Covalent Triazine Frameworks

Covalent triazine frameworks (CTFs) represent the bridge between carbon nitride materials and conjugated organic polymers, combining the thermally stable and strong triazine motifs from PTI-type carbon nitrides with variable rigid aromatics. The joints are combined to extend the π conjugation and function in the conjugated polymer.

However, unlike carbon nitride, CTFs are essentially microporous and mesoporous 2D polymers, and therefore, are more similar to a wider range of π-conjugated porous polymers and covalent organic frameworks, depending on their structural order.

As a class of organic framework materials, CTFs have unique porosity and high nitrogen content. Most CTFs are amorphous or semi-crystalline.

Alfa Chemistry Catalysts can provide customers with CTFs catalysts and common raw materials used to synthesize CTFs, and provide you with catalyst solutions.

Preparation Methods for CTFs

• Ion thermal method

Covalent triazine frameworks can be synthesized by dynamic trimerization of aromatic nitriles, such as 1,4-dicyanobenzene (DCB), 1,3,5-tris(4-cyanophenyl)benzene (TCPB) and 2,6 -Dicyanopyridine (DCP) under ionic thermal conditions (ZnCl₂, 400 °C), where ZnCl₂ is used as a solvent and catalyst for the trimerization reaction.

Figure 1. Trimerization of dicyanobenzene in molten ZnCl₂ to trimers and oligomers and then to a covalent triazine-based framework. [1]

• Catalytic coupling reaction

CTF can also be prepared by Pd-catalyzed coupling reaction. For example, through the Suzuki coupling of 2,4,6-tris(4-bromophenyl)-1,3,5-triazine and aromatic monomers or trimerization of dicyanobenzene derivatives, the synthesis has a similar structure the two series of CTF.

Figure 2. Synthetic scheme based on covalent triazine-based framework (CTFs) by Suzuki-Miyaura type polycondensation. [2]

Applications

• CTFs have been used in a range of applications, such as CO₂ capture and storage, photocatalysis, and energy storage. In the field of photocatalysis, CTFs are mainly used in applications such as photoredox organic synthesis, water splitting, CO₂ photoreduction, and H₂O₂ generation.
• Water splitting photocatalyst

Modeling of optical and electronic structures has recently shown that some CTFs, namely CTF-0 and CTF-1, have frontier orbits that span the reduction and oxidation potentials of water, while having energy conversion narrow enough for visible light excitation. Combined with their porous morphology, their photoelectric properties make them promising photocatalysts for water splitting.

Figure 3. The structural motifs of the covalent triazine frameworks CTF-0, CTF-1 and CTF-2 (above) and their calculated electronic structures (below). [3]

References

1. Guigang Zhang. (2016). "Conjugated Polymers: Catalysts for Photocatalytic Hydrogen Evolution," Angewandte Chemie International Edition 55(51): 15712-15727.
2. Christian B.Meier. (2017). "Structure-property relationships for covalent triazine-based frameworks: The effect of spacer length on photocatalytic hydrogen evolution from water," Polymer 126: 283-290.
3. Vijay S. Vyas. (2016). "Soft Photocatalysis: Organic Polymers for Solar Fuel Production," Chemistry of Materials 28(15): 5191-5204.