Continuous π-Conjugation in β-Ketoenamine Covalent Organic Frameworks Boosts Charge Transfer for Selective...

Area of Science:

• Materials Science
• Photocatalysis
• Organic Chemistry

Background:

• Covalent organic frameworks (COFs) with alkynyl groups in their backbones facilitate continuous π-conjugation.
• This π-conjugation is crucial for enhancing visible light photocatalysis.
• Previous COFs lacked sufficient π-electron delocalization for optimal performance.

Purpose of the Study:

• To synthesize and characterize new β-ketoenamine COFs with varying degrees of π-conjugation.
• To investigate the impact of continuous π-conjugation on optoelectronic properties and photocatalytic activity.
• To explore the mechanism of visible light-driven selective amine oxidation using these novel COFs.

Main Methods:

• Synthesis of TpEDD-COF and TpBDD-COF by incorporating acetylene and diacetylene linkers into TpBD-COF.
• Density Functional Theory (DFT) calculations to assess π-electron delocalization and planarity.
• Experimental measurements of optoelectronic properties and photocatalytic activity under visible light irradiation (460 nm).
• Mechanistic studies to identify reactive oxygen species.

Main Results:

• TpEDD-COF and TpBDD-COF exhibit greater planarity and amplified π-electron delocalization compared to TpBD-COF.
• Optoelectronic properties follow the order: TpBDD-COF > TpEDD-COF > TpBD-COF.
• TpBDD-COF demonstrated four times the catalytic conversion of TpBD-COF in selective benzylamine oxidation.
• Superoxide radical anion was identified as the key reactive species in TpBDD-COF photocatalysis.

Conclusions:

• Continuous π-conjugation in COFs is a key factor for enhancing visible light photocatalysis.
• The synthesized TpEDD-COF and TpBDD-COF show superior performance in selective amine oxidation.
• This study provides a viable strategy for designing advanced COFs for efficient photocatalytic applications.