Preparation of novel chiral stationary phases based on chiral metal-organic cages enable extensive HPLC enantioseparation

Background: The metal organic cages (MOCs) are an emerging type of porous material that has attracted considerable research interest due to their unique properties, including good stability and well-defined intrinsic cavities. The chiral MOCs with porous structures have broad application prospects in enantiomeric recognition and separation. However, there are almost no relevant reports on chiral MOCs as chiral stationary phases (CSPs) for enantioseparation by high-performance liquid chromatography (HPLC). Results: Here, we report for the first time, the chiral MOCs, MOC-PA was “wrapped” onto the silica gel to create a novel HPLC CSP of chiral MOC-PA@SiO₂ through wrapped in net method. There are 24 and 20 chiral compounds or chiral drugs, including alcohols, diols, esters, ketones, alkene, epoxides, ethers, organic acids, phenols and amines, were enantioseparated by vary degrees on MOC-PA@SiO₂ packed column under both normal phase (NP) and reversed phase (RP) modes, respectively. Furthermore, compared with commercial Chiralpak AD-H and Chiralcel OD-H columns, the MOC-PA@SiO₂ packed column exhibits well chiral separation complementarity to them. It can separate some racemates that unable to be or not to be well separated by the Chiralpak AD-H and Chiralcel OD-H columns. Besides, there are four positional isomers were also well separated by MOC-PA@SiO₂ packed column. Significance: The effects of temperature and injection volume on separation of MOC-PA@SiO₂ packed column were further investigated. This column also exhibited excellent repeatability, stability and column-to-column reproducibility on separation in HPLC. This work indicates that chiral MOCs are a promising class of chiral materials to prepare new CSPs for HPLC enantioseparation.