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[TpDAF-COF] Engineering fluorene-based COFs photocatalysts toward efficient and selective aerobic oxidation of amines
Summary:
The authors from Wuhan University developed fluorene-based covalent organic frameworks (COFs) with high crystallinity and porosity, achieving significant results in the selective aerobic oxidation of amines to imines.
Background:
1. To address the challenge of constructing crystalline materials like COFs using fluorenes, which have twisted structures that hinder crystallinity, previous researchers explored various methods but faced issues such as low crystallinity and porosity.
2. The authors in this work proposed an innovative method of engineering COFs with functional groups and obtained remarkable results in terms of crystallinity, porosity, and photocatalytic efficiency.
Research Content:
1. Synthesis:
The authors synthesized three fluorene-based COFs (TpDAF-COF, TpMFC-COF, and TpFFC-COF) using a solvothermal method with 1,3,5-triformylphloroglucinol (Tp) and different diamines (DAF, MFC, FFC) under uniform conditions.
2. Characterizations:
1) The BET specific surface areas were 1204, 820, and 1010 m²g⁻¹ for TpDAF-COF, TpMFC-COF, and TpFFC-COF, respectively. The pore size distribution was around 1.2 nm for all COFs.
2) SEM and TEM tests showed uniform micro-sized spherical morphology with particle sizes of approximately 1 µm.
3) Optoelectronic tests revealed that TpFFC-COF had the most intense photocurrent density and the lowest interfacial charge transfer resistance.
3. Application:
The COFs were tested for the selective aerobic oxidation of amines to imines. TpFFC-COF showed the highest conversion efficiency (92%) and selectivity (99%), followed by TpMFC-COF and TpDAF-COF.
4. Mechanism:
The analysis of experimental results and DFT calculations indicated that the introduction of fluoro groups improved charge separation and transfer efficiency. The fluoro group's strong electronegativity and small steric hindrance enhanced the photocatalytic performance.
Outlook:
This research provides crucial insights into the design and engineering of COF photocatalysts with functional groups, highlighting their potential for efficient and selective photocatalytic applications in organic synthesis.
Engineering fluorene-based covalent organic framework photocatalysts toward efficient and selective aerobic oxidation of amines
Authors: Kanghui Xiong, Keke Zhang, Fulin Zhang, Bing Zeng, Xianjun Lang
DOI: 10.1016/j.jcis.2024.11.105
Link: https://www.sciencedirect.com/science/article/pii/S0021979724007185
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