Recyclable Heterogeneous Photocatalysts Using Linear Conjugated Polymers for Red‐Light‐Driven Photo‐ <scp>ATRP</scp>

ABSTRACT We demonstrate that the commercially available linear conjugated polymer PffBT4T‐2OD, widely used in organic photovoltaics, can be directly repurposed as a heterogeneous photocatalyst for Cu‐mediated atom transfer radical polymerization (photo‐ATRP) under deep red light (690 nm). In combination with CuBr 2 /Me 6 TREN, this dual catalytic system mediates well‐controlled polymerization of a range of acrylate and methacrylate monomers, affording polymers with narrow molecular‐weight distributions ( Đ down to 1.07 at 1000 ppm CuBr 2 ), even under ultralow copper loading conditions ( Đ ≈1.16 at 25 ppm CuBr 2 ). The heterogeneous polymer photocatalyst can be readily recovered and reused for at least five cycles without appreciable loss of activity, and the system shows significant tolerance toward dissolved oxygen, enabling polymerization without rigorous deoxygenation. Electrochemical, spectroscopic, and EPR studies indicate that photoexcited PffBT4T‐2OD reduces Cu II to Cu I both directly and through an amine‐mediated pathway, consistent with a conventional photo‐ATRP activation–deactivation mechanism. This work introduces a simple, deep‐red‐responsive, and recyclable OPV‐based photocatalyst to the existing photo‐ATRP toolkit, providing a practical option for metal‐efficient polymer synthesis.