# Regulation of Excitonic Behavior in Defective Acetylenic Polymers Enables Mechanism Switching in O2 Activation for Enhanced Water Decontamination

## TL;DR

This paper explores how defects in a specific polymer can control how oxygen is activated, leading to better water decontamination.

## Contribution

The study introduces a novel method to switch oxygen activation mechanisms using molecular defects in polymers.

## Key findings

- Defects in PTEB regulate exciton behavior and enable mechanism switching in O2 activation.
- Artificial internal electric fields direct charge carrier migration, enhancing superoxide radical generation.
- The strategy improves contaminant removal efficiency through selective ROS generation.

## Abstract

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 (Eb) 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.

A molecular defect‐mediated charge accumulation strategy is developed to regulate the exciton behavior for selective molecular oxygen (O2)activation in poly(1,3,5‐triethynylbenzene) (PTEB). Artificial internal electric field (IEF) constructed in defective PTEB provides internal driving force to steer the directed migration of charge carriers, thereby switching the O2 activation from traditional energy transfer (primarily yielding singlet oxygen (1O2)) to a hot charge‐driven pathway (primarily yielding superoxide radical (O2
•−)).