Insertion of CO2 to 2-methyl furoate promoted by a cobalt hypercrosslinked polymer catalyst to obtain a monomer of CO2-based biopolyesters†

2,5-Furan Dicarboxylic methyl Ester (FDME), a highly valued monomer for the synthesis of biobased polyesters, has been prepared through a new synthetic strategy that consists of the direct carboxylation of methyl furoate in two steps: the first one involves a solvent-free reaction using a moderate CO₂ pressure (10 bar), a base (Cs₂CO₃) and a cobalt-based heterogeneous catalyst (HCP-Salphen-Co) for 6 h, which was prepared using mechanochemical polymerization. The second step consists of an acid esterification using standard conditions. The CO₂-based FDME synthesized with this strategy was successfully reacted with a diol derived from vanillin, thus obtaining a CO₂ and a completely bio-based polyester which exhibited high thermal stability with a starting degradation temperature of 250 °C and a glass transition temperature of 104 °C.