Pyrimidine donor induced built-in electric field between melon chains in crystalline carbon nitride to facilitate excitons dissociation

The strong intrinsic Coulomb interactions of Frenkel excitons in crystalline carbon nitride (CCN) greatly limits their dissociation into electrons and holes, resulting in unsatisfactory charges separation and pho-tocatalytic efficiency. Herein, we propose a strategy to facilitate excitons dissociation by molecular regula-tion induced built-in electric field (BIEF). The electron-rich pyrimidine-ring into CCN changes the charge density distribution over heptazine-rings to induce BIEF between melon chains. Such BIEF is sufficient to overcome the considerable exciton binding energy (EBE) and reduce it from 38.4 meV to 16.4 meV, increasing the excitons dissociation efficiency (EDE) from 21.5% to 51.9%. Our results establish a strategy to facilitate excitons dissociation through molecular regulation induced BIEF, targeting the intrinsic high EBE and low EDE of polymer photocatalysts.(c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

The strong Coulomb interactions in crystalline carbon nitride hinder the dissociation of Frenkel excitons, leading to inefficient charge separation and photocatalytic efficiency. To address this issue, a strategy is proposed to induce a built-in electric field (BIEF) through molecular regulation. By changing the charge density distribution, the BIEF overcomes the high exciton binding energy (EBE) and significantly improves the exciton dissociation efficiency (EDE) from 21.5% to 51.9%. This study establishes a method to enhance exciton dissociation in polymer photocatalysts by molecular regulation-induced BIEF.