Studies On Syntheses,Structures,and Properties Of Ln-MOFs Constructed By H₃NTB Ligand

Lanthanide-based metal-organic frameworks(Ln-MOFs),as a branch of MOF field,are hybrid porous materials composed of lanthanide ions or clusters connected to organic ligands through metal coordination bonds.Featuring adjustable structures and various properties,Ln-MOFs show excellent performance in gas storage and separation,luminescence,heterogeneous catalysis and so on.In this thesis,20 Ln-MOFs classified into six new struture types were obtained by the reaction of H3NTB ligands with lanthanide metal salts in different solvent systems,and their properties of gas adsorption,fluorescence,and organic catalysis were studied.The main work of this thesis is as follows:A series of 1-Ln have been synthesized by the reaction of H3NTB with lanthanide metal salts in DMA/H2O/HCl mixed solvents:{[La(NTB)(DMA)(H2O)]·(DMA)}n(1-La)and {[Ln(NTB)(DMA)]·(DMA)}n(1-Ln,Ln=Pr,Eu,Tb,Dy).The five compounds have massive crystal morphology,and structural analysis shows that they have the same threedimensional porous framework,and the micropore porosity is more than 40%.Ar and CO2 gas adsorption studies show that the BET specific surface areas of the five compounds are 136.1(1-La),120.5(1-Pr),262.6(1-Eu),273.0(1-Tb)and 224.9(1-Dy)m2·g-1,respectively,indicating that these compounds have significant stability and permanent porosity.More importantly,under solvent-free conditions,the catalytic activity of 1-Ln in the Knoevenagel reaction of benzaldehyde derivatives with malononitrile was further studied.It was found that 1-Tb had the highest catalytic activity(the yield was up to 99%).The Lewis acid site of Tb in the skeleton played a leading role in the Knoevenagel condensation reactions,providing a unique example for distinguishing the role of framework Ln ions in catalyzing Knoevenagel reactions.Interestingly,in some reactors,a needle-like compound 1-La-needle({[La(NTB)3(DMA)3]}n)can be obtained separately from H3NTB ligand and LaCl3·7H2O under the same reaction conditions.Structure analysis shows that 1-La-needle has a graphene-like two-dimensional layered structure,which is completely different from the three-dimensional frame structure of block 1-La,which reflects the flexible coordination mode of rare earth ions.A series of 2-Ln have been synthesized by the reaction of H3NTB with lanthanide metal salts in MMP/H2O/HCl mixed solvents:{[La3(NTB)3(NMP)(H2O)2]·(NMP)3}n(2La)、{[Pr(NTB)(H2O)2]}n(2-Pr)、{[Ce(NTB)(NMP)(H2O)]·(NMP)}n(2-Ce)and{[Ln(NTB)(NMP)]·(NMP)}n(2-Ln,Ln=Sm,Eu,Gd,Tb,Dy,Ho,Er,Yb,Lu).The 2-La complex belongs to monoclinic system,and the space group is P21/c.There are three different coordination environments for La3+.Three NTB3-ligands in the molecular unit also show three different types of coordination modes.La3+ions are linked by NTB3ligands to form a three-dimensional porous framework featuring interconnected porous cages.2-Pr complex belongs to monoclinic space group P2/n.Pr3+is eight-coordinated by two water molecules and five NTB3-ligands.Each NTB3-ligand coordinate with five neighboring Pr3+ions to form a three-dimensional porous framework.Interestingly,the porous framework 2-Pr is different from that of 2-La.The other 10 complexes are intrinsically isostructural with 1-Ln.The 12 complexes have remarkable stability and permanent porosity as shown by the adsorption of Ar and CO2.Their fluorescence properties are strongly dependent on the nature of ligand and lanthanide ions.The catalytic properties of 2-Ln are investigated in detail.the catalytic activity of 2-Ln towards catalyzing Deacetalization-Knoevenagel cascade reactions has been investigated.It is found that 2-Tb has the highest catalytic activity(the yield was 98%).The catalytic experiment of carbon dioxide cycloaddition by 2-Ln was further studied.It is found that the catalytic yield of epichlorohydrin and Prpylene Oxide by 2-Tb can be up to 97%and 96%,suggesting that 2-Tb is an effective and multifunctional heterogeneous catalyst which can catalyze a variety of organic reactions.A series of 3-Ln have been obtained by the reaction of H3NTB with lanthanide metal salts in NMF/H2O/HCl mixed solvents:{[Ln(NTB)3(H2O)2]·(NMF)3}n(3-Ln,Ln=Eu,Tb).3-Ln are isostructures structures belonging to the monoclinic space group P21/c.In 3Tb,each Tb3+is nine-coordination by two water molecules,while NMF molecule did not participate in the coordination but only acted as the guest molecule.Every two Tb3+is bridged by a μ2-η2:η1 carboxylate of the NTB3-ligand to form a dinuclear cluster unit Tb2(COO)4.The dinuclear clusters are linked by the ligand to form a double-layered structure.The adjacent layers are stabilized by the weak intermolecular force and the hydrogen bonds between the coordination water molecules and NMF molecules.