Regulation of Excitonic Behavior in Defective Acetylenic Polymers Enables Mechanism Switching in O ₂ Activation for Enhanced Water Decontamination

Abstract Understanding the microenvironment structure−activity relationship of photo‐responsive polymers is crucial to steer the charge carrier flow for molecular oxygen (O ₂ ) activation. However, the spin‐forbidden nature of O ₂ and the inherent Frenkel exciton effect hinder the efficient O ₂ activation, particularly in achieving selective reactive oxygen species (ROSs) generation. Herein, the Sabatier volcano plot is first utilized to manipulate the microenvironment of poly(1,3,5‐triethynylbenzene) (PTEB) via molecular defect‐mediated charge accumulation to regulate the exciton behavior. The screened PTEB‐CN and PTEB‐NH ₂ , with thermodynamic advantages, are created artificial internal electric field (IEF) to induce exciton dissociation and oriented migration. Meanwhile, the significant weakening of exciton binding energy (E _b ) in defective PTEBs overcomes the Frenkel exciton effect, switching the O ₂ activation from a traditional energy transfer‐mediated nonradical route (pristine PTEB) to a hot charge‐driven radical pathway. Mechanism inquiry reveals the reversely oriented IEF dictates the migration direction of charge carriers, leading to predominant migration of photo‐induced electron (e ⁻ ) in conjugated sites toward the ─NH ₂ defect, while ─CN defect is primary occupied with photo‐induced hole (h ⁺ ). The polarized distribution of charge carriers in PTEB‐NH ₂ endows the polymeric semiconductor with enhanced selectivity for superoxide radical (O ₂ ^•− ) generation and improved contaminant removal efficiency. This work offers promising prospective for regulating exciton behavior for organic polymers and opens a frontier for O ₂ activation.