Fabrication And Property Studies Of Coordination Polymers Based On Polycarboxyl Acid Ligands Containing Oxamic Acid And Ether-O Groups

Coordination polymers（CPs）refer to structurally ordered and infinitely extendable compounds formed by metal ions/metal ion clusters with empty orbitals and self-assembled organic ligands via coordination bonds.Due to the rich structures and wide application value,the synthesis and functional researchs of CPs have been highly sought after by researchers.The modification of ligands to improve the function of CPs has always been a hot topic in coordination chemistry research.In this dissertation,we designed and synthesized two ligands containing oxamic acid groups,N,N′-5-carboxyl-1,3-phenylenebis（ethyl oxamate）（HEt₂L）and 5-（ethyl oxamate）-isophthalic acid（H₂EtL）,and a ligand 5,5′-oxyisophthalic acid（H₄L）containing an ether O group.Under solvothermal condition,these ligands reacted with transition metal ions,alkaline earth metal ions and rare earth metal ions to form nine new CPs,which were analyzed by X-ray single crystal diffraction,powder X-ray diffraction（PXRD）,infrared spectroscopy（IR）,elemental analysis（EA）and thermogravimetric analysis（TGA）to study the structure and thermal stability.For the different structures and the metal center types of CPs,the fluorescence,sensing,adsorption and catalytic properties have been studied.This dissertation is divided into four parts:（1）The concept,construction method and current research progress of coordination compounds are introduced,and examples are given for their different application prospects.In addition,the research background and the significance of the topic of this thesis are expounded.（2）Four different three-dimensional（3D）CPs were constructed by in situ hydrolysis of ligand using HEt₂L ligand with different Mn²⁺and Cd²⁺salts under solvothermal condition:[Mn_1.5L（H₂O）₂]·H₂O（1）,[Mn₂L（C₂O₄）_0.5（NMP）（H₂O）]·NMP（2）,[Cd_1.5L（H₂O）_2.5]·H₂O（3）and[Cd₂L（C₂O₄）_0.5（H₂O）₃]·H₂O（4）.Among them,the ligand L is formed by in situ hydrolysis of HEt₂L.In CPs 1-4,the two oxamic acid groups in L exhibit different syn-syn and syn-trans configurations,showing four coordination modes,resulting in four different novel topologies in four CPs.1 contains an interesting one-dimensional（1D）metal-oxalyl-based zigzag chain;2 contains a 1D channel with a porosity of 52.5%;3 contains a firstly discovered Cd-oxamate layer;4 contains a novel Cd-oxamate-oxalate chain.In addition,1 and 2 show antiferromagnetic interactions,and 3 and 4 have solid-state fluorescence properties.（3）Two different 3D CPs[Ca_1.5L（H₂O）₃]·H₂O（5）,[Sr_0.5（H₂L）]（6）were constructed by using H₂EtL ligand and two alkaline earth metal ions Ca²⁺and Sr²⁺under solvothermal condition,using the similar above in situ hydrolysis method of ligand.Among them,H₂EtL is hydrolyzed in situ to form L and H₂L,respectively.5 and 6 show three-dimensional coordination framework structures.In addition,the solid-state fluorescence properties of 5and 6 were studied,and 5 has fluorescent sensing toward Fe³⁺ions with good selectivity and sensitivity.（4）Under solvothermal condition,H₄L ligand reacted with three different rare earth metal ions Eu³⁺,Gd³⁺and Tb³⁺to form three isomorphic 3D CPs containg 1D channels:H[LnL（H₂O）]·2H₂O(Ln=Eu³⁺（7）,Gd³⁺（8）,Tb³⁺（9）),in which 7 and 9 show strong typical red and green emission,respectively.A series of two-color doped Eu_xTb_1-x-x CPs were prepared by doping different concentrations of Eu³⁺and Tb³⁺ions,and the luminescent colors display the continuous changes from green,yellow,orange to red.In addition,7 has good adsorption property for CO₂,and also exhibits better selective catalytic conversion activity and recyclability for CO₂ and different epoxides at room temperature.