Robust porphyrin catalysts immobilized on biogenous iron oxide for the repetitive conversions of epoxides and CO₂ into cyclic carbonates

Metalloporphyrins were immobilized on biogenous iron oxide (BIO) produced by iron-oxidizing bacteria, Leptothrix ochracea. These organic-inorganic hybrid materials were used as immobilized catalysts for the synthesis of cyclic carbonates from epoxides and CO₂ under solvent-free conditions. Zn^II porphyrin immobilized via four tetraalkylammonium bromide groups showed high catalytic activity and reusability at a catalyst loading of 0.1 mol%. The product was obtained in 99% yield after nine times reuse, and the substrate scope was broad.