Abstract
Using small organic molecular redox carriers to reversibly capture CO(2) and convert it to carbon-based chemicals is a promising approach to mitigate the ongoing climate crisis. 2,1,3-benzothiadiazole (BT) is an interesting unit due to its proven interaction with CO(2) upon reduction and the ease of tuning its structure. In this work, by introducing two CN in BT, the molecule 2,1,3-benzothiadiazole-4,7-dicarbonitrile (BTDN) has multiple reduced states as compared to BT and is found to interact with CO(2) at multiple reduced states. The work is carried out with a combination of (spectro-)electrochemical and computational studies. Cyclic voltammetry experiments in the presence of CO(2) show a clear interaction between BTDN and CO(2) upon the second reduction of BTDN and a large current increase at the third reduction. Density functional theory calculations prove a large variety of possible CO(2)-bound species that can match the experimental data. The binding of CO(2) on BTDN is found to be reversible upon the oxidation of the species, especially with low concentrations of CO(2). From NMR and IR experiments, certain amount of reduced product - oxalate is detected after bulk electrolysis at the third reduction potential in the presence of CO(2), showing the potential toward electrocatalysis after structural tuning and systematical optimization.