Programming Photocatalytic Reactivity in Quinoline-Based Covalent Triazine Frameworks

The rational development of metal-free photocatalytic nanomaterials with tunable electronic properties is key to advancing sustainable energy conversion and chemical synthesis. In this work, we report a family of quinoline-based covalent triazine frameworks , denoted as CTF-Quin, obtained through deliberate modification of substituents and backbone structure. By integrating electron-donating groups such as methoxy groups or electron-withdrawing groups such as trifluoromethyl units, in addition to the phenyl-to-pyridine substitutions, we achieve precise control over light absorption, band structure, and excited-state behavior.

Spectroscopic studies show that methoxy functionalization elevates the valence band, reduces the band gap, and facilitates charge separation, thereby enhancing electron-transfer-driven photocatalysis. In contrast, incorporation of pyridine units stabilizes the frontier molecular orbitals and improves structural planarity, favoring energy-transfer pathways. As a result, these materials display divergent photocatalytic functions: methoxy-substituted CTFs exhibit efficient hydrogen evolution, reaching rates up to 1,446 μmol h⁻¹ g⁻¹, whereas pyridine-containing frameworks enable selective oxidation of furfuryl alcohol to 5-hydroxy-2(5H)-furanone via singlet oxygen generation. Density functional theory calculations further corroborate the observed correlations between structure, properties, and catalytic performance.

Overall, this study highlights the potential of molecular-level design in covalent organic frameworks to direct photocatalytic selectivity toward targeted sustainable transformations.

References:

[1] Sánchez et la., ACS Applied Engineering Materials. Submitted