Structural Transformation,radical Generation And Chiral Resolution Of Cd-MOF Under External Electric And Magnetic Fields

Metal organic frameworks(MOFs)are structures formed by self-assembly of metal centers and organic ligands.This feature enables them to have almost unlimited adjustability in terms of component diversity and structural hierarchy,and can be widely used in gas adsorption and separation,drug delivery,and catalysis.In stereochemistry,structural transformation often produces different chemical and physical properties.Therefore,controlling the synthesis of MOF with different forms plays a very important role in regulating the properties of MOF.Currently,the mostly methods for changing the structure of MOF are through chemical means,such as controlling the structure of metal ions and organic ligands,controlling the reaction temperature and time,controlling the molar ratio between reactants,and selecting the reaction solvent.However,the application of physical fields to the structural modification of MOF has not been seen.Therefore,based on the study of MOF structures,this thesis reports a series of results on the transformation of Cd-MOF structures induced by external electric and magnetic fields.In addition,,the corresponding structures were characterized by ~1H NMR,FT-IR,X-ray single crystal diffraction,PXRD powder diffraction,TAG thermogravimetric analysis,solid-state fluorescence spectroscopy,electron paramagnetic resonance,circular dichroism spectrum,and the adsorption properties were studied by surface area test in this thesis.ⅠBy introducing an applied weak electric field,the structure of Cd-MOF based on4-amino-3,5-bis(4-pyridyl-3-phenyl)-1,2,4-triazole ligand was composed for the first time.The reasons for the structural transition from three-dimensional to two-dimensional and the property effects of the structural transition were studied.ⅡBased on a porous three-dimensional Cd-MOF-1 structure,stable single electron radicals were generated through excitation induced by a superimposed electric field.The source of single electron free radicals was verified through the adsorption of oxidation-reduction inert benzene and toluene gases,as well as the study of electron paramagnetic resonance and solid-state fluorescence emission spectroscopy.ⅢIn according to the research of chiral MOF,a strategy for controlling the self-assembly of Cd-MOF based on the interaction of electric and magnetic fields(Lorentz forces)was designed,and achieved controllable self-assembly from an chiral ligand to a single chiral MOF.On this basis,CD signal induction of chiral CD-MOF by non-chiral guest aniline was completed.ⅣCombining the coordination ability of pyridine and carboxylic acid,three ligands with pyridine and carboxylic acid as the multiple coordination terminal group were designed and synthesized.And several examples of pyridine carboxylic acid MOF crystals with extremely high thermal stability were synthesized.In summary,we have studied the effects of external electric and magnetic fields on the stability of three-dimensional Cd-MOF-1 structures,as well as the effects of chelating coordination methods on the stability of MOF.Finally,we have completed the characterization of their structures through X-ray single crystal diffraction and other auxiliary tools.