Construction Of Coordination Polymers With Carboxylate And Azolate Ligands

Metal-organic frameworks（MOFs）usually have ultra-high porosity and large internal surface area,which makes MOF show great potential in field of heterogeneous catalysis,molecular recognition,ion exchange,magnetic,ferroelectric,fluorescence,nonlinear optics,especially in gas adsorption separation and electrocatalysis.In this work,we mainly discuss on ligands with carboxyl groups and azolate groups,and using the respective advantages of the two groups to synthesize a series of new coordination polymers under solvothermal method.The properties of gas adsorption separation and electrocatalysis were tested according to their corresponding structures.The main results are as follows:1.Complexes 1-13 were synthesized with Cu²⁺and lanthanide metals under strong alkaline conditions by using 1H-pyrazole-3,4,5-tricarboxylic acid（L）as bridging ligands.In these structures,Cu²⁺is chelated with the pyrazole nitrogen atoms of the ligand L to form a plane,and then Ln³⁺is coordinated with the carboxyl oxygen atom on the ligand L to form a three-dimensional structure.The ligand L and terephthalic acid（bdc）and its derivatives were further combined to synthesize complexes 1-5 with large pore sizes,and the BET and CO₂ adsorption performance of complexes 1-2 were tested.The abundant N and O binding sites on the ligand L also make it very flexible in coordination with metals.By changing the rare earth metals and the p H of solvents,complexes 6-13 were synthesized.After the transition metal Cu²⁺was replaced with Co²⁺,complex 14 was synthesized,and the phenomenon of chelation also appeared.2.Carboxyl-containing ligand trimesic acid（btc）and polyazole-containing ligand1,2,4-triazole（tz）and its derivatives 2-amino-1,2,4-triazine azole（NH₂-tz）were used to synthesize complexes 15-18.In complex 15-16,the solvent is DMF and water,which causes DMF to decompose formic acid in water.Together with btc and tz,Formate also participates in coordination.It forms a very complex 3D MOF with transition metals Fe²⁺and Co²⁺.The electrocatalytic OER test of complex 16 was performed,and its overpotential was 355 m V,showing relatively good OER catalytic activity.The solvent was changed to acetonitrile and water,and the complex 17 was synthesized.The ligand tz was changed to NH₂-tz to form complex 18.Complex 15-18 demonstrates the flexibility of coordination when carboxyl and polyazole groups are used in combination.