Catalysis in inverted supercritical CO2/aqueous biphasic media

A new inverted biphasic catalysis system using supercritical CO2 as the stationary catalyst phase and water as the continuous phase is described for Rh-catalysed hydroformylation of polar substrates. Product separation and catalyst recycling is possible without depressurising the autoclave. Turnover numbers of up to 3560 were obtained in three consecutive runs and Rh leaching into the aqueous phase was below 0.3 ppm. The absence of organic solvents allows convenient product isolation from the aqueous layer without the need for waste water treatment.