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[CTF-TCB] A General Strategy for Kilogram-Scale Preparation of Highly Crystalline Covalent Triazine Frameworks
Summary:
The authors from Westlake University developed a series of highly crystalline covalent triazine frameworks (CTFs) with high specific surface areas, achieving remarkable results in the application of micropollutant removal and photocatalytic hydrogen evolution.
Background:
1. To address the challenge of scalable and eco-friendly synthesis of crystalline porous CTFs for industrial applications, previous researchers explored methods such as high-temperature ionothermal strategy, superacid-catalyzed strategy, amidine-based polycondensation methods, and P2O5-catalyzed method. These methods achieved certain success, yet they faced issues like metal residues, strong corrosiveness, complex synthesis processes, relatively low specific surface areas, or unclear catalytic mechanisms, limiting their wide applications.
2. The authors in this work proposed an innovative polyphosphoric acid (H6P4O13)-catalyzed nitrile trimerization route and obtained crystalline CTFs with high specific surface areas and well-defined porosity at the kilogram level for the first time.
Research Content:
1. Synthesis:
The authors synthesized the highly crystalline CTFs using the H6P4O13-catalyzed nitrile trimerization method from various aromatic nitrile monomers, including TCB, DCB, TCT, and DCBP.
2. Characterizations:
1) The BET surface areas of the crystalline CTFs were 794, 1501, 702, and 1335 m²g⁻¹ for CTF-TCB, CTF-DCB, CTF-TCT, and CTF-DCBP, respectively. The pore size distribution centered at 0.7 nm, 1.1 nm, 1.1 nm, and 2.0 nm.
2) SEM tests showed the layered stacking structure of the crystalline CTFs, and AFM images revealed the thickness of exfoliated nanosheets to be 2.5–3 nm.
3) FTIR, solid-state 13C NMR, and XPS analyses confirmed the efficient formation of triazine units. TGA demonstrated their excellent thermal stability without obvious weight loss up to 600°C under N₂ atmosphere.
3. Application:
The crystalline CTFs were tested for micropollutant removal, showing ultrahigh removal efficiency of antibiotics (e.g., ofloxacin) with a maximum adsorption capacity of 297 mgg⁻¹ and over 99.9% removal efficiency. In photocatalytic hydrogen evolution, the crystalline semiconducting CTFs synthesized at 300°C exhibited appreciable performance.
4. Mechanism:
The analysis of experimental results and density functional theory (DFT) calculations revealed that H6P4O13 had significantly lower activation energy for nitrile trimerization than P2O5 and H3PO4, contributing to its higher catalytic activity. The highly crystalline porous structure of CTFs facilitated guest molecule transport and enhanced adsorption performance.
Outlook:
This research achieved a scalable and eco-friendly synthesis of highly crystalline CTFs with high specific surface areas and excellent performance in micropollutant removal and photocatalysis, providing a new strategy for the rational and mass preparation of crystalline porous polymers to promote their industrial applications.
A General Strategy for Kilogram-Scale Preparation of Highly Crystalline Covalent Triazine Frameworks
Authors: Tian Sun, Yan Liang, Wenjia Luo, Lei Zhang, Xiaofeng Cao, Yuxi Xu
DOI: 10.1002/anie.202203327
Link: https://onlinelibrary.wiley.com/doi/10.1002/anie.202203327
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