2019 Engineering Sustainable Development

Electrochemical Coupling of Aromatic Alcohols and Carbon Dioxide for Electrosynthesis of ?-Hydroxy Acids in a Sustainable Way

Authors

Kim, M. - Presenter, Korea Institute of Energy Research
Muchez, L., KU Leuven
Vos, D. D., KU Leuven
The chemical incorporation of CO2 into organic molecules will be an effective approach for sustainable low carbon society. Carboxylation is one of the best way to make C-C bond through the reaction of CO2 with organic molecules. However, CO2 is highly thermodynamically stable, in order to activate it, carboxylation often demands harsh reaction conditions, such as high temperature and high pressure, and environmentally harmful organometallic catalysts. An electrochemical route for carboxylation can be free from these issues by using electrons as a redox reagent. The electrosynthesis of carboxylic acid is a highly promising method in organic synthesis from the viewpoint of green chemistry and CO2 utilization.

For a sustainable electrosynthesis of carboxylic acid, herein, we report a novel methodology operating in a simple undivided cell with a non-sacrificial anode, at which tetramethylpiperidine-1-oxyl (TEMPO)-mediated alcohol oxidation takes place. Aromatic alcohols can be oxidized with high efficiency to ketones or aldehydes at the anode in the presence of a small amount of water, and then converted to α-hydroxy acids in yields of up to 61 % by coupling with CO2 at the cathode. The electrocarboxylation mechanism comprising electron and proton transfers at the cathode is discussed along with experiments using various cathode materials. Electron and proton transfers are influenced by the hydrogen adsorption energy of the cathode material, which plays an important role in the electrocarboxylation efficiency.