Core-Shell Metal-Organic Frameworks as the Stationary Phase for Hydrophilic Interaction Liquid Chromatography

A strategy based on in situ growth of a metal-organic framework composite material was proposed by introducing a sodium dodecyl benzenesulfonate (SDBS) group to increase the electrostatic interaction between the MOF ligand and silica. In this work, mesoporous silica spheres were first functionalized with a zirconium(IV)-based metal-organic framework material (MOF-808), which produced a core-shell particle (MOF-808@silica) as a hydrophilic interaction liquid chromatography (HILIC) stationary phase. The obtained material improves and enhances the selectivity and stability of the stationary phase in traditional MOF-based HILIC. A series of methods such as elemental analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, and Brunauer-Emmett-Teller were used to confirm that MOF-808 was successfully modified onto silica. The relative standard deviation (RSD) of the retention time for stability with 120 h of continuous elution was found to range from 0.2% to 0.6%, and the RSD of the repeatability for 10 replicates of continuous elution was found to range from 0.1% to 0.3%. Furthermore, the column batch-to-batch reproducibility of the retention time was reproducible with an RSD of less than 2.2% depending on the analyte. The composite materials were found to be superior to most reported MOF-based stationary phases in terms of separation performance for various polar compounds, preparative reproducibility, and chromatographic stability. In short, MOF-808@silica composite material expands and improves the use of MOF materials as stationary phases in hydrophilic chromatography, revealing a method to prepare a MOF@silica composite that shows good performance when used for chromatographic analysis.