Correlating Metal Redox Potentials to Co(III)K(I) Catalyst Performances in Carbon Dioxide and Propene Oxide Ring Opening Copolymerization

Carbon dioxide copolymerization is a front-runner CO2 utilization strategy but its viability depends on improving the catalysis. So far, catalyst structure-performance correlations have not been straightforward, limiting the ability to predict how to improve both catalytic activity and selectivity. Here, a simple measure of a catalyst ground-state parameter, metal reduction potential, directly correlates with both polymerization activity and selectivity. It is applied to compare performances of 6 new heterodinuclear Co(III)K(I) catalysts for propene oxide (PO)/CO2 ring opening copolymerization (ROCOP) producing poly(propene carbonate) (PPC). The best catalyst shows an excellent turnover frequency of 389 h(-1) and high PPC selectivity of >99 % (50 & DEG;C, 20 bar, 0.025 mol% catalyst). As demonstration of its utility, neither DFT calculations nor ligand Hammett parameter analyses are viable predictors. It is proposed that the cobalt redox potential informs upon the active site electron density with a more electron rich cobalt centre showing better performances. The method may be widely applicable and is recommended to guide future catalyst discovery for other (co)polymerizations and carbon dioxide utilizations.

Automated summary

Carbon dioxide copolymerization is a promising strategy for CO2 utilization, but the success depends on improving the catalysis. However, the relationship between catalyst structure and performance is not straightforward, which limits the ability to predict and enhance both catalytic activity and selectivity. In this study, a simple measure of a catalyst ground-state parameter, metal reduction potential, is shown to directly correlate with both polymerization activity and selectivity. This method has been successfully applied to compare the performance of 6 new heterodinuclear Co(III)K(I) catalysts for CO2 copolymerization, providing valuable insights for future catalyst discovery.