Fabrication of ZIF-8@SiO2 Core–Shell Microspheres as the Stationary Phase for High-Performance Liquid Chromatography

The unique features of high porosity, shape selectivity, and multiple active sites make metal–organic frameworks (MOFs) promising as novel stationary phases for high-performance liquid chromatography (HPLC). However, the wide particle size distribution and irregular shape of conventional MOFs lead to lower column efficiency of such MOF-packed columns. Herein, the fabrication of monodisperse MOF@SiO 2 core–shell microspheres as the stationary phase for HPLC to overcome the above-mentioned problems is reported. Zeolitic imidazolate framework 8 (ZIF-8) was used as an example of MOFs due to its permanent porosity, uniform pore size, and exceptional chemical stability. Unique carboxyl-modified silica spheres were used as the support to grow the ZIF-8 shell. The fabricated monodisperse ZIF-8@SiO 2 packed columns (5 cm long × 4.6 mm i.d.) show high column efficiency (23 000 plates m −1 for bisphenol A) for the HPLC separation of endocrine-disrupting chemicals (bisphenol A, β-estradiol, and p -( tert -octyl)phenol) and pesticides (thiamethoxam, hexaflumuron, chlorantraniliprole, and pymetrozine) within 7 min with good relative standard deviations for 11 replicate separations of the analytes (0.01–0.39, 0.65–1.7, 0.70–1.3, and 0.17–0.91 % for retention time, peak area, peak height, and half peak width, respectively). The ZIF-8@SiO 2 microspheres combine the advantages of the good column packing properties of the uniform monodisperse silica microspheres and the separation ability of the ZIF-8 crystals. Graphical Core strength : Monodisperse ZIF-8@SiO 2 (ZIF-8=zeolitic imidazolate framework 8) core–shell microspheres have been fabricated through controllable growth of a ZIF-8 shell on spherical carboxylate-terminated SiO 2 cores (see figure). The metal–organic framework material is suitable as a stationary phase for fast and highly efficient HPLC separation.