Regioisomeric Control of Planarity Enhances Exciton Dissociation in Conjugated Polymer for High-Efficiency Photocatalytic H2 Evolution

Abstract

Organic conjugated polymers (CPs) are promising photocatalysts for solar-to-hydrogen conversion, yet their efficiency is often limited by large exciton binding energies and poor charge separation. In this study, we report a molecular isomerization strategy to control polymer planarity and thereby enhance exciton dissociation and photocatalytic activity. Two isomeric CPs, Pyrene-Thiophene-Benzothiazole (Py-T-BT) and Pyrene-Thiophene-iso-Benzothiazole (Py-T-isoBT), were designed and synthesized, employing pyrene as the donor, thiophene as the π-bridge, and either benzothiadiazole (BT) or its structural isomer (isoBT) as the acceptor. The introduction of the isoBT unit induced steric hindrance, resulting in Py-T-isoBT exhibiting significantly reduced molecular planarity (dihedral angles of 30.3° and 9.2°) compared to the highly planar Py-T-BT (dihedral angle of 4.2°). Theoretical calculations and experimental characterizations confirmed that the more planar Py-T-BT possessed a narrower band gap, a larger transition dipole moment, and consequently a lower exciton binding energy. Time-resolved spectroscopy revealed that Py-T-BT enabled ultrafast formation of charge transfer excitons (τCT = 0.60 ps), in contrast to Py-T-isoBT (τCT = 3.95 ps). As a result, Py-T-BT demonstrated a photocatalytic hydrogen evolution rate of 7.61 mmol·g⁻¹·h⁻¹ with 3 wt% Pt cocatalyst under visible light irradiation (λ ≥ 420 nm), approximately 20 times higher than Py-T-isoBT. This work highlights the pivotal role of molecular planarity in modulating exciton dynamics and presents a generalizable strategy for designing high-efficiency polymer photocatalysts through isomeric engineering.

Supplementary files

Article information

Article type
Paper
Submitted
22 May 2025
Accepted
19 Aug 2025
First published
22 Aug 2025

J. Mater. Chem. A, 2025, Accepted Manuscript

Regioisomeric Control of Planarity Enhances Exciton Dissociation in Conjugated Polymer for High-Efficiency Photocatalytic H2 Evolution

Y. Zhuang, W. Li, Q. Yang, H. Li, H. Huang, X. Huang and J. Long, J. Mater. Chem. A, 2025, Accepted Manuscript , DOI: 10.1039/D5TA04143K

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements