CO₂-Induced Miscibility of Fluorous and Organic Solvents for Recycling Homogeneous Catalysts

Abstract

Fluorous biphasic chemistry enables the recovery of homogeneous catalysts but presents engineering challenges because of issues concerning phase contacting and solvent loss. The addition of gaseous CO2 to fluorous−organic biphasic systems results in a single homogeneous liquid phase at temperatures well below the upper critical solution temperature of the binary liquid mixture. This phenomenon is due to the high solubility of CO2 in both organic liquids and fluorocarbons, and it facilitates reactions and can also reduce fluorous solvent losses. We demonstrate two homogeneously catalyzed reactions, a hydrogenation and an epoxidation, which result in an enhancement in the turnover frequency of 70% and 50%, respectively, for the CO2-merged phase relative to the fluorous biphasic system. This creates new opportunities for the use of fluorous-sequestered catalysts.