Alternating copolymerization of carbon dioxide and cyclohexene oxide catalyzed by silicon dioxide/ZnCoIII double metal cyanide complex hybrid catalysts with a nanolamellar structure

Air‐stable hybrid catalysts of silicon dioxide/double metal cyanide complexes (Si‐DMCCs) based on Zn3[Co(CN)6]2 (ZHCC) were prepared by an in situ sol–gel method. The Si‐DMCCs showed low crystallinity and a nanolamellar structure with a thickness of ∼40–60 nm. In particular, a lamellar structure of regular hexagonal shape was observed for Si‐DMCCs with low SiO2 content. These catalysts had very high catalytic activity for alternating copolymerization of cyclohexene oxide (CHO) and carbon dioxide. A turnover number of 11,444, turnover frequency of 3815 h−1, and apparent efficiency of 7.5 kg polymer/g ZHCC (∼24.0 kg polymer/g Zn) were achieved at 3.8 MPa and 100 °C. The poly(cyclohexenylene carbonate) (PCHC) polymers obtained were completely atactic with a molecular weight (Mn) of ∼10 kg/mol and polydispersity of 2.0–3.0. The PCHCs had a structure of nearly alternating CHO and CO2 units, with a molar fraction of carbonate units of 0.44–0.47. Preliminary investigations of the mechanism suggest that nucleophilic attack by neighboring oxygen atoms is involved in copolymerization initiation with ZnCoIII DMCCs.