MOFs Mixed-mode Stationary Phases:Preparation And Its Chromatographic Separation Performances

Metal-organic frameworks?MOFs?are a new type of organic-inorganic hybrid porous crystalline materials.Due to their unique adjustable porous structure,high specific surface area,good chemical and thermal stability,MOFs materials exhibit great potential as the high performance liquid chromatography?HPLC?stationary phases.Herein,MOF-74@SiO₂ and ZIF-67@SiO₂ core-shell stationary phase materials were fabricated and further exploited for mixed-mode chromatographic separation and analysis.The full text is divided into four chapters.The first chapter includes four parts.The first part briefly describes the classifications of MOFs materials as well as their composites.The second part briefly describes the applications of MOFs materials as well as their composites.The third part briefly describes the applications of MOFs materials in the field of HPLC separation.The fourth part briefly describes the starting points and innovations of this work.In the second chapter,MOF-74@SiO₂ and ZIF-67@SiO₂ core-shell chromatographic stationary phase materials were fabricated via solvothermal method.Firstly,with2,5-dihydroxyterephthalic acid as the organic ligand and metal nickel as the metal center,MOF-74 material was in-situ coated on the surface of carboxyl-silica microspheres.Thus,MOF-74@SiO₂ core-shell chromatographic stationary phase material was prepared.Secondly,with 2-methylimidazole as the organic ligand and metal cobalt as the metal center,ZIF-67material was further coated on the surface of carboxyl-silica microspheres.Thus,ZIF-67@SiO₂ core-shell chromatographic stationary phase material was also prepared.The new materials were characterized by fourier transform infrared spectroscopy,X-ray diffraction,scanning electron microscopy,thermogravimetric analysis,elemental analysis,and Brunauer-Emmett-Teller?BET?specific surface areas and pore size analyzer,respectively.The results prove that the MOF-74@SiO₂ and ZIF-67@SiO₂ materials have been successfully prepared.In the third chapter,the MOF-74@SiO₂ material was further used for HPLC separation.Firstly,the retention mechanisms of the packed MOF-74@SiO₂ column were evaluated by hydrophilic thiourea compounds and nucleic acid base compounds,hydrophobic alkylbenzenes and polycyclic aromatic hydrocarbon compounds.The column exhibits reverse phase liquid chromatography and hydrophilic interaction liquid chromatography retention mechanisms.Thus,it can be used for mixed-mode chromatographic separation.The separation performances of the column was firstly investigated by hydrophobic alkylbenzene compounds,polycyclic aromatic hydrocarbon compounds,phenolic compounds and further compared with C₈ column.Moreover,the separation performances of the column were further investigated with polar sulfonamide compounds,veterinary drugs and further compared with silica-based column.The MOF-74@SiO₂ column can achieve rapid separation with good separation selectivity.The MOF-74@SiO₂ column was further used for the detection of illegally added hydrocortisone and prednisone in children's face cream as well as the veterinary drugs residues of sulfamethazine and sulfathiazole in the milk.In the future research,the chromatographic separation potential and application prospect of ZIF-67@SiO₂material will be explored.The fourth chapter summarizes the research contents of the full work.