Regulating Exciton Dynamics in Organic Polymer Photocatalysts with Dual-Polarization Structure

The generation of different reactive species during photocatalysis involves complex exciton transformation mechanisms that remain unclear, posing a key academic challenge in enhancing photocatalytic performance. This study focuses on a dual-polarized organic polymer, SBN, constructed via molecular engineering strategies, to explore its exciton dynamics and their impact on photocatalytic performance. Theoretical calculations show that the introduction of B–N Lewis pairs and cyano groups in the SBN significantly reduces the energy splitting between the lowest excited spin-singlet (S₁) state and the lowest excited spin-triplet (T₁) state (∆E_ST), which enhances the efficiency of intersystem crossing (ISC) and reverse intersystem crossing (RISC). Spectroscopic analysis further reveals the rapid and reversible ISC and RISC processes of excitons in SBN across different temperatures and time scales. Moreover, the lifetime of excitons is extended, providing more abundant time for electron and energy transfer in photocatalytic reactions. These findings demonstrate that the optimized exciton dynamics in SBN provide strong support for efficient photocatalysis. In various photocatalytic experiments, including water splitting for hydrogen production, thioether oxidation, and H₂O₂ synthesis, SBN exhibits significantly better performance than the control polymer TCC.