Understanding low-pressure CO₂ insertion chemistry in epoxide-CO₂ copolymerization catalysis

Despite many CO₂ use strategies being reliant on fast and selective CO₂ insertion reactions into metal-alkoxide bonds, in-depth studies into this chemistry remain rare. Here the effect of CO₂ pressure on the CO₂ insertion chemistry is studied using epoxide-CO₂ copolymerizations. Five high-performance literature catalysts are investigated under systematically varied CO₂ pressures, revealing kinetic profiles indicative of CO₂ insertion equilibria. For each catalyst, two key parameters describing the CO₂ insertion chemistry are determined: the equilibrium constant, K_eq, and the saturation CO₂ pressure above which catalytic performance is maximized, P_threshold. Generalizable correlations between copolymerization activity, K_eq and P_threshold are uncovered and used to predict performances for four further catalyst-monomer combinations. These correlations are a direct link between CO₂ insertion chemistry and process operating conditions, providing a mechanistic framework and testing protocols to accelerate future catalyst development. These results should help deliver efficient scalable CO₂ use technologies, operating with minimal energy.