Nanoparticulate TiO2-Supported Double Metal Cyanide Catalyst for the Copolymerization of CO2 with Propylene Oxide

A titanium oxide supported double metal cyanide (TiO2‐DMC) was found to be a highly active catalyst for the reaction of CO2 with propylene oxide to polyethercarbonates, which are useful polymer building blocks for polyurethane applications. The catalyst was prepared by coprecipitation of potassium hexacyanocobaltate(III) and titanium(IV) ethoxide with an excess amount of ZnCl2 under slightly acidic conditions. The TiO2‐DMC catalyst provided excellent selectivity to the polymer (>97 %) and outstanding productivity (>500 gpolymer/gcatalyst). The TiO2‐support enhanced the Lewis acidity of the DMC catalyst, which facilitated activation of the epoxide and adjusted the binding strength of the polymer chain to the surface of the catalyst. CO2 is utilized as a renewable resource in the copolymerization with epoxides to polyethercarbonates. The excellent chemoselectivity of the nanoparticulate TiO2‐supported double metal cyanide catalyst is rationalized by the Lewis acidity of the TiO2 support. The polyethercarbonate is characterized by a large fraction of carbonate linkages in segments with a nonalternating sequence of co‐monomers.