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

The unique features of uniform and adjustable cavities, abundant chiral active sites, and high enantioselectivity make chiral metal-organic frameworks popular as an emerging candidate for enantioselective separation. However, the wide particle size distribution and irregular shape of as-synthesized metal-organic frameworks result in low column efficiency, undesired chromatographic peak shape, and high column backpressure of such metal-organic frameworks packed columns. Herein, we report the fabrication of chiral core-shell microspheres [Cu (d-Cam) (4,4'-bpy)] @SiO composite for high-performance liquid chromatography enantioseparation to overcome the above-mentioned problems. The [Cu (d-Cam) (4,4'-bpy)] @SiO packed column gave high-resolution separation of racemates under low column backpressure (10-22 bar), indicating its synergistic effect of the good column packing property of the SiO microspheres and the chiral recognition ability of [Cu (d-Cam) (4,4'-bpy)] crystals. Thirteen kinds of chiral compounds including alcohols, amines, ketones, epoxides, and organic bases were well separated with good peak shapes and high column efficiency (18200 plates/m for 1-(9-anthryl)-2,2,2-trifluoroethanol) on the [Cu (d-Cam) (4,4'-bpy)] @SiO packed column. Among them, seven pairs of enantiomers achieved baseline separation and the resolution value for 1-(9-anthryl)-2,2,2-trifluoroethanol reached 11.22. Some effects such as column temperature, and analytes mass on the enantioseparations have been investigated. In addition, the [Cu (d-Cam) (4,4'-bpy)] @SiO packed column exhibited good stability and repeatability for the separation of chiral compounds. The relative standard deviations for five replicate separations of 1-phenylethanol were less than 1.0, 1.5, 3.0, and 2.0% for the retention time, peak area, number of theoretical plates, and resolution, respectively. The research results demonstrated the development of chiral metal-organic frameworks core-shell microspheres composite provide a promising platform for their practical application in chiral separation fields.