The rising atmospheric concentration of carbon dioxide (CO2) is assumed to be a key factor in global climate change, requiring robust and sustainable carbon conversion technologies. While carbonic anhydrase (CA) is a highly efficient enzyme for CO2 sequestration, its industrial application is limited by stability, cost, and scalability challenges. To address these limitations, we developed a CA-mimetic metal-amino acid (Phe-Zn(II)) bionanozyme featuring amyloid-like supramolecular cross-β-sheet architecture that provides high structural stability and recyclability. Gas chromatography (GC) analysis of a continuous flow bubble reactor charged with Phe-Zn(II) bionanozyme exhibits a CO2 conversion efficiency of approximately 18% in an aqueous medium (pH 7.0, 25 °C, ambient pressure), while maintaining remarkable structural integrity as confirmed by postcatalysis PXRD analysis. The amyloid-like supramolecular cross-β-sheet architecture, stabilized by π-π stacking and intermolecular hydrogen bonding, generates a confined catalytic microenvironment that enhances Zn(II) Lewis's acidity and promotes efficient CO2 hydration, which is crucial compared to previous reports. Next, density functional theory (DFT) calculations reveal a three-step catalytic pathway involving hydroxide ion generation, nucleophilic attack, and carbonic acid formation, with a rate-determining barrier of 12.3 kcal/mol, making the reaction feasible at room temperature. We also investigated the impact of different amino acids coordinated with Zn, finding that Phe-Zn(II) shows higher catalytic activity. This is due to the stronger electron-withdrawing effect of the phenyl group, which enhances the Lewis acidity of Zn2+, activates the Zn2+-OH2 bond, and lowers the rate-determining barrier. Taken together, the combination of experimental catalysis, structural robustness, and mechanistic validation highlights Phe-Zn(II) as a promising, cost-effective, and minimalistic catalyst yet efficient carbonic anhydrase mimic for CO2 conversion, paving the way for scalable and sustainable carbon sequestration strategies critical for mitigating climate change.
Ramesh et al. (Thu,) studied this question.