Green Energy&Environment

2020, 5(2) doi: 10.1016/j.gee.2020.05.008

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Innovating ionic liquids as repairable electronics for liquid robots

Jianji Wang

2020, 5(2): 122-123. doi: 10.1016/j.gee.2020.04.005

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When I read the paper of “Crystal-Confined Freestanding Ionic Liquids for Reconfigurable and Repairable Electronics” that was published on Nature Communications (Nat. Commun. 2019, 10, 547), I felt excited as it led to a new application of ionic liquids in addition to the enormous studies on chemical synthesis, catalysis, gas adsorption, processing biomass, and electrochemistry. This paper intended to mimic the liquid robot which was a classic character in the famous movie of Terminator 2: Judgment Day. The authors successfully exploited an approach to overcome the leakage problem of ionic liquids in the absence of encapsulation layers. It seems that ionic liquids would be one of the promising materials for green electronics with less production of electronic waste. In these regards, I would be delighted to write a highlight for this innovative work and hopefully it may raise more interests in the areas of ionic liquids.

Efficient Knoevenagel condensation catalyzed by imidazole-based halogen-free deep eutectic solvent at room temperature

Hao Qin, Yishan Zhou, Qian Zeng, Hongye Cheng, Lifang Chen, Bingjian Zhang, Zhiwen Qi

2020, 5(2): 124-129. doi: 10.1016/j.gee.2019.11.002

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For the first time, we employed the halogen-free deep eutectic solvent (DES) into the Knoevenagel condensation between aromatic aldehydes and active methylene compounds at room temperature. The DESs [3Im:PTSA] and [4Im:PTSA] were prepared by imidazole (Im) andp-toluenesulfonic acid (PTSA), which were experimentally screened from a series of organic acids with imidazole. α, β-Unsaturated carbonyl compounds were obtained in good to excellent yields under solvent-free conditions with fast reaction rate. These two DESs can be reused for multiple times with no loss of catalytic activity.

Dialkyl imidazolium acetate ionosilica as efficient and recyclable organocatalyst for cyanosilylation reactions of ketones

Thanh Tran Duy, Alysson Duarte Rodrigues, Giang Vo-Thanh, Peter Hesemann

2020, 5(2): 130-137. doi: 10.1016/j.gee.2020.03.005

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We report new heterogeneous organocatalyst based on silica hybrid supported N-heterocyclic carbene (NHC-) species. The organocatalyst is formed from an imidazolium iodide based ionosilica material, followed by iodide/acetate anion exchange. The imidazolium acetate generates the organocatalytic carbene via partial deprotonation of the imidazolium ring in situ. As monitored via EDX, solid state NMR and ion chromatography measurements, the iodide/acetate exchange involving the imidazolium ionosilica material took place only in small extent. Despite the fact that the exchanged material contains only a very small amount of acetate, we observed good catalytic activity and recyclability in cyanosilylation reactions of ketones with trimethylsilyl cyanide. The versatility of the catalyst was highlighted via reaction with several substrates, yielding the corresponding cyanohydrins in good yields. In recycling experiments, the material showed decreasing catalytic activity starting from the third reaction cycle, but high catalytic activity can be regenerated via another acetate treatment. Our work is important as it highlights the possibility to combine carbene chemistry and silica, which are antagonistic at a first glance. We show that imidazolium acetate based ionosilicas are therefore heterogeneous ‘proto-carbenes’, and that there is no need to form strongly basic silica supported NHCs to obtain heterogeneous NHC-organocatalysts. This work therefore opens the route towards heterogeneous and re-usable NHC-organocatalysts from supported ionic liquid imidazolium acetates.

Swelling acidic poly(ionic liquid)s as efficient catalysts for the esterification of cyclohexene and formic acid

Xin Wang, Sanguan Ma, Bihua Chen, Jingshun Zhang, Yongya Zhang, Guohua Gao

2020, 5(2): 138-146. doi: 10.1016/j.gee.2020.04.013

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Acidic poly(ionic liquid)s (PILs) with swelling ability were synthesized by free radical copolymerization of N-vinylimidazolium ionic liquids, divinylbenzene (DVB) and sodium acrylate (NaAA), and further acidification by sulfuric acid. The swelling ability of acidic PILs was greatly affected by cross-linker content and chain length of 3-alkyl-substituents on imidazolium. Cross-linked network structures could be observed from the cryogenic scanning electron microscopy (cryo-SEM) images of the swollen acidic PILs in formic acid. Acidic PILs with network structures in swollen state exhibited excellent activities in the esterification of cyclohexene and formic acid, and the catalytic activities were in positive correlation with their swelling abilities. Acidic PIL with 3-octyl-substituent and 2.5 mol% DVB (PIL-C8-2.5DVB-HSO₄) had the highest swelling ability in formic acid and exhibited comparable catalytic activities with homogeneous catalysts such as sulfuric acid and p-toluenesulfonic acid.

Highly efficient synthesis of 1-methoxy-2-propanol using ionic liquid catalysts in a micro-tubular circulating reactor

Yu-Mei Liu, Yan Zhou, Wen-Qiang Gong, Zhang-Min Li, Chao-Li Wang, Duan-Jian Tao

2020, 5(2): 147-153. doi: 10.1016/j.gee.2019.09.001

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The catalysis of ionic liquids (ILs) in the traditional stirred reactor suffers from insufficient mass and heat transfer, which always needs a long reaction time and results in a low reaction rate. In this work, highly efficient synthesis of 1-methoxy-2-propanol via the alcoholysis reaction of propylene oxide (PO) with methanol was proposed and achieved by the combination of micro-tubular circulating reactor with the IL [N₄₄₄₄][Buty] catalyst. Compared with the stirred reactor, the rate of alcoholysis reaction in a micro-tubular circulating reactor was found to be significantly improved. The reaction time was remarkably shortened to 20 min from 180 min as well as the yield of 1-methoxy-2-propanol reached 92%. Moreover, the kinetic study further demonstrated that the main reaction rate to 1-methoxy-2-propanol (K₁) was about 20 times larger than the side reaction rate to byproduct 2-methoxy-1-propanol (K₂) in the temperature range of 363–383 K. Such combination of micro-tubular circulating reactor with IL catalysts is believed to be a class of effective process intensification technique for highly efficient synthesis of 1-methoxy-2-propanol.

A bifunctional and recyclable catalyst: Amine and ionic liquid grafting on MOFs for the one-pot synthesis of N-aryl oxazolidin-2-ones

Siying Chong, Tongtong Wang, Haijun Zhong, Lingfei Xu, Hailong Xu, Zhongwu Lv, Min Ji

2020, 5(2): 154-165. doi: 10.1016/j.gee.2020.04.001

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A bifunctional heterogeneous catalyst was designed and synthesized, denoted DMEDA/IL–NH₂-MIL-101. The structure and physical-chemical characterization of DMEDA/IL–NH₂-MIL-101 and its precursors were characterized by SEM, N₂ adsorption-desorption, XPS, FT-IR, PXRD, elemental analysis, and TGA techniques. The date showed that the two catalytic components of N, N-dimethylethylenediamine (DMEDA) and 1-butyl-3-methylimidazolium bromide (BmimBr) were chemically immobilized in NH₂-MIL-101 nanocages. The amine of DMEDA was grafted onto carrier NH₂-MIL-101 by N–Cr coordinate covalent bonds and the ionic liquid of BmimBr (IL (Br⁻)) was anchored in the NH₂-MIL-101 nanocages by ‘ship-in-a-bottle’ method, in which the amidogen of NH₂-MIL-101 condensed with N, N-carbonyldiimidazole (CDI) firstly, and then alkylated with 1-bromo butane. This novel heterogeneous catalyst with two different active sites can efficiently catalyze the synthesis of N-aryl oxazolidin-2-ones from carbon dioxide (CO₂), epoxides, and anilines in one-pot under mild solvent-free conditions. It not only showed good stability and recoverability after five cycles but also exhibited shape selectivity for the substrate due to the synergic catalysis of amine, ionic liquid, and NH₂-MIL-101. This novel bifunctional material is a promising solid catalyst for the green synthesis of N-aryl oxazolidin-2-ones.

Hexagonal boron nitride: A metal-free catalyst for deep oxidative desulfurization of fuel oils

Peiwen Wu, Linjie Lu, Jing He, Linlin Chen, Yanhong Chao, Minqiang He, Fengxia Zhu, Xiaozhong Chu, Huaming Li, Wenshuai Zhu

2020, 5(2): 166-172. doi: 10.1016/j.gee.2020.03.004

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Oxidative desulfurization (ODS) has been proved to be an efficient strategy for the production of clean fuel oil. Numerous metal-based materials have been employed as excellent ODS catalysts, but being hindered by their high-cost and potential secondary pollution. In this work, we employed graphene analogous hexagonal boron nitride (h-BN) as a metal-free catalyst for ODS with hydrogen peroxide (H₂O₂) as the oxidant. The h-BN catalyst was characterized and proved to be a few-layered structure with relatively high specific surface areas. The h-BN catalyst showed a 99.4% of sulfur removal in fuel oil under the optimized reaction conditions. Besides, the h-BN can be recycled for 8 times without significant decrease in the catalytic performance. Detailed mechanism analysis found that it is the boron radicals in h-BN activated H₂O₂ to generate ·OH species, which can readily oxidize sulfides to corresponding sulfones for separation. This work would provide another choice in choosing metal-free catalysts for ODS.

Extractive denitrogenation of shale oil using imidazolium ionic liquids

Shurong Gao, Shengfan Fang, Ruozheng Song, Xiaochun Chen, Guangren Yu

2020, 5(2): 173-182. doi: 10.1016/j.gee.2020.04.002

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The potential applications of shale oil as a substitute energy source are adversely influenced due to its high nitrogen content. In this work, four imidazolium ionic liquids (ILs), i.e., 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-butyl-3-methylimidazolium acetate ([Bmim]Ac), 1-butyl-3-methylimidazolium acetate/ZnAc₂ ([Bmim]Ac/ZnAc₂) and 1-butyl-3-methylimidazolium chloride/ZnAc₂ ([Bmim]Cl/ZnAc₂), were used to extract the basic nitrides and neutral nitrides from shale oil. The influence of extraction time, temperature, properties of N-compounds, ILs structure, mass ratio of IL/oil, multiple cycles of denitrogenation, physical mixing of ILs and ILs recyclability on extractive denitrogenation was systematically investigated. The denitrogenation performance of all ILs was determined and investigated from micro-level view withσ-profile. It was observed that, ILs composed of anions with weaker HB acceptor capacity, have the higher N-extraction efficiency to the neutral nitrogen compounds with weaker HB acceptor capacity. More than 96% N-extraction efficiency was achieved at the end of a single extraction cycle for time < 10 min under 40 °C and 1 : 1 of IL: oil (w/w), especially 100% N-extraction efficiency was realized for carbazole and indole. The N-extraction efficiency up to 60.1% and 53.7% for real shale oil was realized by [Bmim]Ac and [Bmim]Ac/ZnAc ₂, respectively, which are about 10% better than other non-hydrodenitrogenation technologies. Moreover, [Bmim]Ac and [Bmim]Ac/ZnAc₂ exhibited almost the same extractive denitrogenation performance after regeneration. This work has developed a new approach to lessen the nitrogen content of shale oil effectively and economically.

Protic vs aprotic ionic liquid for CO₂ fixation: A simulation study

Wenzhong Sun, Meichen Wang, Yaqin Zhang, Weilu Ding, Feng Huo, Li Wei, Hongyan He

2020, 5(2): 183-194. doi: 10.1016/j.gee.2020.04.004

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The cycloaddition of CO₂ with epoxides catalyzed by ionic liquids (ILs) has been a widely ongoing studied hot topic over the years. Recent experimental research has shown that the protic ionic liquids (PILs) behave stronger hydrogen proton donating ability than aprotic ionic liquids (APILs), and can effectively catalyze the cycloaddition of CO₂. Unfortunately, the mechanistic explanation remains primarily unraveled. Herein, a detailed simulation study on the cycloaddition reaction catalyzed by PIL ([HDBU][Mim]) in comparison with APIL ([MeDBU][Mim]) reaction catalysts was conducted, including the three-step route (ring-opening of PO (propylene oxide), insertion of CO₂ and ring-closure of propylene carbonate (PC)) and two-step route (simultaneously ring-opening of PO and addition of CO₂, and then ring-closure of PC). Based on the activation energy barrier of the rate-determining step, PIL preferentially activates PO as the optimal route for the reaction with the energy barrier of 23.2 kcal mol^-1, while that of APIL is 31.2 kcal mol^-1. The role of [HDBU]⁺ in the reaction was also explored and found that the direct formation of intermolecular hydrogen bond (H-bond) between [HDBU]⁺ and the reactants (PO + CO₂) was unfavorable for the reaction, while the cooperation with the anion [Mim]^- to assist indirectly was more conducive. To fully consider the reaction microenvironment of ILs, ONIOM calculation was used to study the solvent effect. At last, the above conclusions were further verified by the analysis of intermediates with charge, non-covalent interaction (NCI), and atoms in molecules (AIM) methods. The computational findings show that ILs studied in this work have dual functions of catalyst and solvent, enabling a microscopic understanding of the ILs catalyst for CO₂ utilization as well as providing guidance for the rational design of more efficient ILs-based catalysts.

Design of functionalized fluorescent ionic liquid and its application for achieving significant improvements in Al³⁺ detecting

Lu Gan, Jiachen Guo, Siying Che, Qiaoxin Xiao, Mingyang Wang, Jienan You, Congmin Wang

2020, 5(2): 195-202. doi: 10.1016/j.gee.2020.03.006

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Specific fluorophore was introduced into ionic liquid based on its tunability, thus a kind of novel fluorescent ionic liquid probe [P₆₆₆₁₄][HQS] was designed, synthesized and characterized. Compared with non-fluorescent HQS, ionic liquid [P₆₆₆₁₄][HQS] emitted a certain amount of fluorescence, which could be attributed to the well-delocalized frontier orbitals and its charge transfer character, as demonstrated by quantum chemical calculation. Considering the interaction of [P₆₆₆₁₄][HQS] with metal ions, the application for detecting specific substance as a chemical sensor, such as Al³⁺ was investigated. Compared with the traditional probe HQS, significant improvements in Al³⁺ detecting was achieved by [P₆₆₆₁₄][HQS] with stronger binding ability, better sensitivity and selectivity. The better performance of [P₆₆₆₁₄][HQS] was contributed to the changed charge distribution, leading to the stronger binding interaction. We believe that this new fluorescent ionic liquid exhibited unique properties in detecting Al³⁺ in aqueous solution, which would broaden the application of ionic liquids.

Construction of NH₂-MIL-125(Ti)/Bi₂WO₆ composites with accelerated charge separation for degradation of organic contaminants under visible light irradiation

Sheng Yin, Yong Chen, Ming Li, Qingsong Hu, Yi Ding, Yifan Shao, Jun Di, Jiexiang Xia, Huaming Li

2020, 5(2): 203-213. doi: 10.1016/j.gee.2020.03.008

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Photocatalysis is considered as an ideal strategy for water pollution treatment. However, it remains challenging to design a highly efficient photocatalytic system through regulating the charge flow via a precise approach. In this work, a novel NH₂-MIL-125(Ti)/Bi₂WO₆ composite was constructed via self-assembly growing Bi₂WO₆ nanosheets on NH₂-MIL-125(Ti) material. The characterization results demonstrated that NH₂-MIL-125(Ti) was successfully incorporated into Bi₂WO₆ and the photoexcited carriers could be efficiently separated and transferred between the two components. NH₂-MIL-125(Ti)/Bi₂WO₆ composites displayed enhanced photocatalytic activity for the removal of rhodamine B (RhB) and tetracycline (TC) under visible light irradiation, and the optimal weight ratio of NH₂-MIL-125(Ti) was determined to be 7 wt%. The introduction of NH₂-MIL-125(Ti) into Bi₂WO₆ could raise the absorption of visible light, accelerate the separation and transfer of charge carriers, and boost photocatalytic activity. This research presents a wide range of possibilities for the further development of novel composites in the field of environment purification.

Corrosion inhibiting performance and mechanism of protic ionic liquids as green brass inhibitors in nitric acid

Pengcheng Hu, Zhitao Wu, Junlin Wang, Yuqing Huang, Quanyou Liu, Shu-Feng Zhou

2020, 5(2): 214-222. doi: 10.1016/j.gee.2019.11.003

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Four protic ionic liquids (ILs) were synthesized via a one-step method by using benzotriazole (BTA) and benzimidazole as cations, and benzenesulfonic acid and 2-naphthalenesulfonic acid (NSA) as anions. These ILs were used as green corrosion inhibitors for brass specimens in a nitric acid solution. The structure of the protic ILs was characterized by ¹H-NMR, ¹³C-NMR, and FT-IR spectroscopy. The effects of the IL structure, IL concentration, acid concentration, and corrosion time on the surface morphology of brass specimens and the inhibition efficiency (η%) of ILs were investigated by the weight loss method combined with SEM and EDS spectroscopy. Polarization curves and impedance spectroscopy were used to analyze the electrochemical corrosion inhibition mechanism of ILs. Results showed that IL synthesis was a proton transfer process, and the proton of the –SO₃H group on NSA was deprived by BTA. IL [BTA][NSA], which had a high charge density and large conjugate π band, was the most effective inhibitor for brass corrosion. Theη% of [BTA][NSA] decreased with the increase in acid concentration and corrosion time, which showed an increment with the increase in [BTA][NSA] concentration. The higher theη% of [BTA][NSA] is, the smoother the surface of the brass specimens is, and the smaller the undistributed area of Cu element will be. Corrosion inhibiting mechanism from electrochemical analysis indicated that the addition of [BTA][NSA] increased the polarization resistance of the brass electrode significantly and suppressed both anodic and cathodic reactions.

A facile ionic liquid approach to prepare cellulose fiber with good mechanical properties directly from corn stalks

Jiming Yang, Xingmei Lu, Yanqiang Zhang, Junli Xu, Yongqing Yang, Qing Zhou

2020, 5(2): 223-231. doi: 10.1016/j.gee.2019.12.004

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It is very difficult to directly spin the lignocellulose without pretreatment. Ionic liquids (ILs) are promising solvent to dissolve lignocellulose to prepare cellulose fiber. However, the degree of cellulose polymerization（DP）is reduced when lignocellulose is dissolved in ILs, and the lignin removal rate is low. The elongation at break and tensile strength of the fibers obtained by spinning the lignocellulose dissolved in ILs are poor. In this paper, preparing cellulose fiber directly from lignocellulose based on dissolving corn stalk via [C ₄mim]Cl-L-arginine binary system is achieved. It shows that the removal rate of lignin can reach 92.35% and the purity of cellulose can reach 85.32% after corn stalk was dissolved at 150 °C for 11.5 h when the mass fraction of arginine is 2.5%. The elongation at break of fiber reached 10.12% and the tensile strength reached 420 MPa. It is mainly due to the fact that L-arginine not only inhibits the degradation of cellulose but also promotes the delignination. Without any pulping or pretreatment, preparing cellulose fibers via direct dissolution and extrusion may provide a simple and effective way to prepare many novel cellulose materials.

Dissolution of highly molecular weight cellulose isolated from wheat straw in deep eutectic solvent of Choline/l-Lysine hydrochloride

Jiake Wang, Yan Wang, Zhongzheng Ma, Lifeng Yan

2020, 5(2): 232-239. doi: 10.1016/j.gee.2020.03.010

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Green solvents for cellulose dissolution is a key topic for green chemistry, especially natural cellulose with high molecular weight, and there are scarce solvents reported. Deep eutectic solvent (DES) is a typical kind of green solvent that has been attracted much attention recently. Here, high molecular weight natural cellulose (DP > 3000) was first isolated from wheat straw and then be directly dissolved in the choline/l-lysine (Ch/Lys) DES. The solution owns excellent stability, and the solubility reaches ∼5%. Rheological studies revealed that the natural cellulose can be well dispersed in the DES solution and showed gelation at high concentrations. The dissolved cellulose can be regenerated when the dilute acid aqueous solution was added into the solution. It provides an energy conversation and an environmentally friendly route to prepare a cellulose solution, which makes it possible to convert cellulose to valuable chemicals and materials in its homogeneous solution.

Getting closer to the outstanding scientist in the field of ionic liquid—An interview with Prof. Robin D. Rogers

Jing Kong, Hongyan He

2020, 5(2): 240-242. doi: 10.1016/j.gee.2020.06.001

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Challenge and opportunity of ionic liquids—An interview with Prof. Douglas R. Macfarlane

Jing Kong, Hongyan He

2020, 5(2): 243-245. doi: 10.1016/j.gee.2020.06.002

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2020 Vol. 5, No. 2

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