The Silk Route to Green Catalysis: Silk Fibroin as a Recyclable Ligand for Iron-Catalyzed Olefin Epoxidation

A sustainable, efficient, and cost-effective iron-catalyzed olefin epoxidation is achieved by coordinating iron ions with silk fibroin (SF), a biocompatible protein derived from Bombyx mori cocoons. Unlike conventional systems based on complex ligands or synthetic supports, SF acts both as a support and as a recyclable ligand, efficiently coordinating iron through a simple aqueous process. The resulting SF-coordinated Iron system [Fe(SF)] promotes epoxidation of a broad range of olefins under mild conditions, with excellent yields and low metal loading. Notably, the system combines high activity with remarkable recyclability, and it can be easily regenerated. This work introduces a green, scalable strategy for iron catalysis, demonstrating the untapped potential of a natural polymer as a renewable ligand in heterogeneous catalysis.