离子液体限域于硅胶纳米孔道中的电化学行为研究(英文)

通过溶胶-凝胶法制备了硅胶包载咪唑类离子液体修饰电极,研究其与体相离子液体不同的伏安行为;另一方面,制备不同离子液体含量为15% ~ 28%的包载离子液体硅胶和涂覆离子液体硅胶,用电化学阻抗研究其在20 ^oC到80 ^oC下电导率的变化情况. 异常的电化学行为主要表现在：1)硅胶包载离子液体导致Fc/Fc⁺电对的半波电位正移63.5 ~ 200 mV;2)当离子液体限域于硅胶纳米孔道中时,离子液体的电化学稳定性变差;3)包载离子液体硅胶的电导率要比涂覆离子液体的电导率高29.6% ~ 136%. 由此推断,可能是由于离子液体充满硅胶孔腔和孔道从而形成了纳米网状的离子液体导电介质. 这些结果表明,硅胶包载离子液体不仅可以作为修饰电极的优良载体,而且也有助于理解离子液体限域于硅胶纳米孔道中的限域效应.     

Transforming Porous Organic Cages into Porous Ionic Liquids via a Supramolecular Complexation Strategy

Porous liquids are a type of porous materials that engineer permanent porosity into unique flowing liquids, exhibiting promising functionalities for a variety of applications. Here a Type I porous liquid is synthesized by transforming porous organic cages into porous ionic liquids via a supramolecular complexation strategy. Simple physical mixing of 18‐crown‐6 with task‐specific anionic porous organic cages affords a porous ionic liquid with anionic porous organic cages as the anionic parts and 18‐crown‐6/potassium ion complexes as the cationic parts. In contrast, mixing of 15‐crown‐5 and anionic porous organic cages in a 2:1 ratio gives only solids, while the addition of excess 15‐crown‐5 affords a Type II porous liquid. The permanent porosity in the cage‐based porous liquids has been also confirmed by molecular simulation, positron (e⁺) annihilation lifetime spectroscopy, and enhanced gas sorption capacity compared with pure crown ethers.     

离子液体在多孔碳电极上的电化学性能

制备了数种离子液体及离子液体有机溶液电解质,用线性电位扫描法测试了它们的电化学窗口;并通过循环伏安、交流阻抗、电势阶跃等电化学方法,对它们在多孔碳电极中的电化学性能进行了研究.实验结果表明:溶剂对1-乙基-3-甲基咪唑类离子液体有机溶液电解质的电化学窗口有较大的影响.离子液体及离子液体有机溶液电解质在多孔碳电极上的电化学性能与其电导率密切相关,电导率越大,充电时间常数越小,比容量越大;但比容量降低的倍率远小于电导率降低的倍率.     

功能离子液体/氧化硅基多孔复合材料*

利用有巨大界面特征和发达孔道结构的氧化硅基多孔材料作为功能离子液体的载体,不仅可实现离子液体的固相化从而解决均相离子液体分离难的瓶颈,而且也可增加离子液体的比表面积进而提高离子液体的使用效率和稳定性;探索结合离子液体和氧化硅基多孔材料双重优点的目标功能材料的制备及应用成为近年来的一个研究热点。本文综述了离子液体/氧化硅基多孔复合材料的最新研究进展,探讨了其合成手段的有效性,并对其应用前景进行了展望。     

Complementing Crystallography with Ultralow‐Frequency Raman Spectroscopy: Structural Insights into Nitrile‐Functionalized Ionic Liquids

Functionalized ionic liquids are a subclass of ionic liquids that are tailored for a specific application. Structural characterization in both solid and liquid phases is central to understanding their physical properties. Here, we used ultralow‐frequency Raman spectroscopy, which can measure Raman spectra down to approximately 5 cm^?1, to study the structures and physical properties of 1‐(4‐cyanobenzyl)‐3‐methylimidazolium salts with five different anions. A comparison of the observed low‐frequency Raman spectral patterns enabled us to predict the crystal symmetry of one of the synthesized salts for which single‐crystal X‐ray diffraction data were unobtainable. Real‐time tracking of the low‐frequency Raman spectral changes during melting revealed peak shifts indicative of different degrees of microscopic heterogeneity in the ionic liquids. The results show that our method provides a facile means that is complementary to X‐ray crystallography, for obtaining structural information of ionic liquids.     

Confinement Effects on the Magnetic Ionic Liquid 1-Ethyl-3-methylimidazolium Tetrachloroferrate(III)

Confinement effects for the magnetoresponsive ionic liquid 1-ethyl-3-methylimidazolium tetrachloroferrate(III), [C₂mim]FeCl₄, are explored from thermal, spectroscopic, and magnetic points of view. Placing the ionic liquid inside SBA-15 mesoporous silica produces a significant impact on the material’s response to temperature, pressure, and magnetic fields. Isobaric thermal experiments show melting point reductions that depend on the pore diameter of the mesopores. The confinement-induced reductions in phase transition temperature follow the Gibbs–Thomson equation if a 1.60 nm non-freezable interfacial layer is postulated to exist along the pore wall. Isothermal pressure-dependent infrared spectroscopy reveals a similar modification to phase transition pressures, with the confined ionic liquid requiring higher pressures to trigger phase transformation than the unconfined system. Confinement also impedes ion transport as activation energies are elevated when the ionic liquid is placed inside the mesopores. Finally, the antiferromagnetic ordering that characterizes unconfined [C₂mim]FeCl₄ is suppressed when the ionic liquid is confined in 5.39-nm pores. Thus, confinement provides another avenue for manipulating the magnetic properties of this compound.     

Water-Induced Breaking of the Coulombic Ordering in a Room-Temperature Ionic Liquid Metal Complex

Control of ion arrangements in ionic liquids represents a major challenge owing to the presence of the predominant coulombic interactions between cationic and anionic ion species that forms the coulombic ordering. Here, water-induced ion rearrangement in a room-temperature ionic liquid (RT-IL) metal complex, (1-ethyl-3-methylimidazolium)₂[MnN(CN)₄], is demonstrated through coordinative interactions between anions. Solidification occurred, which was associated with the formation of a “separated” structure consisting of cation columns and anionic cyanide-bridged one-dimensional coordination polymers. The energy diagram is in accord with the resultant RT-IL incorporating mononuclear [MnN(CN)₄]²⁻ molecules being a kinetic phase stabilized by inter-ion repulsions of the anionic divalent metal complex moieties. Water acts to decrease the coulombic interactions, including repulsion, giving rise to breaking of the coulombic ordering arising from coordination bond formation in the IL phase.     

The Effect of Fluorinated Solvents on the Physicochemical Properties,Ionic Association,and Free Volume of a Prototypical Solvate Ionic Liquid

Solvate ionic liquid (SIL) synthesis and properties depend on a delicate balancing of cation-solvent and cation-anion interactions to produce materials containing only cation-solvent complexes and solvent-separated anions. Most SILs meeting these characteristics fall within the paradigm of oligomeric ethylene oxides (e.g. glymes and glycols) and lithium salts. Targeted functionalization of solvent molecules to achieve desired properties is a relatively unexplored avenue of research. Fluorinated solvents have significantly different electric charge distributions compared to their nonfluorinated analogs. We test the impact of solvent fluorination for a SIL created from equimolar mixtures of lithium bis(trifluoromethylsulfonyl)imide (LiNTf₂) and triethylene glycol (TEG), hereafter [(TEG)₁Li]NTf₂. In the first experiment, TEG is partially substituted with 2,2,4,4,5,5,7,7-octafluoro-3,6-dioxaoctane-1,8-diol (FTEG). This leads to a precipitous decrease in ionic conductivity and larger quantities of ionically-associated Li(NTf₂)₂⁻ species, as detected with vibrational spectroscopy. These observations suggest FTEG does not readily coordinate Li⁺ ions in a manner analogous to TEG. Computational studies reinforce this conclusion. Relative complex cation stabilities are ranked as [(FTEG)₁Li]⁺>[(TEG)₁Li]⁺. A second experiment adds FTEG as a diluent to [(TEG)₁Li]NTf₂. This places FTEG and TEG in competition to coordinate a limited number of Li⁺ ions. The resulting mixtures exhibit conductivity enhancement over the parent SIL and minimal changes in ion speciation due to the poor Li⁺ binding by FTEG compared to TEG. Positron annihilation lifetime spectroscopic studies point to increased amounts of free volume upon dilution of FTEG. This likely explains the origin of the conductivity and viscosity enhancements.     

Azolate Anions in Ionic Liquids: Promising and Under-Utilized Components of the Ionic Liquid Toolbox

Owing to their ease of synthesis, diffuse positive charge, and chemical stability, 1-alkyl-3-methylimidazolium cations (i.e., [C_nmim]⁺) are one of the most routinely utilized and historically important components in ionic liquid (IL) chemistry. However, while this is a routinely encountered member of the IL family as cations, relatively few workers have explored the versatile chemistry of azoles to allow their use as an anionic component in ILs, as azolates. Azolate anions possess many of the desired properties for IL formation, including a diffuse ionic charge, tailorable asymmetry, and synthetic flexibility, with the added advantages of not relying on halogen atoms for electron-withdrawing effects, as is commonly encountered with IL anions such as hexafluorophosphate. This review explores the 122 azolate-containing ILs known in the literature (prepared from only 39 disparate azolate anions), with a view to highlighting not only their demonstrated utility as an IL component, but the ways in which the larger scientific community may utilize their advantageous properties for new tailored materials.     

Phase Transitions and Electrochemical Properties of Ionic Liquids and Ionic Liquid—Solvent Mixtures

Recent advances in studies of ionic liquids (IL) and ionic liquid–solvent mixtures are reviewed. Selected experimental, simulation, and theoretical results for electrochemical, thermodynamical, and structural properties of IL and IL-solvent mixtures are described. Special attention is paid to phenomena that are not predicted by the classical theories of the electrical double layer or disagree strongly with these theories. We focus on structural properties, especially on distribution of ions near electrodes, on electrical double layer capacitance, on effects of confinement, including decay length of a dissjoining pressure between confinig plates, and on demixing phase transition. In particular, effects of the demixing phase transition on electrochemical properties of ionic liquid–solvent mixtures for different degrees of confinement are presented.     

Ligand Effect on Physicochemical Properties of Ionic Liquid

In the solvent extraction process, the importance of an extractant (or ligand) and a diluent is inferred from their respective physicochemical properties. We have brought together all the recent results reported on the mixture of different extractants dissolved in a well-known ionic liquid diluent: 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C₄mim][NTf₂]) in the form of a review and aimed to emphasize the role of ligand polarity and structure on the physicochemical properties of an ionic liquid (IL) diluent. Some of the most important properties such as dynamic viscosity (η), absolute density ( ), energy of activation (E_a), coefficient of thermal expansion (α), phase separation time (PST), refractive index (n), etc., have been discussed meticulously in the paper. The effect of ligand structure on the aggregation behaviour of IL phase and the physicochemical properties of gamma irradiated solvent phases containing different ligands and their solution with IL phase also have been deliberated in detail.     

多孔离子液体的构筑及应用

多孔液体(Porous Liquids, PLs)是一类结合了多孔固体永久性孔隙与液态流动性优势的新材料. 自2007年, PLs的概念被首次提出以来, 其在合成策略与应用领域方面均取得了较大的突破. 然而, 传统的PLs因高黏度、高密度、高熔点与高原材料成本等缺陷极大程度制约了其在流动工业系统中的大规模应用. 因此, 迫切需要寻求理想的位阻溶剂用于制备先进的多孔液体. 离子液体(Ionic Liquids, ILs)因独特的可调节物理特性、非挥发性、高稳定性、易获得、经济性高、低再生能耗等特性, 使其成为构筑PLs中最具有应用前景的理想溶剂之一. 在过去的5年间, 基于多种ILs与先进多孔固体(如有机笼、金属有机框架、中空碳、沸石、多孔聚合物等)制备的多孔离子液体(Porous Ionic Liquids, PILs)被陆续报道. PILs独特的永久性孔隙、无溶剂挥发、再生能力强、黏度可调、低熔点、高稳定性等特性加快了其在气体吸附、分离、催化、萃取、分子分离等领域的快速发展. 本综述围绕PILs的构筑策略、特性、应用领域等阐述了其研究进展. 最后, 对PILs在制备中存在的挑战与未来的研究方向进行了归纳与展望.     

新型室温离子液体六烷基胍盐的制备及性质

近年来 ,离子液体 (IL)作为“绿色”溶剂受到学术和工业界的关注 .英国 BP公司和法国的 IFP等研究机构从 2 0世纪 80年代起就开始探索离子液体作为溶剂与催化剂的可能性 ,至今在离子液体体系中已实现了许多催化反应 [1～ 5] .室温离子液体 (RTIL S)是指在常温下呈液态的熔盐体系 .通常由烷基吡啶或双烷基咪唑季铵阳离子与氯铝酸根、氟硼酸根及氟磷酸根等阴离子组成 .在季铵盐类离子液体中 ,咪唑盐的合成和应用研究尤为突出 .目前 ,对于既可作为溶剂又可作为催化剂的室温离子液体的合成和应用已成为研究热点 [6 ] ,如室温离子液体 [EMI…     

新型磺酸功能化离子液体理化性质的研究

合成了三类磺酸功能化离子液体,通过STA、DSC-TG、UV-Vis、运动粘度/密度计等手段考察了离子液体的热力学性质、酸度、粘度和密度等理化性质,发现离子液体阴阳离子的结构对这些理化性质有不同程度的影响,并对离子液体的结构与理化性质变化关系进行初步探讨.     

Introduction of an Ionic Liquid into the Micropores of a Metal–Organic Framework and Its Anomalous Phase Behavior

Controlling the dynamics of ionic liquids (ILs) is a significant issue for widespread use. Metal–organic frameworks (MOFs) are ideal host materials for ILs because of their small micropores and tunable host–guest interactions. Herein, we demonstrate the first example of an IL incorporated within the micropores of a MOF. The system studied consisted of EMI‐TFSA (1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)amide) and ZIF‐8 (composed of Zn(MeIM)₂; H(MeIM)=2‐methylimidazole) as the IL and MOF, respectively. Construction of the EMI‐TFSA in ZIF‐8 was confirmed by X‐ray powder diffraction, nitrogen gas adsorption, and infrared absorption spectroscopy. Differential scanning calorimetry and solid‐state NMR measurements showed that the EMI‐TFSA inside the micropores demonstrated no freezing transition down to 123 K, whereas bulk EMI‐TFSA froze at 231 K. Such anomalous phase behavior originates from the nanosize effect of the MOF on the IL. This result provides a novel strategy for stabilizing the liquid phase of the ILs down to a lower temperature region.     

Determination of Solubility Parameters of Ionic Liquids and Ionic Liquid/Solvent Mixtures from Intrinsic Viscosity

The total and partial solubility parameters (dispersion, polar and hydrogen‐bonding solubility parameters) of ten ionic liquids were determined. Intrinsic viscosity approaches were used that encompassed a one‐dimensional method (1D‐Method), and two different three‐dimensional methods (3D‐Method1 and 3D‐Method2). The effect of solvent type, the dimethylacetamide (DMA) fraction in the ionic liquid, and dissolution temperature on solubility parameters were also investigated. For all types of effect, both the 1D‐Method and 3D‐Method2 present the same trend in the total solubility parameter. The partial solubility parameters are influenced by the cation and anion of the ionic liquid. Considering the effect on partial solubility parameters of the solvent type in the ionic liquid, it was observed that in both 3D methods, the dispersion and polar parameters of a 1‐ethyl‐3‐methylimidazolium acetate/solvent (60:40 vol %) mixture tend to increase as the total solubility parameter of the solvent increases.     

离子液体中制备无机材料

离子液体作为潜在的“绿色”溶剂,具有许多传统溶剂无法比拟的优异性能,在有机合成、催化、液液分离和萃取等领域引起了广泛的研究。而在离子液体领域无机材料的制备是一个较新的发展分支,现已利用其合成出多种具有独特结构和性能的无机材料。本文就离子液体在无机材料制备方面的应用及发展趋势进行了综述。目前,对于制备无机材料,离子液体主要是作为电解液、表面活性剂或溶剂,本文介绍了其在应用中的优缺点,并指出该领域未来的发展趋势是离子热合成和集模板-溶剂-反应物于一身的离子液体反应。