scaling law. The spray current is mostly dominated by the NaCl solution and counterintuitively decreases as the flow rate of the ionic liquid increases due to the frequent vibration of the compound cone. The highly conducting thin layer of the ionic liquid is the key to achieving stable coaxial electrospray. It lowers the surface tension of the compound cone and shields the external electric field acting at the inner aqueous solution; thus, the air discharge of the aqueous solution is suppressed, and the stable compound cone can be formed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel type of ionanofluids were successfully constructed for ECODS. • Ionanofluids displays high selectivity and recyclability for desulfurization. • The synergistic effect between Mo-MOF and ionic liquids was verified. Ionanofluids as newly introduced types of nanofluids with promising potential for diverse applications are created through dispersing nanoparticles into ionic liquids. Ionanofluids capitalize on both the catalytic ability of nanoparticles and the rapid mass transfer along with the extraction performance of ionic liquids. Herein, a novel kind of ionanofluids (denoted Mo-INFs) was constructed by employing a Mo-MOF as the nanoparticle and an imidazole-based ionic liquid ([BDIM][NTF 2 ]) as the base fluid. As the efficiency of Mo-INFs (97.9 %) surpassed the summarized efficiency of Mo-MOF and [BDIM][NTF 2 ], a synergistic effect between the Mo-MOF moiety and the [BDIM][NTF 2 ] moiety in Mo-INFs did exist. Under optimum reaction conditions, the Mo-INFs exhibited remarkable selectivity and recyclability in desulfurization. A possible desulfurization mechanism was proposed that aromatic sulfur compounds in the model oil phase were initially extracted into ionanofluids phase via C-H···π and π···π interactions and subsequently oxidized by peroxo species that formed in the presence of H 2 O 2 and Mo-MOF. [ABSTRACT FROM AUTHOR]

Electrospray thrusters with small size, high precision specific impulse, low power consumption are the most recommended propulsive equipments for micro-nano satellites. Molecular dynamics simulation is able to be used to predict the fundamental physics of electrospray and evaluate the propulsive performance. However, the accuracy of molecular dynamics simulation results critically depends on the accuracy of the interaction potential models used. Therefore, the present paper discusses the effect of different interaction potential models on the molecular dynamics simulations of electrospray thrusters with ionic liquid 1-ethyl-3-methyl-imidazolium tetrafluoroborate. The reduced charge all-atoms model, full charge all-atoms model, effective-force coarse-grained model and Merlet coarse-grained model reported in the literature are used for comparison, and comparison is also made to experimental data to elucidate which interaction potential model might be the most realistic. The process of Taylor cone formation, electrospray currents, energy characteristics and velocity distribution are analyzed under varying operating conditions. Our calculations indicate that the reduced charge all-atoms model is the most accurate model for molecular dynamics simulation of electrospray. In contrast, the coarse-grained models fail to reveal the energy characteristics. The full charge all-atoms model is not able to characterize the velocity characteristics. The full charge all-atoms model and coarse-grained models underestimate and overestimate the propulsive performance respectively. It is also found that the energy characteristics and velocity distribution of particles within the Taylor cone are almost unchanged with varying operating conditions. Image 1 • Reduced charge all-atoms model provides most reliable evaluation of electrospray behavior. • Particles properties within Taylor cone almost unchanged with varying operating conditions. • The weaker coulombic potential energy, the easier atomization of ionic liquid. • Mass flow rate affects velocity distribution more strongly than other operating parameters. [ABSTRACT FROM AUTHOR]

Porous ionic liquids (PILs) are an emerging class of materials that possess the porosity of solids and the fluidity of liquids, which have shown great potential in separation. Herein, a novel kind of silica-based porous ionic liquids (OS-PIL) functionalized with quaternary ammonium salt was successfully synthesized to remove the dibenzothiophene (DBT) in the model fuel. The OS-PIL exhibit high extraction activity and its Nernst partition coefficient could reach up to 4.22. The experimental results indicated that a synergistic effect between porous materials and ionic liquids as well as the multiple sites in quaternary ammonium salt greatly contributed to the high extractive desulfurization efficiency. Moreover, density functional theory (DFT) calculations and spectroscopic investigations were employed to gain in-depth insights into the extraction mechanism. The results demonstrated that the porous structure and ion pair of OS-PIL exhibit stronger interaction for DBT, in which the C-H···π is dominant. These kinds of PILs with highly specific surface areas and multiple active sites will have good application prospects in the field of extractive desulfurization. [Display omitted] • OS-PIL was designed as an extractant for desulfurization. • The synergistic effect resulted in the OS-PIL showing high extraction activity. • The extractive mechanism has been thoroughly investigated by experimental and theoretical methods. • C-H···π is the major weak interaction between OS-PIL and DBT. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crown ethers and K+ are complexed mainly by electrostatic interaction rather than coordination. • Compared with N 2 , PILs tend to absorb CO 2. • Absorbing 4 equivalents of CO 2 is unlikely for one POC. Porous liquids, a new class of materials, containing solid pores and liquid properties, have greatly aroused attention. In terms of gas absorption, porous liquids exhibit excellent advantages. Nevertheless, a variety of reports still lack the understanding of its absorption mechanism at the molecular level. Herein, we have figured out the factors contributing to the formation of porous liquids made of porous organic cages that can be dissolved in the crown ether, and the absorption mechanism of carbon dioxide, as well as CO 2 /N 2 selectivity. Through charge and Wiberg index analysis, the results show that crown ethers can interact with alkali metals to form alkali metal complexes by ion–dipole interactions, the dominant driving force of which is electrostatic interaction rather than coordination effect. Besides, the metal complexes should be regarded as a whole entity, which increases the steric hindrance of the cations and greatly reduces the probability of the crown ether blocking the cavity. The porous organic cage does provide unoccupied pores for gas storage. Furthermore, compared with N 2 , cages prefer to absorb CO 2 mainly through hydrogen bonding. It is hoped that this work can facilitate the design and synthesis of porous liquids for gas absorption and selectivity. [ABSTRACT FROM AUTHOR]

• MD simulation of electrospray with a hybrid emitter for the first time. • The hybrid emitter operates at a pure ion mode with a low flow rate. • The hybrid emitter transits to the capillary emission mode at a high flow rate. • Particles with charge below the Rayleigh limit predict the existence of droplets. Electrospray thrusters are most suitable for micro-nano satellites in advantage of small size, low power consumption and high specific impulse. However, conventional electrospray thrusters with capillary emitters operate at single mode with limited range of thrust. In order to expand range of thrust, novel electrospray thrusters with hybrid emitters which are capable of operating at dual-modes are recommended. Molecular dynamics simulation is used to study the behaviors of the novel electrospray thruster in this work, using EMIM-Tf2N as propellant. Electrospray behaviors for the capillary emitter and the hybrid emitter are compared at the same operating conditions, showing that droplets are more easily emitted from the capillary emitter. For the hybrid emitter, the externally-wetted emission mode is displayed at a low flow rate. Only ions are emitted from the hybrid emitter because of the stronger electric field and larger hydraulic impedance. Meanwhile the change in range of mean diameter and charge to mass ratio of particles are relatively small as compared to the capillary emitter. But the hybrid emitter transits into a capillary emission mode at a high flow rate. Furthermore, analysis of particle charge shows that if there exist particles with charge below the Rayleigh limit, droplets can be produced in electrospray beam. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • UiO-66-BAPILs were designed and fabricated for oxidative desulfurization. • The permanent cavity in UiO-66-BAPILs was validated by gas uptake experiments and molecular size simulations. • UiO-66-BAPILs exhibited higher catalytic activity than the two components. • The mechanism was in detail studied by experiments and theoretical calculations. Porous ionic liquids have been highlighted with special interest for their desirable catalytic activity and extraction properties. Herein, bifunctional porous ionic liquids (denoted UiO-66-BAPILs) were synthesized by dispersing UiO-66 into a pyridinium-based Brønsted acidic ionic liquid ([BSPy][CF 3 SO 3 ]) for oxidative desulfurization. The permanent cavity of UiO-66 moiety in UiO-66-BAPILs was validated as well-preserved by the SO 2 uptake experiments and molecular size simulations. Under the optimum reaction conditions, the sulfur removal could reach up to 99.5% with hydrogen peroxide as the oxidant. Additionally, bifunctional UiO-66-BAPILs were deemed as both extractants and catalysts during the reaction. A possible mechanism has been proposed that UiO-66-BAPILs extract the aromatic sulfur compounds via π···π interactions and C-H···π interactions and meanwhile oxidize them with peroxysulfonic acids and •OH radicals. These findings will open up new avenues to facilitate the catalytic oxidation performance by constructing bifunctional Brønsted acidic porous ionic liquids. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel type of PILs has been fabricated. • PILs integrate the permanent pores of porous solids with the exceptional properties of ILs. • PILs possess high activity and selectivity for the DBT oxidation. • IL moiety serves as an extractant to enrich DBT and creates an electrostatic solvent effect. • UiO-66 moiety serves as a catalysis to handily catalyze the ODS reaction. Developing a highly efficient strategy for the stabilization of the solid-liquid interface is a persistent pursuit for researchers. Herein, porous ionic liquids based on UiO-66 (Zr) porous materials were synthesized and applied to the selective desulfurization catalysis, which integrates the permanent pores of porous solids with the exceptional properties of ionic liquids. Results show that porous ionic liquids possess high activity and selectivity for dibenzothiophene. Experimental analysis and density functional theory calculations revealed that the ionic liquids moiety served as an extractant to enrich dibenzothiophene into the porous ionic liquids phase through the π···π and C H···π interactions. Additionally, the electrostatic solvent effect in the porous ionic liquids contributes to the stabilization solid-liquid interface, which was favorable for UiO-66 moiety to catalytically activate hydrogen peroxide (H 2 O 2) to generate ·OH radicals, and subsequently oxidized dibenzothiophene to the corresponding sulfone. It is hoped that the development of porous ionic liquids could pave a new route to the stabilization of the solid-liquid interface for catalytic oxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of novel and stable PILs were constructed for ECODS. • The permanent porosity of PILs was confirmed by gas uptake and molecular simulation. • PILs exhibited high catalytic activity for oxidative desulfurization. • The synergistic effect between UiO-66 moiety and IL moiety was verified. • The mechanism of ECODS systems was systematically studied and proposed. Porous ionic liquids are a novel category media that possesses the catalytic activity of porous solids and the extraction property of ionic liquids. Herein, a new type of porous ionic liquids (denoted as UiO-66-T3PILs) was fabricated by employing UiO-66(Zr) as the pore generator and the ionic liquid ([P 6,6,6,14 ][NTF 2 ]) as the size-excluded solvent for extraction coupled catalytic oxidative desulfurization (ECODS) using hydrogen peroxide (H 2 O 2 , 30 wt%) as an oxidant. Furthermore, several significant reaction parameters such as UiO-66 loading in porous ionic liquids, reaction temperatures, molar ratio of H 2 O 2 /DBT and sulfide species as well as recyclability were investigated in detail. As UiO-66-T3PILs exhibited higher efficiency (95.3%) than the summarized efficiency of UiO-66 and [P 6,6,6,14 ][NTF 2 ], there did exist a synergistic effect between the UiO-66(Zr) moiety and the ionic liquid moiety in UiO-66-T3PILs. With the assistance of density functional theory calculations, a possible mechanism was proposed that aromatic sulfur compounds in the oil phase were first extracted into ionic liquids moiety phase via C-H···π interactions and then rapidly oxidized by OH radicals in the presence of the UiO-66 moiety. This work will pave the way for the rational design of novel porous ionic liquids towards catalysis. [ABSTRACT FROM AUTHOR]

• CAB-PILs showed excellent catalysis performance for CO 2 cycloaddition reaction. • Cycloaddition mechanism were investigated by experimental and DFT methods. • The Lewis base site of CAB-PILs is the CO2 adsorption center. • Lewis base and Bronsted acid sites have a synergistic effect. Conjugate acid-base bi-functional PILs (CAB-PILs) with carboxylate and carboxyl branches were synthesized and used as catalysts for the cycloaddition reaction of glycidol with CO 2. Two functional ionic monomers, 3-(carboxymethyl)-1-vinyl-1H-imidazol-3-ium chloride (CEImCl) and 2-(1-vinyl-1H-imidazol-3-ium-3-yl) acetate (CCIm), were introduced into the CAB-PILs skeleton. In this case, we proved the excellent characteristics of the catalyst containing both Lewis base and Bronsted acid sites for converting CO 2 to cyclic carbonate under mild conditions. The catalyst showed good reusability and remained excellent activity after five reaction cycles. Combined with XPS, FTIR and DFT calculations, it is proved that the CCIm ionic monomer not only play the role of CO 2 absorption center, but also has synergistic effect with CEImCl in CAB-PILs to promote cycloaddition reaction. [ABSTRACT FROM AUTHOR]

• MD simulation of electrospray with mixed ionic liquids for the first time. • Mixing of ionic liquids changes the emission mode of electrospray. • Mixing of ionic liquids reduces onset voltage and increases the stability of electrospray emission. • Simple mass ratio empirical approach underestimates electrospray propulsive performance. Micro-propulsion devices based on electrospray have advantages of high specific impulse, high precision and compact structure, and are able to meet the requirements of gravitational wave detection and other drag-free spacecrafts for micro-propulsion system. For electrospray thrusters, ionic liquid is the preferred propellant because of its low volatility, high electrical conductivity and thermal stability. Most of the studies presented today focus on single ionic liquid, while the properties of single ionic liquid are certain, which leads to a limitation of electrospray characteristics and hence propulsion performance. Mixing different kinds of ionic liquids broadens the properties of ionic liquids, and thus adjusts the characteristics of electrospray to meet the requirements of diversified space missions. In this paper, the effects of mixing two typical ionic liquids, 1-ethyltrimethylimidazole dicyanamide (EMIM-N(CN)2) and 1‑butyl‑trimethylimidazolium hexafluorophosphate (BMIM-PF6), on propellant properties and electrospray characteristics are investigated by molecular dynamics simulation and validated by comparing with experimental data. The result shows that the mixed ionic liquid changes the emission mode of electrospray thruster. Compared with BMIM-PF6, the specific impulse and thrust for the 50:50 (by mass) mixture increases by more than half of the difference between the two before mixing. In addition, the analysis shows that the range of extrusion voltage is widened by adjusting the mixing ratios to meet the mission requirements for certain specific impulse and thrust. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel and stable porous ionic liquids have been constructed. • π-electron-strengthening effect was formed between m-BN and [BPy][FeCl 4 ]. • The sulfur removal of the extractant correlates well with its porous structure. • Ultra-deep removal of dibenzothiophene can be achieved by m-BN-PIL extractant. Fe-based ionic liquids (ILs) exhibit a potential application in extractive desulfurization (EDS) of fuel oil, but struggle from the relatively low sulfur removal in a single extraction. In this work, a new type of porous ionic liquid (m-BN-PIL) was engineered by employing butylpyridinium tetrachloroferrate ([BPy][FeCl 4 ]) as an organic guest and microporous boron nitride (m-BN) as the porous framework. The formation of porous ionic liquid (PIL) promotes electron transport between [BPy][FeCl 4 ] and m-BN, hence enhancing electron densities of pyridinium ring cation ([BPy]+) and boosting m-BN dispersion, which favors the exposure of extraction sites. Furthermore, molecular size simulation and gas absorption experiments have validated the permanent porosity of m-BN-PIL, as has significantly improved mass transfer capacity when compared to pure [BPy][FeCl 4 ]. Both factors induce a significantly promoted EDS performance. Further characterizations verify that the m-BN-PIL remains stable during the extraction process. With m-BN-PIL as an extractant, 59.2 % and 61.8 % desulfurization performances can be achieved over dibenzothiophene (DBT) and 4-methyldibenzothiophene (4-MDBT) under the optimized extraction conditions, respectively. Especially, after four stepwise extraction processes, the extraction efficiency over DBT is high at 98.2 %, achieving deep desulfurization of fuel oil. This study presents a versatile strategy for designing high-performance EDS extractants by constructing strong electronic interactions between ILs and porous frameworks via dispersing m-BN within [BPy][FeCl 4 ]. [ABSTRACT FROM AUTHOR]