Metal Polyphenol Network Enables Photo‐ATRP Under Blue Light

Photo‐ATRP commonly relies on petrochemical‐derived ligands and copper‐based catalytic systems, which is misaligned with green‐chemistry principles. Here, 4‐hydroxychalcone is used as a building block and functionalized amino groups through a Mannich reaction, then self‐assembled with FeBr 3 to form a metal‐polyphenol network (MPN). Under 420 nm visible‐light irradiation, the MPN effectively mediates photo‐ATRP, reaching a maximum monomer conversion of 67.4%. The resulting polymers exhibit a dispersity of Đ < 1.5, with values down to 1.3, indicating a certain control of polymerization. Using the PMMA ‐Br macroinitiator, synthesis of block copolymers comprising methyl methacrylate ( MMA ), benzyl methacrylate ( BMA ), and styrene ( St ) successfully succeeded. Notably, polymers exhibiting a dispersity of Đ < 1.5 were obtained even without degassing, while chain‐end fidelity was available. In addition, a FeCl 3 ‐catalyzed photo‐ATRP system is demonstrated. Overall, this work provides an operationally simple approach to light‐controlled radical polymerization using Fe catalysts with bio‐based ligands.