Striped covalent organic frameworks modified stationary phase for mixed mode chromatography

Covalent organic frameworks (COFs) have showed expected potential in chromatographic separation due to unique structure and excellent performance. Nowadays, COF materials applied as chromatographic stationary phases is still in its infancy. Here, we modified COF materials on silica using benzene-1,4,5-tetracarboxylic dianhydride (PMDA) and 1,3,5-tris-(4-aminophenyl)triazine (TAPT) monomers by one-pot synthetic method for performing mixed-mode function, named as SiO2@COF. Five characterization methods including thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), elemental analysis (EA) and powder X-ray diffraction (XRD) verified the morphology, structure characteristics and physicochemical properties of the materials. SiO2@COF for performing the separation of polar and nonpolar analytes on high performance liquid chromatography (HPLC) achieved the desired results. Retention mechanisms of the constructed SiO2@COF were researched via observing the effects of mobile phase with retention times. Results exhibited that the prepared stationary phase can provide various interaction modes, including hydrophobic, hydrophilic, hydrogen bonding and π-π interactions. In conclusion, the prepared SiO2@COF stationary phase can execute mixed-mode separation abilities and show potential for complex samples analysis.