Carbon dioxide capture and reduction are two of the important challenges of modern chemistry. To overcome them, basic nitrogen groups have been used as both a means of CO2 capture and as components of reduction catalysts. Some studies have also explored the effects different nitrogen-adjacent substituents can have on the efficacy of these capture and reduction systems. It is clear that CO2 reduction requires proton. Here, we supply them locally by studying the interaction between 2-Hydroxyquinoline (2-HQ) and CO2. Particular emphasis is placed on stabilization of the complex by proton transfer from an adjacent hydroxyl group to CO2. Geometry optimizations, potential energy scans and molecular dynamics reveal the existence of two separate potential wells for CO2 around the hydroxyquinoline compound. The first places CO2 at a distance of 2.9 Å from 2-HQ. In this arrangement neither molecule shows drastic structural changes. However, in the second, CO2 is stabilized in a well 1.47 Å from 2-HQ. Here, CO2 is no longer linear, instead it relaxes to an angle of 124 degrees and effectively forms a carbamate-like bond with 2-HQ. Importantly, we also observe that the hydroxyl proton effectively transfers to the CO2 oxygen. We show that the stability of the complex in the second well is likely caused by this proton transfer. This work sheds light on how hydrogen bonds and proton transfer can potentially help design molecules for efficient CO2 capture and reduction.

Importance of proton transfer in CO2 capture and reduction

251st National Meeting (2016)

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