Department of Chemistry

Department of Chemistry University of Oxford

Exploiting Heterodinuclear Synergy to Prepare Better Catalysts for Carbon Dioxide Utilization

Exploiting Heterodinuclear Synergy to Prepare Better Catalysts for Carbon Dioxide Utilization

A paper by the Williams Research Group, published and highlighted (in news and views) in Nature Chemistry, provides new insight into intermetallic synergy in catalysts for the copolymerization of carbon dioxide and epoxides. Carbon dioxide copolymerization is an industrially-relevant means to valorise waste gases and improve sustainability in polymer manufacturing. The products, aliphatic polycarbonates, are used to make polyurethanes or plastic films - both products could be useful to add value to carbon capture and storage technologies. The efficiency of any carbon dioxide and epoxide copolymerization process depends on the choice of the polymerization catalyst, and the research highlights a new catalyst design strategy. Specifically, a heterodinuclear catalyst, with both Mg(II) and Co(II) coordinated by a macrocyclic ligand, shows some of the highest reported activities in carbon dioxide copolymerization and operates efficiently under low (atmospheric) carbon dioxide pressures. The heterodinuclear Mg(II)Co(II) catalyst shows enhanced performance compared to either of the homodinuclear analogues (Mg(II)Mg(II) and Co(II)Co(II) complexes) or to mixtures of them; this finding suggests synergy between the Mg(II) and Co(II) metal centres. The article investigates the intramolecular synergy using polymerization kinetics experiments and reveals that the Mg(II) centre reduces the transition state entropy whilst the Co(II) reduces the transition state enthalpy compared to homodinuclear catalysts. The better catalyst performances arise from this intramolecular synergy between the two metals, which adopt distinct roles and mediate each other's reactivity during catalysis. more........