Fabrication of two-dimensional metal-organic framework nanosheets/PDA composites as mixed-mode stationary phase for chromatographic separation.

The synthesis of two-dimensional metal-organic frameworks (2D MOFs)/polymer core-shell composites is reported which were composed of polydopamine modified 2D Zr-1,3,5-(4-carboxylphenyl)-benzene (2D Zr-BTB) nanosheets and silica microspheres via a double-solvent approach. In this way, the composites were obtained under the condition of two solvents with different polarities to avoid agglomeration and uneven modification of most MOFs particles on the surface of the silica, existing inevitably in the one-pot method. Compared with the reported MOFs@silica composites adopting one-pot solvent method, the prepared composites exhibited significantly enhanced separation performance for sulfonamides, antibiotics, nucleosides, and polycyclic aromatic hydrocarbons compounds. Furthermore, the retention mechanisms were demonstrated by studying the relationships of chromatographic retention factors of tested analytes versus a variety of parameters under RPLC and HILIC modes, respectively. The superior chromatographic repeatability and stability were validated through the relative standard deviations of the retention time and/or column efficiency, which were found to be less than 0.8% and 0.9%, respectively. The material showed efficient separation ability for several types of compounds and provided another selectivity for preparing composites based on 2D MOFs nanosheets and other functional molecules.