Preorganization and Cooperation for Highly Efficient and Reversible Capture of Low-Concentration CO2 by Ionic Liquids

Effectiveness of ionic liquid-supported membranes for carbon dioxide capture: a review

The world's population explosion creates a need for natural resources for energy, which will become a significant contributor to global climate change. As we all know, carbon dioxide (CO₂) is one of the most critical elements of the global greenhouse gas effect. CO₂ capture and storage innovations have piqued researchers' attention in recent decades. Compared to other methods, membrane separation has some positive performance in CO₂ capture. CO₂ capture with membrane separation using enhanced ionic liquids (ILs) is described in this review. ILs have made an appearance in CO₂ capture work as the potential additive, and companies and academics have been interested in CO₂ separation for the past two decades. This article comprehensively analyzes the current modern approach in ILs and IL-based membranes for gas separation processes. Based on the latest literature and performance data, this work provides a complete compressive examination of types of ILs and IL-supported membrane performances. ILs for CO₂ capture were also explored, and IL-based membranes for different ILs were also studied. This study emphasizes the supremacy of novel ILs for CO₂ capture in membrane separation.

The Nature of Carbon Dioxide in Bare Ionic Liquids

Ionic liquids (ILs) are among the most studied and promising materials for selective CO₂ capture and transformation. The high CO₂ sorption capacity associated with the possibility to activate this rather stable molecule through stabilization of ionic/radical species or covalent interactions either with the cation or anion has opened new avenues for CO₂ functionalization. However, recent reports have demonstrated that another simpler and plausible pathway is also involved in the sorption/activation of CO₂ by ILs associated with basic anions. Bare ILs or IL solutions contain almost invariable significant amounts of water and through interaction with CO₂ generate carbonates/bicarbonates rather than carbamic acids or amidates. In these cases, the IL acts as a base and not a nucleophile and yields buffer-like solutions that can be used to shift the equilibrium toward acid products in different CO₂ reutilization reactions. In this Minireview, the emergence of IL buffer-like solutions as a new reactivity paradigm in CO₂ capture and activation is described and analyzed critically, mainly through the evaluation of NMR data.

Development of High-Capacity and Water-Lean CO2 Absorbents by a Concise Molecular Design Strategy through Viscosity Control

The exponentially increasing viscosity of water-lean CO₂ absorbents during carbon capture processes is a critical problem for practical application, owing to its strong correlation with systems' mass transfer properties, as well as convenience of transportation. In this work, a concise strategy based on structure-viscosity relationships is proposed and applied to construct a series of functionalized ethylenediamines as single-component absorbents for post-combustion CO₂ capture. These nonaqueous absorbents have outstanding viscosities (50-200 cP, 25 °C) at their maximal CO₂ capacities (up to 22 wt % or 4.92 mol kg^-1 , 1 bar), and are readily regenerated at low temperatures (50-80 °C) under ambient pressure. Additional capture of CO₂ through physisorption could also be achieved by operating at high pressures. The CO₂ capture and release process is systematically investigated by means of ¹³ C NMR spectroscopy, differential scanning calorimetry (DSC), in situ FTIR analysis, and density functional theory (DFT) calculations, which could provide sufficient spectroscopic details to reveal the ease of reversibility and enable rational interpretation of the absorption mechanism.

Reply to the Correspondence on "Preorganization and Cooperation for Highly Efficient and Reversible Capture of Low-Concentration CO2 by Ionic Liquids"

The water content is crucial to the preparation of [P₄₄₄₂ ][Suc] and its capture of CO₂ . The use of a large amount of water in the preparation of this ionic liquid results in the significant formation of the byproduct succinamate anions and difficulties in water removal, which strongly reduces the capacity of CO₂ absorption through a bicarbonate mechanism. By contrast, the addition of a small amount of water maintains a high absorption capacity through cooperation.

Correspondence on "Preorganization and Cooperation for Highly Efficient and Reversible Capture of Low-Concentration CO2 by Ionic Liquids"

The preorganization and cooperation mechanism of imide-based ionic liquids reported in a recent Communication was evocated to rationalize the extremely high gravimetric CO₂ capture displayed by these fluids. An analysis of the reported spectroscopic evidences together with additional experiments led to the proposition of an alternative, simpler, and feasible mechanism involving the formation of bicarbonate.

New crown ether complex cation ionic liquids with N-heterocycle anions: preparation and application in CO2 fixation

A series of CECILs have been devised, synthesized and characterized by NMR, IR, elemental analysis and TGA-DSC.