Water-Lean Solvents for Post-Combustion CO2 Capture: Fundamentals, Uncertainties, Opportunities, and Outlook

This review is designed to foster the discussion regarding the viability of postcombustion CO₂ capture by water-lean solvents, by separating fact from fiction for both skeptics and advocates. We highlight the unique physical and thermodynamic properties of notable water-lean solvents, with a discussion of how such properties could translate to efficiency gains compared to aqueous amines. The scope of this review ranges from the purely fundamental molecular-level processes that govern solvent behavior to bench-scale testing, through process engineering and projections of process performance and cost. Key discussions of higher than expected CO₂ mass transfer, water tolerance, and compatibility with current infrastructure are presented along with current limitations and suggested areas where further solvent development is needed. We conclude with an outlook of the status of the field and assess the viability of water-lean solvents for postcombustion CO₂ capture.

Direct Access to Primary Amines and Particle Morphology Control in Nanoporous CO2 Sorbents

Chemical tuning of nanoporous, solid sorbents for ideal CO₂ binding requires unhindered amine functional groups on the pore walls. Although common for soluble organics, post-synthetic reduction of nitriles in porous networks often fails due to insufficient and irreversible metal hydride penetration. In this study, a nanoporous network with pendant nitrile groups, microsphere morphology was synthesized in large scale. The hollow microspheres were easily decorated with primary amines through in situ reduction by widely available boranes. The CO₂ capture capacity of the modified sorbent was increased to up to four times that of the starting nanoporous network with a high heat of adsorption (98 kJ mol^-1 ). The surface area can be easily tuned between 1 and 354 m²  g^-1 . The average particle size (ca. 50 μm) is also quite suitable for CO₂ capture applications, such as those with fluidized beds requiring spheres of micron sizes.

Substituent dependence of imidazoline derivatives on the capture and release system of carbon dioxide

The imidazoline having a cyclic guanidine moiety only captured CO₂ quantitatively, and then the cyclic guanidine derivative gave the guanidinium bicarbonate by CO₂ fixation together with a slight amount of water.

Tuning organic carbon dioxide absorbents for carbonation and decarbonation

The reaction of carbon dioxide with a mixture of a superbase and alcohol affords a superbase alkylcarbonate salt via a process that can be reversed at elevated temperatures. To utilize the unique chemistry of superbases for carbon capture technology, it is essential to facilitate carbonation and decarbonation at desired temperatures in an easily controllable manner. Here, we demonstrate that the thermal stabilities of the alkylcarbonate salts of superbases in organic solutions can be tuned by adjusting the compositions of hydroxylic solvent and polar aprotic solvent mixtures, thereby enabling the best possible performances to be obtained from the various carbon dioxide capture agents based on these materials. The findings provides valuable insights into the design and optimization of organic carbon dioxide absorbents.

High capacity CO2sorbents based on zinc-functionalized ionic liquid confined in morphologically diverse porous matrices

High uptake capacity and dramatic sorption kinetic enhancement in a series of novel hybrid CO₂sorbents based on a supported zinc-functionalized ionic liquid.