Engineering Photo-Controlled Dynamic Conjugation Switching in Azine-Linked Covalent Organic Frameworks for Boosted...

Area of Science:

• Materials Science
• Photocatalysis
• Organic Chemistry

Background:

• Photocatalysis offers solutions for energy and environmental issues.
• Covalent organic frameworks (COFs) show promise but suffer from electron-hole recombination.
• Optimizing COF structure is key to enhancing photocatalytic efficiency.

Purpose of the Study:

• To develop a dynamic conjugation-switching strategy for azine-linked COFs.
• To suppress electron-hole recombination in COFs.
• To enhance photocatalytic efficiency for applications like hydrogen peroxide production.

Main Methods:

• Synthesized three azine-based COFs (COF-TPTA, COF-TPB, COF-TPA) with varying electronic properties.
• Employed ultrafast spectroscopy and theoretical calculations to analyze electronic structures and charge carrier dynamics.
• Evaluated photocatalytic performance by measuring hydrogen peroxide production rates from oxygen and water.

Main Results:

• COF-TPB exhibited state-dependent conjugation, localizing π-electrons in the ground state and delocalizing them in the excited state.
• This dynamic conjugation in COF-TPB suppressed carrier recombination, leading to a H₂O₂ production rate of 1205 µmol g⁻¹ h⁻¹.
• The developed strategy was generalizable, achieving a high photocatalyst rate of 1463 µmol g⁻¹ h⁻¹ in other azine-based systems.

Conclusions:

• Dynamic electronic-structure engineering via conjugation switching is an effective strategy for optimizing COFs.
• COF-TPB demonstrates superior photocatalytic performance due to suppressed electron-hole recombination.
• This work provides a new paradigm for designing efficient photocatalysts.