Constructing Photocatalytic Covalent Organic Frameworks with Aliphatic Linkers

Area of Science:

• Materials Science
• Photocatalysis
• Organic Chemistry

Background:

• Conventional photocatalytic covalent organic frameworks (COFs) utilize rigid aromatic linkers, leading to hydrophobicity that hinders performance in aqueous environments.
• Developing water-compatible photocatalysts is crucial for efficient solar fuel production and environmental remediation.

Purpose of the Study:

• To synthesize novel hydrophilic COFs using aliphatic linkers for enhanced water-based photocatalysis.
• To investigate the photocatalytic activity of these new COFs for hydrogen peroxide (H₂O₂) and hydrogen (H₂) evolution.

Main Methods:

• Synthesis of hydrophilic COFs using tartaric acid dihydrazide (TAH) and butanedioic acid dihydrazide as aliphatic linkers.
• Characterization of COF structure, crystallinity, hydrophilicity, and optical properties (band gap).
• Evaluation of photocatalytic performance for H₂O₂ and H₂ evolution under visible light, including theoretical calculations.

Main Results:

• Successfully synthesized hydrophilic COFs with aliphatic linkers exhibiting enhanced crystallinity and water compatibility.
• Aliphatic linker COFs displayed strong visible light absorption (band gap ~1.9 eV) and unusual ABC stacking with ~0.6 nm nanopores.
• TAH-COF achieved a record H₂O₂ evolution rate of 6003 μmol h⁻¹ g⁻¹ without sacrificial agents.
• Theoretical calculations confirmed TAH linker's role in enhancing the oxygen reduction reaction for H₂O₂ production.

Conclusions:

• Hydrophilic COFs constructed with aliphatic linkers offer a promising alternative to hydrophobic aromatic COFs for water-based photocatalysis.
• This study introduces a new strategy for designing advanced semiconducting COFs using nonaromatic building blocks.
• The developed TAH-COF demonstrates superior performance for H₂O₂ evolution, opening new avenues in photocatalysis research.