Formation of bio-based cyclic carbonates from CO2 and renewable feedstocks via porous poly(azomethine) -based heterogeneous catalysts approach

Two families of heterogeneous porous catalysts based on iron or cobalt poly(azomethine) (PAM) networks were reported to synthesize cyclic carbonates from bio-based aliphatic oxides epoxides and carbon dioxide (CO₂). The different PAM supports were prepared by reacting 2,6-pyridine dicarboxaldehyde with 1,3,5 tris(4 aminophenyl)benzene (PAM-1) or with melamine (PAM-2) by microwave activation. Both supports exhibited high thermal stability and similar CO₂ uptake (1.3 mmol/g) but PAM-2 showed higher specific surface area (779 m²/g vs 401 m²/g), more crystallinity and less capacity for anchoring metals than PAM-1. The novel catalysts were used in the cycloaddition of CO₂ to renewable feedstocks. Thus, using epoxidized methyl oleate (MOE) the corresponding cyclic carbonates were obtained with excellent yields (78–96 %) using a CO₂ pressure of 7 bars, 120 ºC and 16 h of reaction. The best catalysts of the series, Fe@PAMs were also evaluated in the cycloaddition of CO₂ to epoxidized soybean oil (ESBO) in the same condition reaction obtaining excellent performance, epoxide conversions and cyclic carbonate yields greater than 90 %.