Dual‐Polarized Donor–Acceptor Polymer Unlocks Long‐Lived Triplet Excitons for High‐Efficiency H 2 O 2 Photosynthesis

ABSTRACT Long‐lived triplet excitons in polymers are crucial for driving oxygen reduction reaction (ORR) in photocatalytic H 2 O 2 production, but their formation is typically limited by weak spin‐orbit coupling (SOC) and a large singlet–triplet splitting energy (Δ E ST ). Here we present a “dual‐polarized” strategy in a novel donor–acceptor (D–A) polymer (MQDP) containing S═N─C and C═N─C linkages. MQDP polymer was prepared via supramolecular precursor polymerization of acenaphthenequinone (AQ), dibenzothiophene‐5‐oxide (DPO), and melem (ME). Compared to the single‐polarized analogue MQP ( τ p = 672 µs), the dual‐polarized units in MQDP enhance SOC and reduce Δ E ST , thereby generating multiple singlet‐to‐triplet intersystem crossing (ISC) transfer channels to produce long‐lived triplet excitons ( τ p = 868 µs). In addition, the dual‐polarized MQDP enriches surface−active sites for O 2 adsorption, effectively reducing the energy barrier for ORR. The MQDP achieves a remarkable H 2 O 2 generation rate of 15.38 mmol g −1 h −1 under visible light irradiation and ambient air, nearly 1.9 times higher than that of MQP (8.13 mmol g −1 h −1 ). These findings demonstrate the effectiveness of the dual‐polarized design in tuning exciton dynamics and surface reactivity of D–A polymers for enhanced photocatalysis.