Syntheses,Structures And Properties Of Terbium-and D¹⁰Metal-Organic Frameworks Constructed By Tetrafluorobiphenyl Dicarboxylate Ligand

In the past decades,MOFs showcase the significant development in the gases separation.It has been reported that the gas separation can be realized by the molecular size effect via regulating the pore sizes of the MOF.In addition,by functionalization of the pore surfaces,the functional groups can be introduced into the MOF for sorption of a specific gas but with a low adsorption interaction with other gas.Thus the gas separation of mixtures is achieved.In this thesis,the fluorinated ligand of 3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylic acid（H₂TFBPDC）ligand was selected for building MOFs.The carboxylate oxygen atoms coordinate to the metal cneters to form the framewors of the MOFs.The F atoms act as the functional groups for the guest molecules.The introduction of the organic fuloro-ligand into the MOFs broadens the diversity of the fluorinated MOFs.Ten MOFs based on the 3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylate ligand with the terbium（III）,cadmium（II）,and zinc（II）as metal centers are provided in this thesis.Firstly,five MOFs constructed from terbium（III）and 3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylate ligand are presented.Compound Tb（1）contains one-dimensional（1D）right-handed Tb-carboxylate chains,which are further linked by the 3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylate ligand to form a three-dimensional（3D）framework.The 3D framework has 1D channels with the inner walls decorated with fluorine functional group,which provides an active site for the separation of gases.The adsorption selectivities both are 3.1 for 1/99 and 0.1/99.9 propyne/propylene mixtures at 298 K and 1 bar.The column-breakthrough experiments demonstrate that compound Tb（1）exhibits excellent propyne/propylene separation performance.The modeling studies using density functional theory show the preferential binding sites for propyne are the exposed fluorine atoms on the pore surface in 1D channels.Thus we demonstrate first example of MOF with organic fluoro ligand showing efficient separation toward propyne/propylene through functionalized MOF with organic fluorine.Compound Tb（2）is a 3D framework based on the linear Tb-carboxylate chains.The 3D structure of Tb（2）has 1D channels.Compound Tb（3）is a two-dimensional（2D）layer.The 2D layers are packed in an off-set fashion into a 3D nonporous structure.Each hexanuclear Tb₆（μ₃-OH）₈]units is linked by twelve 3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylate ligands to give a 3D framework featuring small tetrahedral cages and large octahedral cages for Tb（4）.The compound Tb（4）is a good material for storing propyne and separating propyne/propylene and propyne/propane.In compound Tb（5）,Each hexanuclear Tb₆（μ₃-OH）₈]units is connected by eight3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylate ligands to form a two-fold interpentrate3D framework.The presence of the two-fold interpentrate 3D netowrks in compound Tb（5）leads to almost nonporous structure.Secondly,The cadmium（II）and zinc（II）compounds with the 3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylate ligand.In compound Cd（6）has a dinuclear[Cd₂（ad）₂]unit,which is bridged by 3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylate ligands to form a 1D chain.Compound Cd（7）is a nonporous two-fold interpentrate 3D framework formed from the Cd-carboxylate chains linked by 3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylate ligands.Compound Cd（6）and Cd（7）display luminescent emissions.Compound Zn（8）is based on the dinuclear paddle-wheel[Zn₂（COO）₄]units,which are bridged by the 3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylate ligands and the triethylene diamine ligands to form a two-fold interpentrate 3D netowrks.In compound Zn（9）,the imidazole and the 3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylate ligands link the zinc（II）atoms to form a 3D structure with 1D channels.In compound Zn（10）,each octanuclear cluster unit is linked by eight 3,3’,5,5’-tetrafluorobiphenyl-4,4’-dicarboxylate ligands to form a two-fold interpentrate 3D structure with 1D channels.Attempts to access the open pores of compound Zn（8）,Zn（9）and Zn（10）are not successful,leading to a failure for accessing the gas adsorption and separation performance.