Carbon Dioxide Hydrogenation to Formic Acid with Self-Separating Product and Recyclable Catalyst Phase

The homogeneously catalyzed hydrogenation of carbon dioxide to formic acid is a promising route for carbon dioxide utilization and power-to-X concepts. Separation of the product and the catalyst under retention of the performance of the catalyst remains a major challenge, however. Herein, we present a Ru-phosphine catalyzed reaction system comprising only a hydrophobic solvent as the catalyst phase and N-methyldiethanolamine as a base. The formation of formic acid causes a spontaneous separation of the monophasic reaction mixture into a pure formic acid/amine product and a recyclable catalyst phase. By optimizing the reaction conditions, a turnover number of 1590 in a single reaction and a total turnover number of 5590 after four recycling runs were achieved.