Bio‐Inspired Polymer Nanoreactor: Integrating Hemin Coordination and Micellar Confinement for Catalysis in Water

Harnessing the catalytic power of heme catalysts for advanced synthesis, particularly in environmentally benign aqueous media, remains a significant challenge due to hemin's poor solubility and the need for precise microenvironment control. Here, the study reports a tailored amphiphilic random‐block copolymer, poly(histidine‐random‐styrene)‐block‐poly( N,N ‐dimethylacrylamide) (P(His‐r‐Sty)‐b‐PDMAA), designed as an “all‐in‐one” nanocarrier for efficient aqueous hemin catalysis. Synthesized via controlled RAFT polymerization, this copolymer self‐assembles into stable nanomicelles featuring a hydrophobic core functionalized with histidine residues for specific axial coordination of hemin, and a hydrophilic shell ensuring aqueous compatibility. This precisely engineered architecture enables the highly efficient cyclopropanation of styrene with ethyl diazoacetate in water using only 0.3 mol% hemin loading, achieving yields up to 94.4% under ambient air. The catalytic system demonstrates robustness and sustainability, retaining over 90% activity after four cycles via a simple extraction‐based recovery. Thus, the work showcases a powerful strategy integrating controlled polymer synthesis and bio‐inspired ligand design to create highly active and recyclable catalysts for challenging transformations in water.