Reactive capture and electrochemical conversion of CO2 with ionic liquids and deep eutectic solvents

Ionic liquids (ILs) and deep eutectic solvents (DESs) have tremendous potential for reactive capture and conversion (RCC) of CO2 due to their wide electrochemical stability window, low volatility, and high CO2 solubility. There is environmental and economic interest in the direct utilization of the captured CO2 using electrified and modular processes that forgo the thermal- or pressure-swing regeneration steps to concentrate CO2, eliminating the need to compress, transport, or store the gas. The conventional electrochemical conversion of CO2 with aqueous electrolytes presents limited CO2 solubility and high energy requirement to achieve industrially relevant products. Additionally, aqueous systems have competitive hydrogen evolution. In the past decade, there has been significant progress toward the design of ILs and DESs, and their composites to separate CO2 from dilute streams. In parallel, but not necessarily in synergy, there have been studies focused on a few select ILs and DESs for electrochemical reduction of CO2, often diluting them with aqueous or non-aqueous solvents. The resulting electrode-electrolyte interfaces present a complex speciation for RCC. In this review, we describe how the ILs and DESs are tuned for RCC and specifically address the CO2 chemisorption and electroreduction mechanisms. Critical bulk and interfacial properties of ILs and DESs are discussed in the context of RCC, and the potential of these electrolytes are presented through a techno-economic evaluation.

Solid-Liquid Host-Guest Composites: The Marriage of Porous Solids and Functional Liquids

Composite materials can provide remarkable improvements over the individual constituents. Especially, with a liquid component introduced into a solid porous host, solid-liquid host-guest composites have recently come to the forefront with exceptional functions that promise them for a wealth of applications. Combining the unprecedented dynamic, transparent, omniphobic, self-healing, diffusive and adaptive nature of functional liquid with inherent solid host's property, solid-liquid host-guest composites can realize the ease of fabrication, long-term stability, and a broad spectrum of enhanced properties, which cannot be fully met by conventional solid-solid composites or liquid-liquid composites. This review presents the state-of-the-art progress in solid-liquid host-guest composites. Initially, the concept, classification, design strategy, as well as fabrication methods as a path forward to develop the composites are unraveled, and further it is elaborated on how the functionality of porous solid and functional liquid can be harnessed to create composites with a broad range of unique properties, especially, the optical, thermal, electric, mechanical, sorption, and separation properties. With these fascinating properties, a myriad of emerging applications such as optical devices, thermal management, electromagnetic-interference shielding, soft electronics, gas capture and release, and multiphase separations are touched upon, inspiring more frontier researches in materials science, interfacial chemistry, membrane science, engineering, and multidisciplinary. Finally, this review provides the perspective on the future directions of solid-liquid host-guest composites and assesses the challenges and opportunities ahead.

Emerging trends in porous materials for CO2 capture and conversion

This review highlights the recent progress in porous materials (MOFs, zeolites, POPs, nanoporous carbons, and mesoporous materials) for CO₂ capture and conversion.

Natural rubber latex foam with particulate fillers for carbon dioxide adsorption and regeneration

To reduce the carbon dioxide (CO2) concentration in the atmosphere, natural rubber (NR) was developed as a rubber foam for CO2 adsorption. Although the CO2 adsorption capacity of the NR latex foam produced by mixing with a cake mixer (CM) was higher than that produced with an overhead stirrer (OS), both capacity values were still low. To improve the CO2 adsorption capacity, the use of unmodified and (3-aminopropyl)triethoxysilane-modified silica particles as fillers in the CM rubber foam matrix was examined. The highest CO2 adsorption capacity, from a mixed gas flow rate of 100 mL min-1 at ambient temperature and pressure, was obtained with the CM foam filled with 5 parts by weight per hundred parts of rubber filled with modified silica particles (4.08 mg g-1). The CO2 adsorption capacity of this foam was approximately 1.11- and 2.87-fold higher than that of the CM foam filled with unmodified silica particles (3.69 mg g-1) and unfilled CM rubber (1.42 mg g-1), respectively. Morphological analysis supported that the cell size and number of pores per cell of the NR latex foam, which were higher in the CM foams than the OS foams, were important factors for evaluating CO2 adsorption. In addition to physisorption between CM and CO2, chemisorption between the modified silica particles and CO2 increased the CO2 adsorption capacity.

Encapsulated Ionic Liquids for CO2 Capture: Using 1-Butyl-methylimidazolium Acetate for Quick and Reversible CO2 Chemical Absorption

The potential advantages of applying encapsulated ionic liquid (ENIL) to CO₂ capture by chemical absorption with 1-butyl-3-methylimidazolium acetate [bmim][acetate] are evaluated. The [bmim][acetate]-ENIL is a particle material with solid appearance and 70 % w/w in ionic liquid (IL). The performance of this material as CO₂ sorbent was evaluated by gravimetric and fixed-bed sorption experiments at different temperatures and CO₂ partial pressures. ENIL maintains the favourable thermodynamic properties of the neat IL regarding CO₂ absorption. Remarkably, a drastic increase of CO₂ sorption rates was achieved using ENIL, related to much higher contact area after discretization. In addition, experiments demonstrate reversibility of the chemical reaction and the efficient ENIL regeneration, mainly hindered by the unfavourable transport properties. The common drawback of ILs as CO₂ chemical absorbents (low absorption rate and difficulties in solvent regeneration) are overcome by using ENIL systems.

Ammonia capture from the gas phase by encapsulated ionic liquids (ENILs)

Encapsulated ionic liquids (ENILs) based on carbonaceous submicrocapsules were designed, synthesized and applied to the sorption of NH₃ from gas streams.