C18 Chain Post-modified Covalent Organic Framework Functional Silica Reversed-Phase Chromatographic Stationary Phase for Pharmaceutical Analysis

Covalent organic frameworks (COFs) have numerous advantages, including high specific surface area, good stability, and ease of modification. These features have generated significant interest in utilizing COFs as chromatographic stationary phase materials. Herein, two monomers, 1,3,5-tris-(4-aminophenyl) triazine (TAPT) and 1,3,5-benzenetricarboxaldehyde, are selected to construct the COF material. A novel core–shell type composite material named SiO₂@COF was prepared with the covalent triazine framework layer grafted on the silica by in situ growth method, and then the C18 chain was post-modified on the SiO₂@COF material, named SiO₂@COF-C18. Multiple methods have been employed to illustrate the morphological and structural characteristics of the SiO₂@COF-C18 material. Then, several analytes, including anilines, polycyclic aromatic hydrocarbons (PAHs), alkylbenzenes, and positional isomers, were selected to study the separation mechanism of the SiO₂@COF-C18 column, which demonstrated that these analytes were separated on the SiO₂@COF-C18 column under chromatographic modes of hydrophobic interaction, π-π interaction, steric hindrance effect, etc. The prepared chromatographic column had excellent repeatability and high separation efficiency, and it was used to determine acetaminophen tablets under reversed-phase conditions. These results open a new avenue for the post-modification of hydrophobic groups on COF materials for pharmaceutical analysis.