Metal Oxide Supported Double Metal Cyanide Catalysts Modified by Group 13 Oxides for the Ring‐Opening Polymerization of Epoxides: Mechanistic Insights

The ring‐opening polymerization (ROP) of epoxides is an important industrial route to polyether polyols used in polyurethane and surfactant value chains. Double metal cyanide (DMC) catalysts provide high activity but often show an induction period and may require promoter additives. Here, we report metal oxide modified multimetal cyanide (MMC) catalysts of general formula [MxOy]n–Zn3[Co(CN)6]2 (M = Al, Ga, In), prepared by adding Group 13 alkoxides during ZnCl2/K3Co(CN)6 precipitation in tert‐butyl alcohol. XRF, STEM‐EDS, and XRD confirm incorporation and dispersion of Group 13 oxide phases on a largely amorphous DMC framework. In semi‐batch propoxylation of dipropylene glycol, normalized to cobalt loading (~10 ppm Co), the modified catalysts show much shorter activation times (≤10 min for Ga‐containing MMCs versus 55 min for unmodified Zn–Co DMC) and faster propylene oxide uptake. Kinetic analysis at comparable equivalent weight (~400 Da) shows up to 3.2‐fold higher apparent first‐order PO consumption rates for Ga‐modified MMCs. DFT/NBO analysis indicates that stronger Lewis acidity increases O—H bond polarization, supporting alcohol O–H activation as the rate‐determining step and explaining the improved activity trends.