Cobaltoporphyrin with heterocyclic wings promoted cycloaddition of epoxides and CO2

Five N -heterocyclic-modified cobaltoporphyrins were designed and synthesized as bifunctional homogeneous catalysts. They have demonstrated high efficiency in catalyzing the cycloaddition of epoxides and CO 2 to produce cyclic carbonates without a cocatalyst. The nucleophilicity of N -heterocyclic modification groups on metalloporphyrin ligands was found to directly impact their catalytic performance. Under the optimal conditions, catalyst J- o 4B exhibited the best catalytic performance with 99.9% PO conversion and >99% selectivity, while demonstrating notable substrate generality. A preliminary investigation into the kinetic behavior of the cycloaddition between epichlorohydrin (ECH) and CO 2 was carried out, employing three distinct N -heterocyclic-modified cobaltoporphyrins J- o 4B, J- o 4P and J- o 4T . The apparent activation energies of the cycloaddition reaction in the presence of various catalyst were subsequently determined. Moreover, the catalyst structure and experimental results were scrutinized to validate the proposed tri-synergistic catalytic mechanism for the cycloaddition of epoxides and CO 2 catalyzed by the N -heterocyclic-modified cobaltoporphyrins.