Borate-Catalyzed Carbon Dioxide Hydration via the Carbonic Anhydrase Mechanism

The hydration of CO2 plays a critical role in carbon capture and geoengineering technologies currently under development to mitigate anthropogenic global warming and in environmental processes such as ocean acidification. Here we reveal that borate catalyzes the conversion of CO2 to HCO3 – via the same fundamental mechanism as the enzyme carbonic anhydrase, which is responsible for CO2 hydration in the human body. In this mechanism the tetrahydroxyborate ion, B(OH)4 –, is the active form of boron that undergoes direct reaction with CO2. In addition to being able to accelerate CO2 hydration in alkaline solvents used for carbon capture, we hypothesize that this mechanism controls CO2 uptake by certain saline bodies of water, such as Mono Lake (California), where previously inexplicable influx rates of inorganic carbon have created unique chemistry. The new understanding of CO2 hydration provided here should lead to improved models for the carbon cycle in highly saline bodies of water and to advances in carbon capture and geoengineering technology.