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

Understanding the microenvironment structure-activity relationship of photo-responsive polymers is crucial to steer the charge carrier flow for molecular oxygen (O₂) activation. However, the spin-forbidden nature of O₂ and the inherent Frenkel exciton effect hinder the efficient O₂ 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-NH₂, 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 O₂ 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 ─NH₂ defect, while ─CN defect is primary occupied with photo-induced hole (h⁺). The polarized distribution of charge carriers in PTEB-NH₂ endows the polymeric semiconductor with enhanced selectivity for superoxide radical (O₂ ^•-) generation and improved contaminant removal efficiency. This work offers promising prospective for regulating exciton behavior for organic polymers and opens a frontier for O₂ activation.