Synthesis And Properties Of Luminescent Porous Coordination Polymers Based On Azobenzenetetracarboxylate Ligand

Porous coordination polymers(PCPs)or metal-organic frameworks(MOFs)have been paid much attention since their great applications in gas adsorption,fluorescence sensors,separation and catalysis.The organic linkers play an important role im the construction of the MOFs.3,3,5,5-azobenzenetetracarboxylic acid(H4L),which has a large conjugated system and an azo functional group as well as the four carboxyl groups,is a good candidate for construction of different MOFs.In this paper,H4L was chosen to construct novel MOFs,and finally a series of transition metal MOFs were successfully synthesized through controlling the reaction conditions.The fluorescence,chemical sensing and I2 capture properties have been investigated.The thesis is divided into four chapters:The first chapter is the introduction,introducing the concept of complexes,the application of carboxylate complexes in fluorescence and adsorption properties,the reported studies of MOFs based on 3,3,5,5-azobenzenetetracarboxylic acid and the basis of the research and the main achievements in this thesis.In the second chapter,thirteen transition metal complexes were successfully synthesized through controlling the reaction temperature,the ratio of the reactants,the pH of the reaction system,the type of anion and so on.The optimal conditions and influencing factors for the synthesis of these complexes are discussed in detail.The third chapter mainly studies the crystal structures of the synthesized porous complex and analyzes the coordination mode of the ligand in the complex.The molecular formulas of the complexes obtained by single crystal structure analysis are:[NH2(CH3)2][Co1.5(μ8-L)]·H2O(1),[NH2(CH3)2][Co0.5(DMF)3][CO6(h(μ3-OH)2(μ8-L)3(H2O)6]·0.5(NH(CH3)2)·H2O(2),[Co4(μ6-L)(μ8-L)(DMF)5]·4DMF(3),[Co2(μ3-OH)(μ8-L)0.5(μ2-H2L)0.5(DMF)(H2O)3]·0.5DMF.2H20(4),[Co2(μ8-L)(H2O)3](5),[Co(μ4-H2L)(DMF)2](6),[NH2(CH3)2]2[Co8(μ3-OH)4(μ4-L)2(μ4-HL)2(H2O)20]·4H2O(7),[Co(μ2-H2L)(H2O)3]· 5H2O(8),[Co(μ2-H2L)(phen)(H2O)2]·H20(9),[Zn4(μ7-L)2(phen)2(H2O)2]·2.5DMF·4H2O(10),[Zn(μ6-L)0.5(2,2’-bpy)](11),[Cd2(μ7-L)(phen)(H20)]·2DMF·2H2O(12),[Cd6(μ6-L)6(DMF)4(H20)11](13).Complexes 1-6 are three-dimensional cobalt(Ⅱ)MOF with one-dimensional channels.The pore shapes and sizes of the six MOFs varies due to the different coordination modes of metal ions and ligands as well as the guests.Complexes 7-9 are zero-dimensional or one-dimensional cobalt(Ⅱ)complexes,which further to form three-dimensional supramolecular structure by π-π stacking or hydrogen bonding.Complexes 10-13 are d10 metal complexes including one-,two-and three-dimensional structures.In complexes 1-13,H4L ligands are fully or partly deprotonated and exhibit various coordination modes such as μ2-,μ4-,μ6-,μ7-,and μ8-,indicating it can be an excellent ligand for constructing MOFsIn the fourth chapter,the thermal stability,fluorescence properties,solvent molecular sensing and iodine capture properties of the synthesized porous complexes are investigated.All complexes 1-13 exhibit emission band centered at 375nm.,which can be attributed to π*→n orπ*→π transitions of the ligand H4L.Complex 1 can keep its framework in common organic solvents such as methanol,ethanol,DMF,acetonitrile,THF and DMA.The solid state fluorescence after immersion in the organic solvents and the suspicion fluorescence in the solvents are further studied,respectively.Studies show that complex 1 exhibits a specific fluorescence enhancing effect by acetonitrile molecules,whether in solid or in solution.Anti-interference and reproducibility experiments show that 1 has good anti-interference and recyclability in the mixed systems.Considering the three-dimensional MOFs 1-5 and 10,this chapter also studies their iodine capture properties.It shows that complex 10 has the highest adsorption amount and the fastest adsorption rate,indicating its potential application in iodine capture.