Xu Ruiping, Hu Jian, Liu Yanjuan, Zhang Yuefei, Chen Wei, Tang Sheng
School of Chemistry and Environmental Engineering, Wuhan Institute of Technology, Wuhan 430205, China.
College of Medicine, Linyi University, Linyi 276000, China.
J Chromatogr A. 2025 Sep 13;1758:466185. doi: 10.1016/j.chroma.2025.466185. Epub 2025 Jul 1.
Covalent organic frameworks (COFs), featuring high surface reactivity and robust stability, are promising candidates for chromatographic stationary phases. However, the abundant aromatic groups in COF may lead to overly strong interactions with hydrophobic analytes, causing chromatographic peak tailing and low column efficiency. Moreover, the limited hydrophilicity of the conventional COF material results in insufficient separation ability of COF@SiO composites for polar substances, thereby restricting their wide applicability. With the aim of improving the flexibility, selectivity and separation efficiency of COF@SiO, a hydrophilic nanohydrogel (NHG) was modified on the surface of COF. Firstly, COF@SiO was synthesized via a mild one-pot approach using the eco-friendly deep eutectic solvent as the reaction medium. Subsequently, NHG-COF@SiO composite material was fabricated through the surface modification of COF@SiO with poly(N-isopropylacrylamide)-based NHG. Hydrophilic/hydrophobic compounds (nucleoside bases, sulfonamides, B vitamins, polycyclic aromatic hydrocarbons, alkylbenzenes and phenyl ketones), aromatic positional isomers, and ionizable benzoic acids were successfully separated by the NHG-COF@SiO in different chromatographic modes. The NHG functionalization significantly enhances chromatographic performance of COF@SiO by increasing the flexibility of COF material, while COF reciprocally modulates the strong hydrophilicity of NHG to improve separation selectivity. Leveraging its multifunctional interaction sites, the NHG-COF composite demonstrates high-resolution separation performance. The synergistic integration of NHG and COF has achieved a triple enhancement in hydrophilicity, selectivity and separation efficiency for the NHG-COF@SiO. This achievement facilitates the realization of multi-mode separation in a single-column system, serving as a valuable reference for the ongoing research on COF-based silica columns.
共价有机框架材料（COFs）具有高表面反应活性和强大的稳定性，是色谱固定相的理想候选材料。然而，COF中丰富的芳香基团可能导致与疏水性分析物的相互作用过强，从而引起色谱峰拖尾和柱效低下。此外，传统COF材料的亲水性有限，导致COF@SiO复合材料对极性物质的分离能力不足，从而限制了它们的广泛应用。为了提高COF@SiO的柔韧性、选择性和分离效率，在COF表面修饰了亲水性纳米水凝胶（NHG）。首先，以环保型低共熔溶剂为反应介质，通过温和的一锅法合成了COF@SiO。随后，通过用基于聚（N-异丙基丙烯酰胺）的NHG对COF@SiO进行表面修饰，制备了NHG-COF@SiO复合材料。亲水性/疏水性化合物（核苷碱基、磺胺类药物、B族维生素、多环芳烃、烷基苯和苯酮）、芳香位置异构体和可电离的苯甲酸在不同的色谱模式下被NHG-COF@SiO成功分离。NHG功能化通过增加COF材料的柔韧性显著提高了COF@SiO的色谱性能，而COF则反过来调节NHG的强亲水性以提高分离选择性。利用其多功能相互作用位点，NHG-COF复合材料展现出高分辨率分离性能。NHG和COF的协同整合实现了NHG-COF@SiO在亲水性、选择性和分离效率方面的三重提升。这一成果有助于在单柱系统中实现多模式分离，为正在进行的基于COF的硅胶柱研究提供了有价值的参考。
