Absorption of carbon dioxide by aqueous amine solvents is a mature baseline technology for point-source CO2 capture because of its high capture efficiency and relatively low cost. A key question remaining is how to further reduce the cost of CO2 capture to make it more attractive for industrial-scale deployment. Liquid-to-solid phase-transition solvents have been introduced to reduce the regeneration energy. This concept is also investigated here by employing CO2-reactive amine molecules and sodium ions in aqueous media to form a supramolecular CO2–amine–salt fractal network via molecular interactions. Aqueous amines capture CO2 and form carbamate salt of ammonium cations. The CO2-responsive building unit is activated to chelate sodium chloride ions. Once supramolecular networks are formed, solid-phase formation and sedimentation occur, and the sediment is easily separated from the aqueous medium. The CO2–amine–salt precipitate is salted out from the solution in the form of NaHCO3 and an oligomer crystalline species. Decomposition of this solid material occurs at approximately 100°C, resulting in Na2CO3 and organics associated with CO2 release. The decomposed complex is then dissolved back to the aqueous solution. Because of the minimized amount of diluent in the solid network, the supramolecular network releases CO2 with minimum heat, offering a potential system for thermal energy reduction in CO2 capture, with a regeneration energy less than 2.0 MJ/kg CO2.

CO2 Capture mediated by supramolecular amine-salt network for low regeneration energy

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