Tertiary Amine-Assisted Electroreduction of Carbon Dioxide to Formate Catalyzed by Iron Tetraphenylporphyrin

The reduction of CO2 by electrogenerated Fe(0)TPP can be directed toward formate with a good selectivity (ca. 70%) upon addition of a tertiary amine in the presence of a weak proton donor. Whereas most systems generating formate from CO2 involve the initial formation of a hydride, we demonstrate herein that the hydride pathway is avoided by preferential binding of CO2 that may then be protonated by weak acids. The net result is that hydrogen production via the hydride is disfavored, thus leading to high yields of formate. These results demonstrate an alternative route for the activation of CO2 to formate.