DFT study on the mechanism of the CO2-to-CO conversion by Co-quaterpyridine complexes

Abstract

The electrochemical reduction of carbon dioxide has recently attracted global research interests as it can facilitate a sustainable low-temperature redox cycle for energy storage and conversion. Co-quaterpyridine complexes are one kind of the most promising molecular catalysts for highly selective electrochemical CO2‑to‑CO conversion at a very low overpotential. In the present work, the geometry, electronic structure and catalytic property of Co-quaterpyridine complexes were theoretically calculated through density functional theory (DFT). It is found that the initial catalyst [CoII(qpy)]2+ is reduced to neutral Co0(qpy) after receiving two electrons, and only this neutral species can bind and activate carbon dioxide in the presence of weak Brönsted acids effectively. More intriguingly, the catalyst finally recovers to [Co(qpy)CO]2+ due to the easy release of the formed product CO. Furthermore, the photo-physical properties of some important intermediates involved in the reaction were also investigated using the time-dependent density functional theory (TD-DFT).