Construction And Properties Of Coordination Polymers Based On Triazole-pyridine Carboxylic Acid/Flexible Benzimidazole Dicarboxylic Acid

Metal-organic Frameworks（MOFs）is a new type of porous crystalline materials,which are self-assembled by metal units and organic ligands with multiple coordination points through coordination bonds.The construction process of MOFs is influenced by many factors,such as metal ions,structure types of organic ligands,temperature,pH and so on.,and the selection of ligand is particularly important.The rigid heterocyclic carboxylic acids and benzimidazole carboxylic acid ligands show diverse coordination patterns with varied coordination sites.It can be used as bifunctional organic ligands to construct MOFs with stable structures and excellent properties of adsorption/separation,catalysis,fluorescence sensing,magnetic properties and so on.In addition,in order to expand the application prospects of MOFs,we can use other technical means,such as electrostatic spinning technology can be used to develop new and practical applications of composite materials,which will become a hot spot in the field of MOFs research.Based on the above research strategies,the organic ligands:2-（triazole-1-yl）isonicotinic acid（HL1）,5-（triazole-1-yl）nicotinicacid（HL2）,1,4-di（5,6-dicarboxylbenzimidazole-1-ylmethyl）benzene（H₄L3）andthesecondligands:1,3,5-benzenetricarboxylic acid（H₃btc）and terephthalic acid（p-H₂bdc）were selected.Fourteen complexes with different structures and properties were synthesized by hydrothermal method,namely,[Cd（L1）₂（H₂O）₂]_n（1）,{[Cd₂（L1）（btc）（H₂O）₂]·H₂O}_n（2）,[Zn（L1）₂（H₂O）₄]_n（3）,[Co（L1）₂（H₂O）₄]_n（4）,[Ni（L1）₂（H₂O）₄]_n（5）,[Zn（L2）₂（H₂O）₄]_n（6）,[Zn₂（L2）（btc）（H₂O）₂]_n（7）,{[Zn（L2）（p-bdc）_0.5（H₂O）]·（p-H₂bdc）_0.5}_n（8）,[Pb（L2）（H₂O）₂（NO₃）]_n（9）,[Pb（L2）₂（H₂O）]_n（10）,[Cd_1.5（L2）₂（H₂O）（NO₃）]_n（11）,[Cd（L2）₂（H₂O）₂]_n（12）,{[Cd₂（L3）（NMP）（H₂O）₂]·2H₂O}_n（13）and{[Zn（L3）_0.5（H₂O）]·NMP·H₂O}_n（14）.The full paper consists of five chapters:Chapter 1,the basic concepts,synthesis methods,structures and applications of coordination polymers are introduced in detail.Finally,we give a detailed introduction of the significance of this paper.Chapter 2,the structure and basic properties of five coordination polymers based on HL1 ligands were introduced,and the fluorescence properties of complexes 1-3 were investigated.The magnetic properties of complexes 4 and 5 were also studied.Chapter 3,The structure and basic properties of seven novel coordination polymers（Zn（II）、Cd（II）、Pb（II））constructed by hydrothermal method with HL2 as the first ligand and two different second ligands,namely,H₃btc and p-H₂bdctc were introduced in detail.Because of the stable fluorescence properties of complex 12,the fluorescence sensing properties of complex 12 have been tested and studied.The results show that 12 has a high selectivity and sensitivity with low detection limit for CrO₄^2-,Cr₂O₇^2-和MnO₄^-ions in aqueous solution.Chapter 4,two novel complexes were synthesized by using H₄L3 ligands with metal Zn（II）and Cd（II）.The adsorption properties of complex 13 and 14 were tested and studied.At 298 K,the adsorption capacity of 14 for CO₂ was 2.2 mmol g^-1（9.5 wt%）and the mixture of CO₂/CH₄（50:50）show a better selective separation effect.Chapter 5,the preparation of MOF-5 composite thin films by electrospinning was explored,and the SEM characterization of the films was carried out.The results of the experiment are analyzed in detail,and we also had made a plan for the next step.