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 [Cu2 (d-Cam)2 (4,4'-bpy)]n @SiO2 composite for high-performance liquid chromatography enantioseparation to overcome the above-mentioned problems. The [Cu2 (d-Cam)2 (4,4'-bpy)]n @SiO2 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 SiO2 microspheres and the chiral recognition ability of [Cu2 (d-Cam)2 (4,4'-bpy)]n 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 [Cu2 (d-Cam)2 (4,4'-bpy)]n @SiO2 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 [Cu2 (d-Cam)2 (4,4'-bpy)]n @SiO2 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.

Chiral core-shell microspheres ß-CD-COF@SiO2 used for HPLC enantioseparation.

Chiral covalent organic frameworks (CCOFs) have potential application in enantioseparation due to their advantages, such as large surface area, abundant chiral recognition sites and good chemical stability in organic solvents. However, the application of CCOFs in high performance liquid chromatography (HPLC) for enantioseparation has been rarely reported because of the shortcomings of CCOFs, such as light weight, irregular shape, and wide particle size distribution. In order to overcome the above shortcomings, a one-pot synthetic method was adopted to prepare a core-shell composite (ß-CD-COF@SiO2) via the growth of chiral ß-CD COF on the surface of amino-functionalized SiO2 microspheres. The as-prepared ß-CD-COF@SiO2 microspheres were used as a stationary phase for HPLC enantioseparation. The resolution ability of the ß-CD-COF@SiO2-packed column toward various chiral compounds was investigated using n-hexane/isopropanol as the mobile phase. The results show that the chiral ß-CD-COF@SiO2-packed column exhibited excellent chiral recognition ability for 24 pairs of chiral compounds with good reproducibility. These successful applications indicate that the preparation of the chiral COFs@SiO2 core-shell microspheres as a novel stationary phase for enantioseparation has good application prospects in HPLC.

A label-free and sensitive photoluminescence sensing platform based on long persistent luminescence nanoparticles for the determination of antibiotics and 2,4,6-trinitrophenol.

The rapid detection of pollutants with high sensitivity and selectivity is of considerable significance for security screening, environmental safety, and human health. In this study, we prepared persistent luminescence nanoparticles (PLNPs) and constructed a label-free sensor for sensitive and selective detection of pollutants in real samples and test papers. Following excitation, PLNPs could store absorbed light energy and release it in the form of luminescence. Compared with a fluorescence-based technique, a PLNPs-based measurement could effectively avoid background interference. Under optimal conditions, the limit of detection for TNP was found to be 10 nM, while for an antibiotic it was 5 nM. The nanoprobe was successfully applied for the detection of pollutants in real samples including milk and Dianchi Lake water samples. Due to the long-lasting afterglow nature of PLNPs, the signal-to-noise ratio could be greatly increased in complex real samples. By hand-writing with TNP solution as ink on filter paper, the photoluminescence (PL) of the part stained with TNP was immediately quenched. Moreover, after direct exposure under a UV lamp for 10 min and without further excitation, the luminescence of the test paper was investigated to avoid interferents. This PLNP material could be potentially employed as a multi-responsive luminescent sensor. In addition, these easy-to-use visual techniques could provide a powerful tool for a convenient POC assay of organic pollutants.