Enhancing CO2 absorption for post-combustion carbon capture via zinc-based biomimetic catalysts in industrially relevant amine solutions

Abstract

Anthropogenic greenhouse gas emissions, such as CO2 from fossil fuel combustion, are a global environmental, health, and economic concern. Aqueous amine-based CO2 capture processes offer a technologically mature and relevant approach to CO2 sequestration, although cost reduction strategies are still necessary for widespread deployment. Inspired by the metalloenzyme carbonic anhydrase (CA), we report the design, synthesis, and activity testing of zinc(II) complexes [ZnII(PSAAMP)Cl2] (1) and [ZnII(PSAMEA)Cl2] (2) as CO2 hydration catalysts in aqueous amine solutions. The novel multifunctional ligand environment includes features in the primary and secondary coordination spheres that result in enhanced CO2 mass transfer in industrially relevant carbon capture solvents and stability towards harsh industrial process conditions. Complexes that lack these key features do not show enhanced CO2 absorption. Density functional theory (DFT) calculations that assess the catalytic pathway demonstrate how 1 and 2 catalyze CO2 hydration analogous to CA. These catalysts increase mass transfer by 20–55% in lab scale experiments, offering the potential to reduce the cost of amine-based CO2 capture processes without significantly altering industrial-scale system design, making rapid deployment of this critical bridge technology a viable strategy to reduce global greenhouse gas emissions.