Bio-inspired catalyst-driven efficient CO2 capture and subsequent mineralization in aqueous media under practical conditions

Abstract

Efficient carbon management and the successful implementation of innovative technologies are a necessity for environmental mitigation and the realization of a sustainable circular economy. Current carbon dioxide removal (CDR) and CO₂ capture and storage (CCS) technologies fail to meet the gigatonne-level CO₂ removal targets, lack profitability, and thus are not widely adopted/retrofitted in the current industrial settings. To address these issues, unique alternative solutions are required that possess the versatility for application in various CO₂-emitting industries, have economic viability, and do not cause secondary pollution effects. Our pursuit in this regard led to the development of a catalyst C1, inspired by the architectural design of the Carbonic anhydrase enzyme, where a Zn (II) ion is bound tetrahedrally at the N₃-primary coordination site and a peripheral ethereal O₃-site which functioned as the outer coordination sphere (OCS). This promoted the facile generation of the potent Zn-OH^– motif in near-neutral media for rapid hydrolysis of CO₂ in aqueous solution to carbonate and bicarbonate ions. Mineralization of this captured CO₂ was performed with the appropriate addition of Ca(II) ions leading to the formation of pure CaCO₃. Practical application and industrial relevance were established with CO₂ capture and mineralization experiments performed in seawater, flue-gas mixture with 15 % (v/v) CO₂, and air containing only 0.04 % (v/v) CO₂ in a separate set of experiments. The kinetic parameters and biomimetic nature of the metal complex C1 were confirmed through detailed pNPA hydrolysis studies. Our results indicate that bio-inspired catalysts can be a cost-effective, viable solution for mass-scale carbon mitigation and management strategy using only environmentally benign resources.