Fabrication of Hierarchical Chiral Coordination Polymer-Based Stationary Phases for Enhanced HPLC Enantioseparation

The investigation of helical coordination polymers (CPs) with integrated molecular and mesoscale chirality as high-performance liquid chromatography (HPLC) chiral selectors is a crucial endeavor. Nevertheless, the related study has not been reported. Herein, we prepared a set of CPs that exhibited distinct morphologies, including nanofiber, twist ribbon, and superhelix with varying helical pitches. Subsequently, a series of new chiral stationary phases (CSPs) based on these chiral CPs were successfully fabricated by coating them onto the spherical aminated silica gel matrix. A systematic investigation into the separation performances of these CSPs was conducted via HPLC. By comparing the relationship between chiral CPs with different morphologies and their chromatographic separation abilities, we found that the superhelix possessing both molecular and mesoscale chirality exhibited the most superior chiral separation performance, capable of efficiently resolving nine racemic compounds with a maximum resolution of 3.62. However, the CSPs prepared from chiral CPs with nanofiber or twist ribbon morphologies displayed comparatively poor chromatographic separation abilities. Meanwhile, the chiral separation performance was markedly diminished for the dehelical polymer obtained through the thermal treatment of the superhelix, underscoring that mesoscale superhelical chirality is crucial for chiral recognition and separation. Additionally, we also found that the pitch sizes of the mesoscale superhelices have a significant internal connection with their chiral separation performances. This work not only identifies hierarchical chiral CPs with dual molecular and mesoscale helical chirality as promising chiral materials for chromatographic enantioseparation but also establishes that the introducing mesoscale superhelices and controlling their pitches precisely are key to boosting chiral separation efficiency.