Boosting Built-in Electric Field via COF Molecular Quadrupole Gradients for Efficient H₂O₂ Photosynthesis

Area of Science:

• Materials Science
• Photocatalysis
• Green Chemistry

Background:

• Covalent organic frameworks (COFs) show potential for photocatalytic hydrogen peroxide (H2O2) generation.
• Intrinsic polarization (dipole moment) aids exciton dissociation but is limited in symmetric COFs.
• Lack of significant dipole moment in COFs hinders built-in electric field regulation for efficient photocatalysis.

Purpose of the Study:

• To engineer COFs by modulating quadrupole moments to enhance local electric fields.
• To improve the efficiency of H2O2 generation using COFs as photocatalysts.
• To investigate the relationship between quadrupole moments and photocatalytic performance.

Main Methods:

• Molecular engineering of specific COF sites to introduce quadrupole moments.
• Fabrication and characterization of modified COFs.
• Photocatalytic experiments for H2O2 generation using water, air, and light.
• In-situ studies of local electric fields and carrier dynamics.

Main Results:

• Achieved a high H2O2 photosynthesis rate of 8.32 mmol g-1 h-1 without sacrificial agents.
• Demonstrated that quadrupole moment gradients tune carrier decay, fluorescence reabsorption, and exciton binding energy.
• Showcased stabilization of the adsorbed 2-hydroperoxyl (·OOH) intermediate via polarization and electron redistribution.

Conclusions:

• Molecular engineering of quadrupole moments offers a strategy for manipulating local electric fields in COFs.
• Quadrupole moments significantly influence carrier utilization efficiency and photocatalytic activity.
• This approach provides fundamental insights into optimizing non-polar COF photocatalysts for H2O2 production.