2D metal-organic framework nanosheets-assembled core-shell composite material as stationary phase for hydrophilic interaction liquid chromatography.

The core-shell composites were first prepared by surface modification of silica spheres with two-dimensional MOF-FDM-23 nanosheets via a simple approach. The successful immobilization of 2D MOF-FDM-23 on the silica (2D MOF-FDM-23@silica) was confirmed by series of method including elemental analysis, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and the Brunauer-Emmett-Teller (BET). The obtained material showed excellent separation performance for multiple polar compounds such as sulfonamides, alkaloids, antibiotic and amino acid compounds etc. In addition, it was found to be superior to most reported MOF-based stationary phases in terms of separation performance, preparative reproducibility and chromatographic stability. The reproducibility of material preparation was demonstrated by the difference in retention time of the same mixture on three batches of the material at different times. The relative standard deviation (RSD) of the retention time for preparation repeatability was found to range from 0.5% to 1.4%. In short, the core-shell composite material prepared by this method broadened the application of MOF-based composites as chromatography stationary phase, and significantly developed the field of 2D MOF nanosheets in chromatography.