Metal-free synthesis of poly(trimethylene carbonate) by efficient valorization of carbon dioxide

The desire for sustainability drives interest in the production of chemicals from carbon dioxide. The synthesis of poly(trimethylene carbonate), PTMC, by copolymerization of carbon dioxide and oxetane using organocatalysis affords a green route to this important polymer but has proven to be a very challenging process. Herein we report that the application of iodine, in combination with organic superbases provides a highly active system for the direct synthesis of PTMC from CO₂ with very high levels of carbonate linkage (95% in selectivity). Mechanistic studies reveal the in situ formation of trimethylene carbonate which eventually polymerizes through an active chain-end process from an I₂-oxetane adduct.