Accelerated Exciton Dissociation and Charge Transfer via Third‐Motif Engineered Conjugated Polymers for Photocatalytic Circulation‐flow Synthesis of H 2 O 2

Abstract Achieving effective exciton dissociation and charge transport in linear polymer photocatalysts for H 2 O 2 photosynthesis remains a formidable challenge. Herein, we fabricated three‐motif cross‐linked polymers by rationally introducing a third functional component into a two‐motif linear polymer, which were employed for circulation‐flow photocatalytic H 2 O 2 production. By strategically modulating the third component, we precisely tuned the electronic structure, significantly lowering exciton binding energy and enlarging the molecular dipole moment. Compared to the original linear configuration, the resulting cross‐linked structure creates multidirectional electron transport channels. Combined experimental and calculation investigations demonstrate that these synergistic effects collectively promote exciton dissociation and intramolecular electron transfer. PAQ‐TABPB photocatalyst with optimized third‐motif accelerates oxygen‐to‐superoxide radical transformation by lowering the *OOH binding energy, thereby facilitating the two‐step single‐electron oxygen reduction pathway, attaining an exceptional H 2 O 2 production rate of 3351 µmol g −1 h −1 . Notably, we constructed a circulation‐flow reactor for the photocatalytic synthesis of H 2 O 2 . Benefiting from improved gas‐liquid mass transfer and efficient light irradiation, this high‐speed flow system achieved a 5.2‐fold increase in H 2 O 2 production compared to a conventional batch reactor under the light intensity of 27 mW cm −2 , reaching an accumulated yield of 3125 µmol g −1 with stable recyclability. This work highlights the potential of multi‐component polymeric photocatalysts and circulation‐flow reactors for H 2 O 2 photosynthesis.