Construction And Properties Of Coordination Polymers Based On Thioether Carboxylic Acid Ligands

Metal Organic Frameworks（MOFs）,also known as porous coordination polymer（PCPs）,consisting of inorganic centers（such as monometallic ions,polymetallic clusters or chains,etc.）and organic connectors（such as carboxylic acids,phosphonic acids,pyridine ligands,etc.）periodically arranged and assembled in three-dimensional space.Because of its potential applications in fluorescence sensing,catalysis,gas adsorption,magnetism and so on,it has attracted much attention.The structure and properties of the target complexes are determined by the types of central metal ions and ligands.Lanthanide rare earth ions have excellent optical and magnetic properties because of their unique 4f orbitals.The application of MOFs based on transition metal as catalyst for electrolysis of water has begun to receive attention.In this paper,we first designed and synthesized a new thioether carboxylic acid ligand（5-（（pyridin-4-ylthio）methyl）isophthalic acid）（H₂L）.Then[Ln（HL）L]·H₂O（Ln=Eu（1）;Dy（2））was successfully synthesized by solvothermal reaction with rare earth salts of europium and dysprosium.The crystallographic data show that complexes 1and 2 are Ln-MOFs with the same structure.They show excellent fluorescence and magnetic properties,respectively.Complex 1 has a certain stability in water and is highly selective and sensitive to Cr₂O₇^2-and Fe³⁺,so it can be used as a fluorescent probe.Complex 2 exhibits a slow magnetic relaxation behavior with an energy barrier（ΔUeff）of 54 K.Three complexes[M（HL）₂（H₂O）₂]（M=Co（3）;Co,Fe（4）;Co,Ni（5））were synthesized by ligands and transition metal ions.Complexes 4 and 5 are based on 3 doped bimetallic MOFs.They are a series of stable two-dimensional MOFs.The differences in the performance of the three complexes as OER（Oxygen Evolution Reaction）electrocatalysts are explored.Compared with complexes 3 and 5,complex 4has the best performance.In 0.1 M KOH electrolyte,when the current density is 10mA cm^-2,the overpotential is 355 mV,and the Tafel slope is 49.05 mV dec^-1,which is helpful to the study of bimetallic two-dimensional MOFs as OER catalysts in the future.