Nitrogen Modulation in Multipyrimidine- and Multipyridine-Based Covalent Organic Frameworks with Exceptional...

Area of Science:

• Photocatalysis
• Green Chemistry
• Materials Science

Background:

• Solar energy conversion for chemical synthesis is crucial.
• Hydrogen peroxide (H₂O₂) production from water and air using solar energy is a key research area.
• Covalent organic frameworks (COFs) offer tunable properties for photocatalysis.

Purpose of the Study:

• To synthesize novel nitrogen-rich COFs for enhanced photocatalytic H₂O₂ production.
• To investigate the impact of nitrogen atom configuration on COF photocatalytic efficiency.
• To understand the structure-property relationships and mechanism of H₂O₂ photosynthesis in these COFs.

Main Methods:

• Synthesis of three new triamino monomers and their polycondensation with 1,3,5-triformylphloroglucinol to form COFs.
• Photocatalytic evaluation of COFs for H₂O₂ production under visible light.
• Characterization of COFs and mechanistic studies using controlled experiments and theoretical calculations.

Main Results:

• Three COFs with high specific surface areas were successfully synthesized.
• The benzene-cored multipyrimidine COF achieved record H₂O₂ production rates (10762 µmol g⁻¹ h⁻¹ in water/O₂ and 9613 µmol g⁻¹ h⁻¹ in water/air) without sacrificial agents.
• Photocatalytic efficiency was significantly enhanced by optimizing nitrogen atom positions in the COF building blocks.

Conclusions:

• Molecular engineering of nitrogen-rich COFs is a promising strategy for highly efficient H₂O₂ photosynthesis.
• The developed COFs represent state-of-the-art photocatalysts for green H₂O₂ production.
• This work provides fundamental insights into designing advanced COFs for solar fuel applications.