Congmin Wang

Tuning the Basicity of Ionic Liquids for Equimolar CO2 Capture

Basic ionic liquids (ILs) based on a phosphonium hydroxide derivative can be tuned for CO{sub 2} capture by varying the weak proton donors, which have different pK{sub a} values. The stability, absorption capacity, and absorption enthalpy of the ILs could be easily tuned: the best IL for CO{sub 2} capture has good stability (>300 C), energy saving (ca. 56 kJ mol{sup -1}), and equimolar absorption capability.

Carbon Dioxide Capture by Superbase-Derived Protic Ionic Liquids†

Protic ionic liquids (PILs) from a superbase and fluorinated alcohol, imidazole, pyrrolinone, or phenol were designed to capture CO{sub 2} based on the reactivity of their anions to CO{sub 2}. These PILs are capable of rapid and reversible capture of about one equivalent of CO{sub 2}, which is superior to those sorption systems based on traditional aprotic ILs.

A Superacid-Catalyzed Synthesis of Porous Membranes Based on Triazine Frameworks for CO2 Separation

A general strategy for the synthesis of porous, fluorescent, triazine-framework-based membranes with intrinsic porosity through an aromatic nitrile trimerization reaction is presented. The essence of this strategy lies in the use of a superacid to catalyze the cross-linking reaction efficiently at a low temperature, allowing porous polymer membrane architectures to be facilely derived. With functionalized triazine units, the membrane exhibits an increased selectivity for membrane separation of CO(2) over N(2). The good ideal CO(2)/N(2) selectivity of 29 ± 2 was achieved with a CO(2) permeability of 518 ± 25 barrer. Through this general synthesis protocol, a new class of porous polymer membranes with tunable functionalities and porosities can be derived, significantly expanding the currently limited library of polymers with intrinsic microporosity for synthesizing functional membranes in separation, catalysis, and energy storage/conversion.

Equimolar CO2 capture by imidazolium-based ionic liquids and superbase systems

Imidazolium-based ionic liquids continue to attract interest in many areas of chemistry because of their low melting points, relatively low viscosities, ease of synthesis, and good stabilities against oxidative and reductive conditions. However, they are not totally inert under many conditions due to the intrinsic acidity of hydrogen at the C-2 position in the imidazolium cation. In this work, this intrinsic acidity was exploited in combination with an organic superbase for the capture of CO2 under atmospheric pressure. During the absorption of CO2, the imidazolium-based ionic liquid containing an equimolar superbase reacted with CO2 to form a liquid carboxylate salt so that the equimolar capture of CO2 with respect to the base was achieved. The effects of ionic liquid structures, types of organic superbases, absorption times, and reaction temperatures on the capture of CO2 were investigated. Our results show that this integrated ionic liquid–superbase system is capable of rapid and reversible capture of about 1 mol CO2 per mole of ionic liquid. Furthermore, the captured CO2 can be readily released by either heating or bubbling N2, and recycled with little loss of its capture capability. This efficient and reversible catch-and-release process using the weak acidity of the C-2 proton in nonvolatile imidazolium-based ionic liquids provides a good alternative to the current CO2 capture methods that use volatile alkanols, amines, or water.

Novel quaternary ammonium ionic liquids and their use as dual solvent-catalysts in the hydrolytic reaction

Ionic liquids (ILs) are no longer just a class of esoteric compounds, but are proving to be valuable and useful in a multitude of different applications. Herein, novel quaternary ammonium ionic liquids have been synthesized and characterised. These ionic liquids are Bronsted acidic, available from cheap raw materials and easy to prepare. They have been used both as a catalyst and environmentally benign solvent for the hydrolytic reaction of 1,1,1,3-tetrachloro-3-phenylpropane, eliminating the need for a volatile organic solvent and additional catalyst. The results clearly demonstrate that these ILs can be easily separated and reused without losing their activity and quality. Also, the yields obtained with this methodology are significantly increased in comparison with those reported in organic solvents to date.

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.

Reversible and robust CO2 capture by equimolar task-specific ionic liquid–superbase mixtures

Integrated sorption systems consisting of 1 : 1 mixtures of an alcohol-functionalized ionic liquid and a superbase were found to be effective for CO2 capture under atmospheric pressure, eliminating the use of volatile n-alkanols or water. Conversely, by using the current approach, there is no longer a requirement for maintaining scrupulously dry conditions. The effect of ionic liquid structure, choice of superbase, their relative ratios, the sorption temperature, and the reaction time on the absorption and release of CO2 were investigated. Our results demonstrate that (i) this integrated ionic liquid–superbase system is capable of rapid and reversible capture of nearly one mole of CO2 per mole of superbase, (ii) the captured CO2 can be readily released by either mild heating or bubbling with an insert gas (N2, Ar), and (iii) this novel CO2 chemisorption platform can be recycled with minimal loss of activity. This efficient and fully reversible catch-and-release process using non-volatile, task-specific ionic liquids provides an excellent alternative to current CO2 capture technologies, which are based largely around volatile alkanols or alkylamines. Furthermore, our integrated ionic liquid–superbase system can be used as a novel medium for supported liquid membranes, for which they demonstrate both good selectivity and permeability in model CO2/N2 gas separations.

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.

Tuning the Physicochemical Properties of Diverse Phenolic Ionic Liquids for Equimolar CO2 Capture by the Substituent on the Anion

Phenolic ionic liquids for the efficient and reversible capture of CO(2) were designed and prepared from phosphonium hydroxide and substituted phenols. The electron-withdrawing or electron-donating ability, position, and number of the substituents on the anion of these ionic liquids were correlated with the physicochemical properties of the ionic liquids. The results show that the stability, viscosity, and CO(2)-capturing ability of these ionic liquids were significantly affected by the substituents. Furthermore, the relationship between the decomposition temperature, the CO(2)-absorption capacity, and the basicity of these ionic liquids was quantitatively correlated and further rationalized by theoretical calculation. Indeed, these ionic liquids showed good stability, high absorption capacity, and low absorption enthalpy for CO(2) capture. This method, which tunes the physicochemical properties by making use of substituent effects in the anion of the ionic liquid, is important for the design of highly efficient and reversible methods for CO(2)-capture. This CO(2) capture process using diverse phenolic ionic liquids is a promising potential method for CO(2) absorption with both high absorption capacity and good reversibility.

Preparation of simple ammonium ionic liquids and their application in the cracking of dialkoxypropanes

Owing to the unique advantages of ionic liquids, the preparation and industrial application of ionic liquids have attracted considerable interest. Herein, we report that a series of simple ammonium ionic liquids has been synthesized and characterised. These ionic liquids are air and water stable, easy to prepare from amine and acid, and relatively cheap. They have been used as catalysts and environmentally benign solvents for the cracking reactions of dialkoxypropanes, eliminating the need for volatile organic solvents and additional catalysts. The results clearly demonstrate that these ionic liquids can be easily separated and reused without losing their activity and quality. Furthermore, the conversion and selectivity obtained with this method are significantly increased in comparison with those reported in traditional organic solvents to date. These ionic liquids provide a good alternative way for the synthesis of alkoxypropenes.