Capsule-Type Single-Crystal Covalent Organic Frameworks as an Advanced Chromatographic Stationary Phase for Efficient Separation of Isomers

Single-crystal covalent organic frameworks (SCOFs) with long-range ordered crystal structures have emerged as potential separation media for high-performance liquid chromatography (HPLC). Herein, capsule-type SCOFs (C-SCOFs) were synthesized at room temperature and directly utilized as a stationary phase for HPLC. Owing to its regular morphology, excellent monodispersity, outstanding chemical stability, organized pore structure, and pronounced hydrophobicity, C-SCOFs packed column could not only efficiently separate hydrophobic molecules with outstanding column efficiency but also achieved baseline separation of 15 isomers with similar physicochemical properties, including iodoanisole isomers, iodotoluene isomers, and iodobenzotrifluoride isomers. Especially, the column efficiencies of 50700-60600 plates/m were achieved for xylene isomers and the resolution values for <i>o</i>-/<i>m</i>-xylene and <i>m</i>-/<i>p</i>-xylene were 1.85 and 3.08, respectively. In comparison with the commercial C18 column and the polycrystalline COF packed column, the separation performance of the C-SCOFs packed column showed better advantages in isomer separation. Furthermore, the C-SCOFs packed column was applied to separate psoralen and isopsoralen from <i>psoralea corylifolia</i> and the phthalate esters (PAEs) in the river water sample, demonstrating the potential of C-SCOFs packed column for practical applications. This study not only promoted the development of SCOFs with unique structures as potential stationary phases for chromatographic analysis but also broadened the application of SCOFs.