# In-situ formatting donor-acceptor polymer with giant dipole moment and ultrafast exciton separation

## TL;DR

This paper introduces a new post-synthetic method to create donor-acceptor polymers with enhanced photocatalytic properties for hydrogen peroxide synthesis.

## Contribution

A light-induced post-synthetic method to convert polymers into donor-acceptor states with efficient exciton separation.

## Key findings

- The polymer exhibits a large intramolecular dipole moment and efficient exciton separation.
- The method enhances photocatalytic hydrogen peroxide synthesis.
- Time-resolved techniques confirm transient exciton behavior and charge transfer states.

## Abstract

Donor-acceptor semiconducting polymers present countless opportunities for application in photocatalysis. Previous studies have showcased their advantages through direct bottom-up methods. Unfortunately, these approaches often involve harsh reaction conditions, overlooking the impact of uncontrolled polymerization degrees on photocatalysis. Besides, the mechanism behind the separation of electron-hole pairs (excitons) in donor-acceptor polymers remains elusive. This study presents a post-synthetic method involving the light-induced transformation of the building blocks of hyper-cross-linked polymers from donor-carbon-donor to donor-carbon-acceptor states, resulting in a polymer with a substantial intramolecular dipole moment. Thus, excitons are efficiently separated in the transformed polymer. The utility of this strategy is exemplified by the enhanced photocatalytic hydrogen peroxide synthesis. Encouragingly, our observations reveal the formation of intramolecular charge transfer states using time-resolved techniques, confirming transient exciton behavior involving separation and relaxation. This light-induced method not only guides the development of highly efficient donor-acceptor polymer photocatalysts but also applies to various fields, including organic solar cells, light-emitting diodes, and sensors.

Donor-acceptor polymers have potential for application in photocatalysis, but often harsh synthetic conditions are required. Here, the authors report a post-synthetic method for conversion to donor-acceptor states, to give a polymer capable of enhancing photocatalytic hydrogen peroxide synthesis.