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 COFDVA-TAPB to obtain COFDVA-TAPB@SiO2 microspheres (DVA and TAPB represent 2,5-diethenyl-1,4-benzenedicarboxaldehyde and 1,3,5-tris(4-aminophenyl)benzene, respectively). Subsequently, PIL-modified COFDVA-TAPB@SiO2 (PIL/COFDVA-TAPB@SiO2) microspheres were prepared by polymerization of 1-sulfopropyl-3-vinylimidazolium chloride ionic liquid onto COFDVA-TAPB@SiO2. The obtained PIL/COFDVA-TAPB@SiO2 microspheres served as a multi-mode chromatographic stationary phase and efficiently separated various hydrophobic and hydrophilic analytes. Owing to the synergistic effects between COFDVA-TAPB and PIL, the separation performance of PIL/COFDVA-TAPB@SiO2 column was significantly superior than COFDVA-TAPB@SiO2 and PIL/SiO2 columns. Additionally, the PIL/COFDVA-TAPB@SiO2 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.