A visible-light photoinduced controlled radical polymerization using recyclable MIL-100 (Fe) metal-organic frameworks

Controlled polymer techniques have significantly advanced thanks to using the energy of light to control radical polymerizations. Although many photocatalysts (e.g. metal catalysts, organocatalysts, semiconductor materials, etc.) have been reported, most of these catalysts are still expensive synthetic, trace oxygen-sensitive, and often use UV source light to create the activator to the polymerization. Metal-organic frameworks (MOFs), consisting of metal clusters coordinated to organic ligands, are rising stars as heterogeneous photocatalysis for living radical polymerization techniques because they have many advantages such as facile operation, low toxicity, air stability, and sustainability. Herein, we reported a robust and versatile Fe(III)-MOF, MIL-100(Fe), as a heterogeneous photocatalyst for controlled atom transfer radical polymerization (ATRP) under visible light and natural sunlight without any additives. Moreover, controlled polymerization was also achieved in the presence of oxygen. Many polymer compositions including homopolymers, random copolymers, and diblock copolymers were successfully prepared with well-defined molecular weights and narrow dispersity index values (D < 1.5). Most importantly, the heterogeneous Fe(III)-MOF catalyst was allowed easily separated and can be reused again for ATRP reaction for ten cycles that maintains the high photocatalytic efficiency. This method provides a new avenue for exploring MIL-100(Fe) as a low-cost, high-performance, and sustainable catalyst for photo-ATRP.