Enhancing the Separation Performance of COF@Silica Stationary Phase through Modification with Poly(Ionic Liquid) in Multi-Mode Liquid Chromatography

A stable and high-performance stationary phase is essential to achieve high-resolution separation of complex samples. Covalent organic framework (COF) has superior physicochemical properties and outstanding potential for application in chromatographic separation. However, hydrophilic selectivity and structural stability of COF pose concerns. Composites of COF with poly(ionic liquid) (PIL) are a promising solution to these problems. In this study, silica was first decorated with COF DVA-TAPB to obtain COF DVA-TAPB @SiO 2 microspheres (DVA and TAPB represent 2,5-diethenyl-1,4-benzenedicarboxaldehyde and 1,3,5-tris(4-aminophenyl)benzene, respectively). Subsequently, PIL-modified COF DVA-TAPB @SiO 2 (PIL/COF DVA-TAPB @SiO 2 ) microspheres were prepared by polymerization of 1-sulfopropyl-3-vinylimidazolium chloride ionic liquid onto COF DVA-TAPB @SiO 2 . The obtained PIL/COF DVA-TAPB @SiO 2 microspheres served as a multi-mode chromatographic stationary phase and efficiently separated various hydrophobic and hydrophilic analytes. Owing to the synergistic effects between COF DVA-TAPB and PIL, the separation performance of PIL/COF DVA-TAPB @SiO 2 column was significantly superior than COF DVA-TAPB @SiO 2 and PIL/SiO 2 columns. Additionally, the PIL/COF DVA-TAPB @SiO 2 column demonstrated good stability and reproducibility, with intra-day relative standard deviations for retention time <0.14% ( n  = 10) and peak area <1.64% ( n  = 10) following nearly 1000 continuous injections. This study not only endows functional COF with specific properties, but also paves a new path for the efficient separation and analyses of complex samples.