Construction And Properties Of Metal-Organic Coordination Polymers Containing Nitrogen Heterocycles And Carboxyl Ligands

Coordination polymer（CP）is a class of hybrid functional material.In recent years,with the extensive exploration and in-depth research,CP has shown great advantages and good application potential in vairous fields,such as heterogeneous catalysis,adsorption,separation,luminescence and medicine.As is well known,the structure of the material plays a key role in its properties.For a long time,the structural design of complexes has attracted much attention and achieved some research results,but the introduction of functional clusters and the design and selection of functional ligands,as well as their effects on the properties of complexes still need to be further explored.Therefore,it is of great significance to realize the functionalization of complexes by introducing functional clusters and selecting target ligands.Based on this,nine metal-organic coordination polymers with novel structures were prepared by solvothermal method.The structures and properties of nine complexes were characterized and tested by a series of methods.The main results are as follows:（1）Under the guidance of reticular chemistry,the functional[Co₆（μ₃-OH）₆]cluster was immobilized into MOFs through the mixed ligand construction strategy and the fine regulation of reaction microenvironment,giving three pillar-layered[Co₆（μ₃-OH）₆]-based MOFs（Co₆-MOF-1～3）with regulable frameworks.These MOFs were characterized by X-ray single crystal diffraction and powder diffraction.In these Co₆-MOFs,the pore properties can be controlled due to the existence of the second ligand.The pore size is expanded from 8.8（?）to 13.4（?）,and the specific surface area is in the range of 1896 to 2401 m² g^-1.Due to the variable valence properties of[Co₆（μ₃-OH）₆]clusters,these MOFs can selectively catalyze the oxidation of styrene and benzyl alcohol with O₂ as oxidant,and show high conversion efficiency（>90%）and product selectivity（>80%）.（2）Using pyrazine and 2-aminopyrazine as pillar ligands,two isostructural pillar-layered MOF（Co₆-MOF-4 and Co₆-MOF-4-NH₂）were obtained by fine adjusting the reaction conditions.The Co₆-MOF-4-NH₂ was determined by single crystal diffraction.The effect of amino group on the performance of MOFs was investigated by CO₂ adsorption test and epoxide carbon dioxide cycloaddition experiment at different temperatures（273 K and 298 K）.The results show that the existence of amino groups improves the adsorption performance of MOF to CO₂ gas,but the existence of amino groups compresses the pore space of MOF,hinders the transport of reactants or products in the cycloaddition process,and reduces the conversion efficiency of cycloaddition.（3）A new complex[Co（Htzbt）（H₂O）]_n（JY-1）,was successfully prepared by using 2-（1H-1,2,4-triazol-1-yl）benzene-1,3,5-tricarboxylic acid（H₃tzbt）single ligand,and then two complexes[Co（Htzbt）（bpy）]_n（JY-2）and[Ni（Htzbt）（bpy）]_n（JY-3）with the same structure were prepared by introducing 4,4’-Bipyridine（bpy）.The{[Co₃（tzbt）₂（H₂O）₄]（H₂O）₂}_n（JY-4）,was successfully prepared by replacing4,4’-Bipyridine（bpy）with 1,4-di（pyridin-4-yl）benzene（bpb）.Their catalysis in carbon dioxide cycloaddition reaction of epoxides and hydrogenation reduction of p-nitrophenol were explored.Among them,JY-2 showed good catalytic performance for epoxide cycloaddition reaction,and JY-1 showed good catalytic activity for p-nitrophenol hydrogenation reduction reaction.