Accelerated Exciton Dissociation and Charge Transfer via Third‐Motif Engineered Conjugated Polymers for Photocatalytic Circulation‐flow Synthesis of H2O2

Achieving effective exciton dissociation and charge transport in linear polymer photocatalysts for H2O2 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 H2O2 production. By strategically modulating the third component, we precisely tuned the electronic structure, significantly lowering exciton binding energy and enlarging 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 H2O2 production rate of 3351 μmol/g/h. Notably, we constructed a circulation‐flow reactor for photocatalytic synthesis of H2O2. Benefiting from improved gas‐liquid mass transfer and efficient light irradiation, this flow‐system achieved a 5.2‐fold increase in H2O2 production compared to conventional batch reactor under the light intensity of 27 mW cm‐2, reaching an accumulated yield of 3125 μmol/g with stable recyclability. This work highlights the potential of multi‐component polymeric photocatalysts and circulation‐flow reactors for H2O2 photosynthesis.