A tale of two syntheses: a comparative study of the physical and photocatalytic properties of covalent triazine frameworks (CTFs)

TY - JOUR

T1 - A tale of two syntheses

T2 - a comparative study of the physical and photocatalytic properties of covalent triazine frameworks (CTFs)

AU - Nielsen, Mads Lund Nygaard

AU - Sharma, Ruchi

AU - Ceccato, Marcel

AU - Marks, Melissa Jane

AU - Frank, Sara

AU - Skibsted, Jørgen

AU - Catalano, Jacopo

AU - Lock, Nina

PY - 2025/10/30

Y1 - 2025/10/30

N2 - Covalent triazine frameworks (CTFs) have exhibited promising photocatalytic capabilities for organic transformations, CO2 reduction and water treatment, yet the links between synthesis procedure and structural- and catalytic properties are essentially unexplored. This study investigates CTF-1 type materials prepared by two distinct synthesis procedures: One variant of CTF-1 was synthesised via a solvent-assisted route over three days at 30 °C (CTF-1(SS)), while the other form was synthesised at 250 °C over 12 hours (CTF-1(DS)) followed by post-synthetic modification through either heat- or mechanical treatment for removal of excess triflic acid catalyst. All synthesised materials could be identified as different CTF-1 variants; however, the synthesis choice profoundly impacts the material properties. Pristine CTF-1(DS) is semicrystalline with good visible light absorption and high thermal stability. In contrast, CTF-1(SS) is amorphous with embedded amide functionalities and limited visible light absorption and thermal stability, which is attributed to a lower degree of polymerization/conjugation. Surprisingly, due to the embedded amide sites, the amorphous CTF-1(SS) exhibits higher photocatalytic activity than pristine CTF-1(DS) under UV light. However, CTF-1(DS) shows the best photocatalytic properties after post-synthetic removal of residual triflic acid. Heat treatment allows complete removal of residual acid, and ball-milling only achieves partial acid removal. This study, therefore, demonstrates that choosing appropriate methods for synthesis facilitates the enhancement of desired physical- and light absorption properties in CTF-1-based photocatalysts and that nuanced characterisation techniques are required to fully understand the photocatalytic behaviour of different CTF-1 variants.

AB - Covalent triazine frameworks (CTFs) have exhibited promising photocatalytic capabilities for organic transformations, CO2 reduction and water treatment, yet the links between synthesis procedure and structural- and catalytic properties are essentially unexplored. This study investigates CTF-1 type materials prepared by two distinct synthesis procedures: One variant of CTF-1 was synthesised via a solvent-assisted route over three days at 30 °C (CTF-1(SS)), while the other form was synthesised at 250 °C over 12 hours (CTF-1(DS)) followed by post-synthetic modification through either heat- or mechanical treatment for removal of excess triflic acid catalyst. All synthesised materials could be identified as different CTF-1 variants; however, the synthesis choice profoundly impacts the material properties. Pristine CTF-1(DS) is semicrystalline with good visible light absorption and high thermal stability. In contrast, CTF-1(SS) is amorphous with embedded amide functionalities and limited visible light absorption and thermal stability, which is attributed to a lower degree of polymerization/conjugation. Surprisingly, due to the embedded amide sites, the amorphous CTF-1(SS) exhibits higher photocatalytic activity than pristine CTF-1(DS) under UV light. However, CTF-1(DS) shows the best photocatalytic properties after post-synthetic removal of residual triflic acid. Heat treatment allows complete removal of residual acid, and ball-milling only achieves partial acid removal. This study, therefore, demonstrates that choosing appropriate methods for synthesis facilitates the enhancement of desired physical- and light absorption properties in CTF-1-based photocatalysts and that nuanced characterisation techniques are required to fully understand the photocatalytic behaviour of different CTF-1 variants.

UR - https://www.scopus.com/pages/publications/105020606655

U2 - 10.1039/d5nr02635k

DO - 10.1039/d5nr02635k

M3 - Journal article

C2 - 41090963

AN - SCOPUS:105020606655

SN - 2040-3364

VL - 17

SP - 24669

EP - 24681

JO - Nanoscale

JF - Nanoscale

IS - 42

ER -