Chiral metal–organic framework [Zn2(D-Cam)2(4,4′-bpy)]n@SiO2 core–shell composite for HPLC separation

Chiral metal–organic frameworks, an emerging type of chiral porous materials, possess many outstanding characteristics such as high surface area, tunable pore sizes, and good chemical stability. Herein, we prepared a chiral [Zn 2 (D-Cam) 2 (4,4′-bpy)] n @SiO 2 core–shell composite on the SiO 2 -NH 2 microspheres by an in-situ growth method. The prepared [Zn 2 (D-Cam) 2 (4,4′-bpy)] n @SiO 2 -packed column exhibited high-resolution separation of racemic compounds and positional isomers at a low column backpressure (9–12 bar). Twelve pairs of enantiomers including alcohols, amines, epoxides, ketones, and esters were well resolved with sharp peak shapes on the [Zn 2 (D-Cam) 2 (4,4́-bpy)] n @SiO 2 chromatographic column. Compared the separation performance of [Zn 2 (D-Cam) 2 (4,4́-bpy)] n @SiO 2 -packed column and two chromatographic columns (commercial Chiralpak AD-H column and as-prepared SiO 2 -NH 2 column), the [Zn 2 (D-Cam) 2 (4,4′-bpy)] n -packed column and the commercial Chiralpak AD-H column have a good complementarity in chiral separation, and it also offered better separation performance compared to the SiO 2 -NH 2 column for separating positional isomers. The effects of column temperature and analyte mass on the HPLC separation were investigated. Additionally, the [Zn 2 (D-Cam) 2 (4,4́-bpy)] n @SiO 2 packed column has good repeatability and stability for HPLC separation of enantiomers and positional isomers. The relatvive standard deviations (RSDs) for repeated separations of 2,2,2-trifluoro-1-(9-anthryl)ethanol and o , m , p -bromoaniline were less than 0.8 % and 1.2 % for the retention time and peak area, respectively. After continuous use for one month, the RSDs for the retention time and peak area of them were in the range of 1.1–1.3 % and 1.5–1.8 % (inter-day and intra-day, n = 5), respectively. This work also indicates that the chiral MOFs@SiO 2 composites are promising for HPLC separation.