Synthesis,Structure And Properties Of Coordination Polymers Based On Polycarboxylic Acid Ligands

Coordination polymers（CPs）are compounds in which metal ions or clusters form a network struc-ture with organic ligands through coordination bonds.These compounds have diverse structures and properties.With the continuous development of science and technology,more and more studies have shown that coordination polymers have broad application prospects in chemical sensing,fluorescence detection and other fields.This paper mainly introduces the research progress of coordination poly-mers in chemical sensing and fluorescence detection,including their principles,design and imple-mentation methods,as well as future development directions and challenges.1.A three-dimensional coordination polymer Cd L1·2DMF（1）was prepared by solvothermal method using[1,1’:4’1"-terphenyl]-2,4,4’’,5-tetracarboxylic acid（H₄L1）as organic ligand and transi-tion element Cd²⁺metal salt.The space group of complex 1 is C2/c.In 1,four oxygen atoms from four carboxyl groups of four different ligands form eight-coordinated with Cd²⁺,and form a three-dimensional structure in space through the multi-benzene ring of the ligand.The results of powder diffraction experiments show that 1 is highly matched with the simulated spectrum,and the material phase purity is good.Photoluminescence experiments show that 1 emits purple light.Further photo-luminescence experiments show that 1 can be used to detect Fe³⁺in aqueous solution,and its fluores-cence quenching constant K_sv is 6.8×10⁴ M^-1 when the ion concentration is between 0-100μM.This sensing material has good reusability and strong anti-interference.Finally,the sensing mechanism of complex 1 to Fe³⁺was obtained by UV absorption experiment.2.Cd L2·H₂O（2）with two-dimensional extended structure was prepared by solvothermal method using 9H-carbazole-2,7-dicarboxylic acid（H₂L2）as organic ligand and transition element Cd²⁺metal salt.The asymmetric unit of 2 contains two Cd²⁺ions,one L2^2-ligand and two coordinated water molecules.L2^2-ligands bridge four Cd atoms by connecting two Cd²⁺ions with each carboxyl group.A series of parallel Cd-O-C chains extending along the c-axis are formed between carboxylate and Cd²⁺ions.The carbazole moiety in the L2^2-igand connects these Cd-O-C chains to form a 2D coor-dination network on the ac crystal plane,which is further stacked along the b-axis to construct the crystal structure.The powder diffraction experiments show that complex 2 has high stability and can maintain a good skeleton structure under 60 days of aqueous solution immersion.Fluorescence sens-ing experiments show that complex 2 has strong fluorescence quenching of aztreonam（ATM）in water,and the K_svvalue is 1.12×10⁴M^-1（R²=0.99914）.The selective sensing mechanism of two pairs of ATM was explored by theoretical calculation and fluorescence lifetime test.3.A coordination polymer[Eu₃L2₃（CH₃COO）₂（H₂O）₂（m₃-OH）]×3DMF（3）was synthesized by sol-vothermal reaction of 9H-carbazole-2,7-dicarboxylic acid（H₂L2）ligand with Eu³⁺.The accuracy of the synthesized material was verified by single crystal X-ray diffraction,powder X-ray diffraction,thermogravimetric analysis and fluorescence analysis,and its potential sensing properties were fur-ther studied.Through fluorescence sensing experiments,3 can achieve rapid detection of quercetin（QC）in the concentration range of 0-50μM.It has high selectivity and sensitivity,with a K_sv of7.5×10⁴ M^-1（R²=0.99137）,a detection limit of 1.2×10^-7 M,and good anti-interference ability and recyclability.The main mechanism of fluorescence quenching of QC for 3 was explored by UV ab-sorption experiments.