Synthesis And Properties Of Metal-organic Frameworks Materials Constructed By Amido-ligands

MOFs are a class of inorganic-organic hybrid crystalline materials constructed by coordination bonds between metal ions or clusters and organic ligands.They posses feature such as porosity,regular structure,high surface area,and tunable pore structure,exhibiting excellent properties in chemical catalysis,fluorescence sensing,adsorption and separation,biological imaging,and proton conduction.The choice of organic ligands has a significant impact on the structure and properties of the compound.Carboxylic acid ligands can not only coordinate well with metal ions but also act as bridging ligands when synthesizing MOFs with novel structures.With the increasing number of MOFs（metal-organic frameworks）and the growing demand for MOFs with specific properties,organic ligands with only carboxylic acid functional groups cannot meet experimental requirements.Therefore,on the one hand,the length of the ligands is extended to change the properties and increase the surface area of the pores.On the other hand,functional groups such as-OH,-NH₂,-CONH-,and-X（X=Cl,Br,I）are introduced to alter the interaction between the original ligands and guest molecules,thereby achieving property enhancement and modification.Among various functional groups,the-CONH-group can serve as both a hydrogen bond acceptor（carbonyl）and a hydrogen bond donor（amino）,significantly improving the properties of MOFs.Additionally,the-CONH-group can act as an excellent linking group by elongating the ligands.Moreover,the nitrogen atom in the pyridine group can easily form a coordination bond with transition metals.In this study,six different MOFs were synthesized by using a pyridine carboxylic acid ligand,5-（isophthalic acid）isonicotinamide,linked by an amide group,with transition metals and lanthanide metals as the metal centers.The structural differences of the synthesized compounds under different conditions were studied,followed by property investigations of two of the compounds.This paper is divided into four parts,and the specific content of each part is described below.Chapter 1 mainly introduces the research background of MOFs（including development history,synthesis methods,application fields）as well as the purpose and significance of topic.Chapter 2 In this chapter,we synthesized three different MOFs under solvothermal conditions using the transition metal Cu²⁺as the metal center and 5-（isophthalicamido）isophthalic acid as the ligand.The three MOFs,namely[Cu(C₁₄H₉N₂O₅)·0.5DMF·0.25C₂H₅OH]（1）,[Cu(C₁₄H₇N₂O₅)·5H₂O·DMF]（2）,and[Cu(C₁₄H₇N₂O₅)·3H₂O]（3）.All three compounds exhibited a three-dimensional network structure,with compound 2 demonstrating excellent CO₂/CH₄ gas separation performance.In Chapter 3,we synthesized three different MOFs materials under solvothermal conditions,using lanthanide metal ions Eu³⁺and Tb³⁺as the metal centers,and 5-（isophthalic acid amide）isophthalic acid as the ligand.The molecular formulas of these compounds are{[Tb₂(C₁₄H₉N₂O₅)₃·H₂O]·DMF}（4）,[Eu₂(C₁₄H₇N₂O₅)₃·2H₂O]（5）,and[Eu₂(C₁₄H₇N₂O₅)₂·3DMF·H₂O]（6）.We characterized their structures and basic properties and found that all three compounds exhibit fluorescence properties.Based on the more regular structure and excellent fluorescence performance and stability of compound 4,we studied its ability to detect metal cations.The experimental results showed that compound 4 has excellent detection ability for Fe³⁺.In Chapter 4,we summarized the conclusions of our experimental work in this thesis and provided an outlook for the future development of organic ligands containing amide groups in MOF material synthesis.