Kinetics and mechanism of the ring-opening copolymerization of CO2 and propylene oxide on a two-dimensional Co-Ni double metal cyanide complex

The use of CO 2 as building block in organic chemistry is compelling due to its availability, cost-effectiveness, and potential to mitigate emissions while generating valuable, sustainable materials. Ring-opening copolymerization (ROCOP) of CO 2 and epoxides is a prime example of this. The viability of this technology, however, is highly dependent on the performance of the catalyst, and the Co-Ni DMC complex has recently demonstrated significant potential for industrial application. Thus, this article delves into the physicochemical characterization of this complex and offers a detailed examination of the kinetics and mechanism of CO 2 /PO ROCOP using in situ infrared spectroscopy. The behaviour of the catalyst is investigated under various operating conditions, including four different reaction temperatures, yielding an apparent activation energy of 59.8 kJ/mol. Zero-order kinetics with respect to CO 2 pressure and first-order kinetics with respect to PO concentration are observed, with minimal formation of cyclic by-products across all conditions. The influence of chloride ions and the role of chain-transfer agents on the complex are corroborated. Based on the characterization, kinetic, and mechanistic studies, a coordinative cationic copolymerization mechanism is proposed for the studied complex. • Co-Ni DMC for efficient CO 2 /PO ROCOP with no induction period and no PC formation • First-order kinetics with respect to PO and zero-order with respect to CO 2 • Thermodynamic analysis reveals moderate activation energy (59.8 kJ/mol) • Proposed insertion-coordination mechanism with PO ring-opening by OH - or TBA groups • Chain transfer studies confirm catalysts potential for immortal polymerization