Impact of Molecular Structure on Reactive Oxygen Species Generation in D–A Heterojunction Photocatalysts for Efficient Dye Degradation under Weak Light

Abstract The dual challenges of photocatalysis technology in addressing wastewater pollution and the energy crisis demand advanced photocatalysts with enhanced visible light absorption and efficient charge separation. This work utilizes bulk‐heterojunction organic solar cell (BHJ‐OSCs) active layers as photocatalytic sources, presenting PM6:PIID‐ClBF@BC, a biochar‐supported donor‐acceptor (D‐A) heterojunction organic photocatalyst, designed for water phototreatment and clarify the impacts of molecular structure on photocatalytic activity, simultaneously assist with challenges associated with OSCs waste disposal and resource secondary expansion. PM6:PIID‐ClBF@BC achieves complete RhB degradation within 10 minutes and maintains nearly 100% over 20 cycles. Additionally, it generated 28.15 µmol of H₂ within 3 hours, corresponding to a rate of 187.67 µmol h⁻¹ g⁻¹. The superior performance is attributed to its broader visible‐light absorption, increased electronegativity (enhanced dipole moment) induced by chlorine substitution, and favorable stacking interactions provide larger electron delocalization, forming a strong internal electric field that drives efficient charge separation and intramolecular charge transfer thereby enhancing reactive oxygen species generation. Electrostatic interactions between PM6:PIID‐ClBF@BC and RhB facilitate effective adsorption and catalysis, with higher superoxide radical levels driving degradation. This highlights the crucial role of molecular structure in optimizing photocatalytic performance, offering insights for designing next‐generation photocatalysts for environmental remediation and sustainable energy.