Effect of triazine-containing amine linker length on dye-selective photocatalysis in Tp-based COFs

A series of Tp-based covalent organic frameworks (COFs) with four amine linkers of different lengths were synthesized to investigate the structural factors governing photocatalytic dye decolorization. The linker length strongly affected the surface area and adsorption capacity of the COFs. COF with medium linker lengths exhibited higher activity toward methyl orange (MO), whereas the COF with the shortest linker showed the highest activity toward rhodamine B (RhB). This difference arises from the different dominant reactive species involved in the decolorization of each dye. For RhB, hole-driven oxidation was the dominant pathway, and COFs capable of generating holes with stronger oxidative power exhibited superior activity. In contrast, the COF lacking a triazine unit showed minimal activity toward either dye, likely due to inefficient interfacial electron transfer caused by electron delocalization and insufficient adsorption. These findings demonstrate that amine linker structure plays a crucial role in controlling dye selectivity and photocatalytic behavior in COFs.