Guokai Cui

Highly Efficient and Reversible SO2 Capture by Tunable Azole-based Ionic Liquids through Multiple-Site Chemical Absorption

A novel strategy for SO(2) capture through multiple-site absorption in the anion of several azole-based ionic liquids is reported. An extremely high capacity of SO(2) (>3.5 mol/mol) and excellent reversibility (28 recycles) were achieved by tuning the interaction between the basic anion and acidic SO(2). Spectroscopic investigations and quantum-mechanical calculations showed that such high SO(2) capacity originates from the multiple sites of interaction between the anion and SO(2). These tunable azole-based ionic liquids with multiple sites offer significant improvements over commonly used absorbents, indicating the promise for industrial applications in acid gas separation.

Significant Improvements in CO2Capture by Pyridine-Containing Anion-Functionalized Ionic Liquids through Multiple-Site Cooperative Interactions

A strategy for improving CO2 capture by new anion-functionalized ionic liquids (ILs) making use of multiple site cooperative interactions is reported. An extremely high capacity of up to 1.60 mol CO2 per mol IL and excellent reversibility were achieved by introducing a nitrogen-based interacting site on the phenolate and imidazolate anion. Quantum-chemical calculations, spectroscopic investigations, and calorimetric data demonstrated that multiple-site cooperative interactions between two kinds of interacting sites in the anion and CO2 resulted in superior CO2 capacities, which originated from the π-electron delocalization in the pyridine ring.

Highly efficient SO2 capture by dual functionalized ionic liquids through a combination of chemical and physical absorption.

Two kinds of dual functionalized ionic liquids with ether-functionalized cations and tetrazolate anions were designed, prepared, and used for SO(2) capture, which exhibit an extremely high SO(2) capacity and excellent reversibility through a combination of chemical and physical absorption.

Highly efficient CO2 capture by tunable alkanolamine-based ionic liquids with multidentate cation coordination

A series of novel alkanolamine-based ionic liquids show a highly efficient and excellent reversible capture of CO(2) through multidentate cation coordination between alkanolamine and Li(+) ion in a quasi-aza-crown ether fashion.

Highly efficient SO2 capture by phenyl-containing azole-based ionic liquids through multiple-site interactions

Ionic liquids are suitable for the absorption of acid gases such as SO2 because of their unique properties. In this work, a new method was developed for the highly efficient capture of SO2 by introducing a phenyl group into the azole-based ionic liquids. It was found that these phenyl-containing azole-based ionic liquids reacted with SO2 through multiple-site interactions between the anion and SO2, resulting in an extremely high SO2 capacity of up to ∼5.7 mole per mole ionic liquid. Spectroscopic investigations and quantum calculations show that the dramatic enhancement in the SO2 capacity originated from the enhanced π⋯S interaction between the phenyl group on the anion and SO2. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the ionic liquid. This efficient and reversible process using these phenyl-containing azole-based ionic liquids with an enhanced π⋯S interaction provides an excellent alternative to current SO2 capture technologies.

Highly efficient and reversible CO2 adsorption by amine-grafted platelet SBA-15 with expanded pore diameters and short mesochannels

The ever-increasing concentration of CO2 in the atmosphere has raised great concerns over carbon capture techniques. To enhance the CO2 adsorption capacity, a kind of platelet SBA-15 with short channels and large pore diameters has been prepared and grafted with various aminosilanes (mono-, di-, and tri-amine). Thorough analysis of the support structure and sorbent performance was estimated through a combination of amine loading, CO2 adsorption capacity and CO2/N2 selectivity. It was shown that compared to traditional fiber SBA-15, amine loading for these novel sorbents was increased from 3.56 to 5.90 mmol g−1 (a 66% increase), and the CO2 adsorption capacity was increased from 1.23 to 2.67 mmol g−1 (a 120% increase). Also, the selectivity of CO2/N2 was remarkably enhanced from 37 to 169. The CO2 adsorption enthalpy reached 67 kJ mol−1. Moreover, these sorbents are regenerable and exhibit good stabilities. Thus, this approach offers an alternative for the development of technological innovation towards efficient and reversible processes for carbon capture.

Reversible Hydrophobic–Hydrophilic Transition of Ionic Liquids Driven by Carbon Dioxide

Ionic liquids (ILs) with a reversible hydrophobic-hydrophilic transition were developed, and they exhibited unique phase behavior with H2O: monophase in the presence of CO2, but biphase upon removal of CO2 at room temperature and atmospheric pressure. Thus, coupling of reaction, separation, and recovery steps in sustainable chemical processes could be realized by a reversible liquid-liquid phase transition of such IL-H2O mixtures. Spectroscopic investigations and DFT calculations showed that the mechanism behind hydrophobic-hydrophilic transition involved reversible reaction of CO2 with anion of the ILs and formation of hydrophilic ammonium salts. These unique IL-H2O systems were successfully utilized for facile one-step synthesis of Au porous films by bubbling CO2 under ambient conditions. The Au porous films and the ILs were then separated simultaneously from aqueous solutions by bubbling N2, and recovered ILs could be directly reused in the next process.

Tuning the Basicity of Cyano‐Containing Ionic Liquids to Improve SO2 Capture through Cyano–Sulfur Interactions

A new approach has been developed to improve SO2 sorption by cyano-containing ionic liquids (ILs) through tuning the basicity of ILs and cyano-sulfur interaction. Several kinds of cyano-containing ILs with different basicity were designed, prepared, and used for SO2 capture. The interaction between these cyano-containing ILs and SO2 was investigated by FTIR and NMR methods. Spectroscopic investigations and quantum chemical calculations showed that dramatic effects on SO2 capacity originate from the basicity of the ILs and enhanced cyano-sulfur interaction. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the ILs. This efficient and reversible process, achieved by tuning the basicity of ILs, is an excellent alternative to current technologies for SO2 capture.

Tuning the Hydrophilicity and Hydrophobicity of the Respective Cation and Anion: Reversible Phase Transfer of Ionic Liquids.

The separation and recycling of catalyst and cocatalyst from the products and solvents are of critical importance. In this work, a class of functionalized ionic liquids (ILs) were designed and synthesized, and by tuning the hydrophilicity and hydrophobicity of cation and anion, respectively, these ILs could reversibly transfer between water and organics triggered upon undergoing a temperature change. From a combination of multiple spectroscopic techniques, it was shown that the driving force behind the transfer was originated from a change in conformation of the PEG chain of the IL upon temperature variation. By utilizing the novel property of this class of ILs, a highly efficient and controllable CuI-catalyzed cycloaddition reaction was achieved wherein the IL was used to entrain, activate, and recycle the catalyst, as well as to control the reaction.

Highly efficient and reversible SO2 capture by halogenated carboxylate ionic liquids

Because of the unique properties of ionic liquids, it has been suggested that ionic liquids, especially functionalized ionic liquids, could be used as good solvents for the capture of acidic gases such as SO2. In this work, a kind of carboxylate ionic liquid with a halogen atom on the alkyl chain of the carboxylate anion was developed for highly efficient and reversible capture of SO2 through multiple-site interactions. It was found that these halogenated carboxylate ionic liquids improved SO2 capture performance as well as being reversible. Spectroscopic investigations and quantum chemical calculations show that the enhancement in SO2 capacity originated from the halogen sulfur interaction between the halogen group on the carboxylate anion and SO2. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the SO2-saturated ionic liquids. This highly efficient and reversible process using halogenated carboxylate ionic liquids through adding a halogen group to the carboxylate anion provides an excellent alternative to current SO2 capture technologies.