Dual-Polarized Donor-Acceptor Polymer Unlocks Long-Lived Triplet Excitons for High-Efficiency H₂O₂ Photosynthesis

Long-lived triplet excitons in polymers are crucial for driving oxygen reduction reaction (ORR) in photocatalytic H₂O₂ production, but their formation is typically limited by weak spin-orbit coupling (SOC) and a large singlet-triplet splitting energy (ΔE_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 ΔE_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 O₂ adsorption, effectively reducing the energy barrier for ORR. The MQDP achieves a remarkable H₂O₂ 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.