Catalytic Polymerization of n‐Doped Poly(benzodifurandione) (n‐PBDF) Using Parts Per Million (ppm) Level of Molybdenum Trioxide

The recent discovery of highly conductive, solution‐processable, n‐doped poly(benzodifurandione) (n‐PBDF) has significantly pushed the boundaries of organic electronics. However, to maximize its practical impact, a scalable and cost‐effective synthetic method is essential. Initially, n‐PBDF was synthesized via duroquinone‐mediated or copper‐catalyzed polymerizations, but these methods required prolonged dialysis, limiting their scalability. Our recent SeO₂‐catalyzed polymerization improved efficiency but still necessitated centrifugation and filtration to remove solid selenium byproducts. In this work, we introduce a highly efficient molybdenum trioxide (MoO₃)‐catalyzed polymerization of n‐PBDF. Remarkably, MoO₃ at parts‐per‐million (ppm) concentrations achieves near‐quantitative monomer conversion (>99% by NMR), eliminating the need for purification. Kinetic studies demonstrate that this polymerization follows a chain‐growth mechanism, enabling the synthesis of high‐quality n‐PBDF polymers with controlled particle sizes and block copolymers. Mechanistic investigations reveal that MoO₃ mediates an oxidative pathway involving dimethyl sulfoxide (DMSO), with dimethyl sulfide (DMS) identified as the reduction product. This breakthrough not only provides a scalable, low‐cost route to high‐quality n‐PBDF but also unlocks new synthetic opportunities, significantly expanding the synthetic toolbox for functional polymers.