Chiral Metal–Organic Framework d-His-ZIF-8@SiO₂ Core–Shell Microspheres Used for HPLC Enantioseparations

Abstract

Chiral metal–organic frameworks (MOFs) have aroused great attention in the chiral separation field based on their excellent characteristics, including abundant topological structures, large surface area, adjustable pore/channel sizes, multiple active sites, and good chemical stability. However, the irregular morphology and nonuniformity of the synthesized MOF particles cause low column efficiency and high column backpressure for MOF-packed columns, which significantly affects their separation performance. Herein, we prepared a homochiral d-his-ZIF-8@SiO2 composite by growing of d-his-ZIF-8 on the carboxylic-functionalized SiO2 microspheres via a simple one-pot synthesis approach. The d-his-ZIF-8@SiO2 core–shell microspheres with uniform particles and narrow size distribution were applied as the chiral stationary phase (CSP) for enantioseparations in HPLC. Various racemates were separated on the d-his-ZIF-8@SiO2-packed columns with n-hexane/isopropanol as the mobile phase. Eighteen racemates including alcohol, phenol, amine, ketone, and organic acid were well resolved on the homochiral d-his-ZIF-8@SiO2 CSP. The d-his-ZIF-8@SiO2 core–shell microspheres’ CSP possesses an excellent chiral resolution ability toward various racemic compounds with good reproducibility and stability. Hence, the fabrication of chiral MOF@SiO2 core–shell microspheres is an effective strategy to improve the application of homochiral MOFs as CSPs in the field of chromatography.

Emerging Homochiral Porous Materials for Enantiomer Separation

“…[21] Furthermore, when TAMOF-1 crystals served as the CSP, they proved to have excellent chiral discrimination toward racemic trans-2,3-diphenyloxirane and the ability to separate racemates of other chiral compounds including 1-phenylethanol, benzoin, and flavanone, which outperformed several commercial chiral HPLC columns. Homochiral D-His-ZIF-8@SiO 2 microspheres were utilized as CSP by Yu et al [91] Homochiral D-His-ZIF-8 was in situ grown on Zn-BLD Methyl phenyl sulfoxide Baseline separation [86] [ZnLBr]•H 2 O Ibuprofen, 1-phenyl-1-propanol, 1-phenylethylamine and benzoin…”

“…Highest α ranging from 11.6 to 13.2 for chiral sulfoxides [90] D-his-ZIF-8@SiO 2 1-(1-Naphthyl)ethanol, benzoin, praziquantel, 1,1´-bi-(2-naphthol), trans-stilbene oxide, naproxen, 1-(9-anthryl)-2,2,2-trifluoroethanol and zopicloneBaseline separation for most analytes. Highest α of 7.13 for 1-(1-naphthyl)ethanol[91]…”

Chiral Detection with Coordination Polymers

“…Core-shell microspheres have also been developed for use as CSPs in HPLC enantioseparations, which build upon the previous ideas of MOF-silica composites. [22] These particles, synthesised by incorporating silica microspheres into the reaction mixture of histidine-modified ZIF-8, exhibited a uniform diameter of 5.5 μm, perfect for utilization as CSPs without any manual grinding. The resulting HPLC columns separated a total of eighteen racemates with separation factors up to 7.55, the highest yet documented.…”

A chiral metal‐organic framework core‐shell microspheres composite for high‐performance liquid chromatography enantioseparation

“…So far, a few examples of chiral MOF@SiO 2 core-shell composites as CSPs for HPLC enantioseparation. Recently, our group reported that two kinds of chiral MOF@SiO 2 core-shell composites including d-his-ZIF-8@SiO 2 [34] and [Co 2 (d-cam) 2 (TMDPy)]@SiO 2 [20] via an in-situ growth method used as CSPs for HPLC separation of racemates. These chiral MOF@SiO 2 core-shell composites packed columns exhibited high enantioselectivity and excellent chiral resolution ability toward many different kinds of enantiomers such as alcohols, amines, phenols, ketones, organic acids, organic bases, and so on.…”