An interesting contribution to solving the climate crisis involves the use of CO2 as a feedstock for monomers to produce sustainable plastics. In the European Horizon 2020 project "OCEAN" a continuous multistep process from CO2 to oxalic acid and derivatives is developed, starting with the electrochemical reduction of CO2 to potassium formate. The subsequent formate-to-oxalate coupling is a reaction that has been studied and commercially used for over 150 years. With the introduction of superbases as catalysts under moisture-free conditions unprecedented improvements were shown for the formate coupling reaction. With isotopic labelling experiments the presence of carbonite as an intermediate was proven during the reaction, and with a unique operando set-up the kinetics were studied. Ultimately, the required reaction temperature could be dropped from 400 to below 200 °C, and the reaction time could be reduced from 10 to 1 min whilst achieving 99 % oxalate yield.
Keywords: CO2 conversion; formate coupling; hydrides; polyester monomers; superbase catalysts.
© 2021 The Authors. ChemSusChem published by Wiley-VCH GmbH.