Synthesis of a hydrophilic covalent-organic framework@silica composites via oxidation reaction for mixed-mode liquid chromatographic separation

Specifically, the oxidation of imine linked TAPT-TA-COF@SiO2 was prepared using 2,4,6-tris (4-aminophenyl-1,3,5-thiazine (TAPT) and 1,4-benzenedicarboxaldehyde (TA) as monomers through one pot cascade polymerization reaction on the surface of silica spheres, was carried out with high yield and specificity. Notably, its BET specific surface area and the pore size distribution of the spheres retained mesoporous similarly to the original porous silica microspheres obtained in this work. Chromatographic performance and multiple retention mechanisms were investigated, demonstrating efficient separation of neutral polar solutes and nonpolar compounds in reverse-phase chromatography mode than that achieved with the unmodified COF. Moreover, an improved separation method was established for representative saccharides and complex oligosaccharide samples confirmed that the post-modification amide TAPT-TA-COF@SiO2 based core-shell stationary phases were hydrophilic than imine-linked TAPT-TA-COF@SiO2 materials. These findings provide new opportunities for advancing the understanding of COF as HILIC stationary phases for separations, contributing to the application of COF in separation science.