A Fully Integrated Continuous‐Flow System for Asymmetric Catalysis: Enantioselective Hydrogenation with Supported Ionic Liquid Phase Catalysts Using Supercritical CO2 as the Mobile Phase

A continuous‐flow process based on a chiral transition‐metal complex in a supported ionic liquid phase (SILP) with supercritical carbon dioxide (scCO₂) as the mobile phase is presented for asymmetric catalytic transformations of low‐volatility organic substrates at mild reaction temperatures. Enantioselectivity of >99 % ee and quantitative conversion were achieved in the hydrogenation of dimethylitaconate for up to 30 h, reaching turnover numbers beyond 100 000 for the chiral QUINAPHOS–rhodium complex. By using an automated high‐pressure continuous‐flow setup, the product was isolated in analytically pure form without the use of any organic co‐solvent and with no detectable catalyst leaching. Phase‐behaviour studies and high‐pressure NMR spectroscopy assisted the localisation of optimum process parameters by quantification of substrate partitioning between the IL and scCO₂. Fundamental insight into the molecular interactions of the metal complex, ionic liquid and the surface of the support in working SILP catalyst materials was gained by means of systematic variations, spectroscopic studies and labelling experiments. In concert, the obtained results provided a rationale for avoiding progressive long‐term deactivation. The optimised system reached stable selectivities and productivities that correspond to 0.7 kg L ^?1 h^?1 space–time yield and at least 100 kg product per gram of rhodium, thus making such processes attractive for larger‐scale application.     

The Co‐Entrapment of a Homogeneous Catalyst and an Ionic Liquid by a Sol–gel Method: Recyclable Ionogel Hydrogenation Catalysts

Molecular hydrogenation catalysts have been co‐entrapped with the ionic liquid [Bmim]NTf₂ inside a silica matrix by a sol–gel method. These catalytic ionogels have been compared to simple catalyst‐doped glasses, the parent homogeneous catalysts, commercial heterogeneous catalysts, and Rh‐doped mesoporous silica. The most active ionogel has been characterised by transmission electron microscopy, X‐ray photoelectron spectroscopy, and solid state NMR before and after catalysis. The ionogel catalysts were found to be remarkably active, recyclable and resistant to chemical change.     

High Performance Fe Porphyrin/Ionic Liquid Co‐catalyst for Electrochemical CO2 Reduction

The efficient and selective catalytic reduction of CO₂ is a highly promising process for both of the storage of renewable energy as well as the production of valuable chemical feedstocks. In this work, we show that the addition of an ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate, in an aprotic electrolyte containing a proton source and FeTPP, promotes the in situ formation of the [Fe⁰TPP]^2? homogeneous catalyst at a less negative potential, resulting in lower overpotentials for the CO₂ reduction (670 mV) and increased kinetics of electron transfer. This co‐catalysis exhibits high Faradaic efficiency for CO production (93 %) and turnover number (2 740 000 after 4 hour electrolysis), with a four‐fold increase in turnover frequency (TOF) when compared with the standard system without the ionic liquid.     

聚吡咯薄膜在超临界CO_2与离子液体两相体系中的电化学合成

首次在超临界CO2与离子液体两相体系中实现了聚吡咯（PPyr）薄膜的电化学合成.与纯离子液体相比,该体系中合成的PPyr膜具有均匀平滑的表面.随着CO2压力的增加,膜的生长速度减慢,膜的表面变得更加均匀平滑.     

Computer‐Aided Design of Ionic Liquids as CO2 Absorbents

Ionic liquids (ILs), vary strongly in their interaction with CO₂. We suggest simple theoretical approach to predict the CO₂ absorption behavior of ILs. Strong interaction of the CO₂ with the IL anions corresponds to chemical absorption whereas weak interaction indicates physical absorption. A predictive estimate with a clear distinction between physical and chemical absorption can be simply obtained according to geometries optimized in the presence of a solvation model instead of optimizing it only in gas phase as has been done to date. The resulting Gibbs free energies compare very well with experimental values and the energies were correlated with experimental capacities. Promising anions, for ionic liquids with reversible CO₂ absorption properties can be defined by a reaction Gibbs free energy of absorption in the range of ?30 to 16 kJ mol^?1.     

Extraction of Uranium from Aqueous Solutions by Using Ionic Liquid and Supercritical Carbon Dioxide in Conjunction

Super powers! Uranium(VI) ions can be extracted from aqueous solutions into supercritical CO₂ (sc‐CO₂) via an ionic liquid phase that contained tri‐n‐butyl phosphate (TBP) as a complexing agent (see figure). This process has potential applications in the nuclear industry for removing actinides from nuclear waste.

     

Homogeneous Light‐Driven Catalytic Direct Carboxylation with CO2

Carbon dioxide is a ubiquitous and inexpensive one‐carbon source for chemical synthesis, and the efficient incorporation of CO₂ into organic molecules is of widespread research interest both for economic and ecological reasons. The methodologies to employ carbon dioxide as a single‐carbon unit to construct molecules relevant for agrochemical and pharmaceutical research include many elegant approaches, including asymmetric transformations. Even though remarkable achievements have been made in the field of light‐driven catalysis, especially photoredox catalysis, homogeneous light‐driven catalytic carboxylation by employing CO₂ as the key reagent has only become a subject of increasing attention in recent years. Therefore, this concise review will discuss the latest advances in this research area.     

Study on the phase behaviors,viscosities, and thermodynamic properties of CO2/[C(4)mim][PF(6)]/methanol system at elevated pressures

An apparatus to determine the vapor-liquid equilibria of CO(2)/ionic liquid (IL)/organic solvent multisystems and the viscosity of the liquid phase at elevated pressures has been constructed. The solubility of CO(2) in 3-butyl-1-methyl-imidazolium hexafluorophosphate ([C(4)mim][PF(6)]) and the viscosity of CO(2)-saturated [C(4)mim][PF(6)] have been studied at 313.15, 323.15, and 333.15 K and at pressures up to 12.5 MPa. The phase behavior of CO(2)/[C(4)mim][PF(6)]/methanol ternary mixture and the viscosity of the liquid phases at equilibrium condition have also been determined at 313.15 K and at 7.15 and 10.00 MPa. The partition coefficients of the components in the ternary system are calculated. Peng-Robinson equation of state and some thermodynamic functions are combined to calculate the fugacity coefficients of the components in the system. It demonstrates that the viscosity of the IL-rich phase decreases significantly with increasing pressure of CO(2), and the effect of temperature on the viscosity of CO(2)/IL mixture is not noticeable at high pressure, although the viscosity of the CO(2)-free IL decreases dramatically with increasing temperature. Compressed CO(2) may become an attractive reagent for reducing the viscosity of ILs in many applications. The mole fraction of methanol in the CO(2)-rich phase is much lower than that in the IL-rich phase; this indicates that the interaction between the IL and methanol is stronger than that between CO(2) and methanol. The fugacity coefficient of CO(2) in IL-rich phase is larger than unity, while that of methanol is much small than unity, which further suggests that methanol-IL interaction is much stronger than CO(2)-IL interaction. However, the CO(2)-IL interaction is stronger than the CO(2)-methanol interaction.     

Immobilization of Ionic Liquid on a Covalent Organic Framework for Effectively Catalyzing Cycloaddition of CO2 to Epoxides

Transforming CO₂ into value-added chemicals has been an important subject in recent years. The development of a novel heterogeneous catalyst for highly effective CO₂ conversion still remains a great challenge. As an emerging class of porous organic polymers, covalent organic frameworks (COFs) have exhibited superior potential as catalysts for various chemical reactions, due to their unique structure and properties. In this study, a layered two-dimensional (2D) COF, IM4F-Py-COF, was prepared through a three-component condensation reaction. Benzimidazole moiety, as an ionic liquid precursor, was integrated onto the skeleton of the COF using a benzimidazole-containing building unit. Ionization of the benzimidazole framework was then achieved through quaternization with 1-bromobutane to produce an ionic liquid-immobilized COF, i.e., BMIM4F-Py-COF. The resulting ionic COF shows excellent catalytic activity in promoting the chemical fixation of CO₂ via reaction with epoxides under solvent-free and co-catalyst-free conditions. High porosity, the one-dimensional (1D) open-channel structure of the COF and the high catalytic activity of ionic liquid may contribute to the excellent catalytic performance. Moreover, the COF catalyst could be reused at least five times without significant loss of its catalytic activity.     

Infrared Spectroscopy of a Wilkinson Catalyst in a Room‐Temperature Ionic Liquid

Homogeneous catalysis in room‐temperature ionic liquids (ILs) constitutes a most interesting field of research with high potential in technical applications. As concerns the hydrogenation of unsaturated hydrocarbons, Wilkinson’s compound RhCl(PPh₃)₃ represents a catalyst that provides high selectivity and activity. Herein, we demonstrate the application of infrared spectroscopy to the quantitative analysis of the Wilkinson catalyst in the IL 1‐ethyl‐3‐methylimidazolium acetate ([EMIM][OAc]). Our study demonstrates for the first time the quantitative, accurate and reproducible determination of the concentration of a rhodium catalyst by means of IR spectroscopy and, moreover, allows the investigation of intermolecular interactions. Spectral features, located mainly in the fingerprint region of the IR spectrum, are identified revealing the influence of the dissolved catalyst on the IL’s vibrational structure. In particular, the ring‐bending mode of the imidazolium ring shows a frequency shift as a function of catalyst concentration, probably due to hydrogen‐bond formation between the IL cation and the Rh complex. The results show the potential of IR spectroscopy both for application as a quick process control technology in catalytic processes and as a tool for better understanding of IL–catalyst interactions.     

Dual Amino‐Functionalised Phosphonium Ionic Liquids for CO2 Capture

CO ₂ is locked up : Dual amino‐functionalised phosphonium ionic liquids (ILs; see figure) have been prepared. The ILs have excellent thermal properties, such as low glass transition temperatures and high thermal decomposition temperatures. The supported CO₂ absorption of four of the ILs on porous SiO₂ was found to approach one mol CO₂ per mol IL, a factor of two greater than that reported before.

     

Recent Advances in Homogeneous Carbonylation Using CO2 as CO Surrogate

Carbon dioxide is a sufficient and important carbon resource, which has been widely used as a C1 building block in synthetic chemistry. Carbonylations with CO are important processes in industry. However, due to the toxicity of CO, its storage and transport are problematic. Attentions are gradually focused on using other safe reagents to be the CO surrogates in carbonylation reactions. This review focuses on the summary of recent developments in using CO₂ as a CO surrogate in homogeneous catalysis. Reductive processes by using H₂, Si‐H, alcohols, etc and redox‐neutral processes are separately summarized.     

基于离子液体固定二氧化碳的研究进展

综述了不同种类离子液体吸收固定CO2的研究进展,从离子液体的结构和分子模拟结果探讨了离子液体吸收CO2的机理及特征,展望了功能化离子液体在固定CO2方面的应用前景并分析了其在工业应用中存在的问题.