Biomimetic Carbon Nanotube for Catalytic CO2 Hydrolysis: First-Principles Investigation on the Role of Oxidation State and Metal Substitution in Porphyrin

Hydrolysis of carbon dioxide is an important reaction for CO2 collection. Using accurate first-principles electronic structure calculations, we predict how the catalytic hydrolysis reaction in carbonic anhydrase (CA) can be mimicked in a metal porphyrin carbon nanotube. The two-step catalytic process can be improved remarkably by controlling the porphyrin oxidation state via the nanotube charge state and by substituting the porphyrin metal atom. The oxidation state and the metal substitution both have profound effects on the reaction energetics for the initial hydration reaction step. For the subsequent product-release reaction step, two different reaction mechanisms could take place. These mechanisms are distinctively sensitive to either the oxidation state change or the metal substitution, but not to both. For the overall catalytic cycle, a significant dependence on the nanotube charge state at low pH and on the metal substitution at high pH is expected.