Construction And Property Studies Of Metal-Organic Frameworks Based On Polycarboxylic Acid Ligands Containing Amide/Amino Groups

As a cross product of modern multidisciplinary,metal-organic frameworks(MOFs)have become one of the frontier spots in the field of coordination chemistry.Because of the high porosity of the framework,the designability and modifiability of the structure,MOFs is used in many fields such as materials,biology,medicine,etc.In order to construct high-performance MOFs,how to rationally select metal ions and functionally modify ligands has always been a research hot spot for researchers.Among them,polycarboxylic acid ligands are popular due to their strong coordination ability and rich coordination methods,and with the help of such ligands,a series of classic MOF materials(such as MOF5)have been constructed.In addition,many documents proved that the use of ligand functionalization(amide,amino,pyridine,etc.)to improve the performance of materials has proven to be an effective strategy.Based on the above research and analysis,this paper selects 2-(isonicotinamide)terephthalic acid(H₂L)and 3,3',5,5'-tetracarboxybenzidine(H₄L)as organic ligands,alkaline earth metal ions and transition metal ions are used as metal centers.Three types of MOFs have been constructed by solvothermal methods,and their properties in fluorescence sensing,gas adsorption,and catalytic conversion have been studied.The content of this paper is as follows:(1)Chapter 1:briefly introduce the basic concepts and related research progress of coordination chemistry,coordination compounds,metal-organic framework materials,etc.Then,the synthesis methods of the complexes were introduced.The application status of fluorescence sensing,gas storage and separation,and catalytic conversion are illustrated.This paper comprehensively expounds the topic selection ideas and main research content of this thesis.(2)Chapter 2:a three-dimensional complex with good fluorescence properties,[Zn L(DMA)]·DMA(1),was constructed by using H₂L ligand and transition metal Zn²⁺ions with the d¹⁰electron structure.Through the detection of different kinds of antibiotics in the solution,the complex exhibits a strong recognition function for RDZ(ronidazole),and can be used as a fluorescent probe material for special antibiotic detection.(3)Chapter 3:two isostructural three-dimensional MOFs were constructed using H₂L ligand and Zn²⁺and Cd²⁺ions,respectively,{[Cd₂L₂(H₂O)₂]·4H₂O}_n(2),{[Zn₂L₂(H₂O)₂]·4H₂O}_n(3).Taking Cd-complex 2 as an example,due to good stability and strong fluorescence,this paper uses the complex to detect different kinds of antibiotics in solution.The results show that it exhibits excellent fluorescence recognition performance for both DTZ and RDZ.The material has an effective porosity of 26.5%and the exposed amide groups in the pores,leading to moderate loading for CO₂as well as high adsorption selectivity for CO₂-CH₄mixture.The unsaturated metal ions exposed in the pores are also potential lewis acid catalytic centers,which catalyzed the cycloaddition of CO₂and epoxides to produce the cyclic carbonate products.(4)Chapter 4:choose H₄L ligand and Mg²⁺,Mn²⁺,Co²⁺to construct three isomorphic three-dimensionalMOFs,{[Mg₂L(DMA)(H₂O)₂]·2DMA·H₂O}_n(4),{[Mn₂L(DMF)₂(H₂O)]}_n(5),{[Co₂L(DMA)(H₂O)₂]·2DMA·H₂O}_n(6).Taking complex 4as an example,because of its high effective porosity of 54.2%and the presence of active sites for the uncoordinated basic amino groups in the pores,this paper studies the gas adsorption properties of the complex.The complex can effectively and selectively adsorb CO₂in the mixed gas CO₂-CO and CO₂-CH₄,and especially has a good separation function for the toxic gas CO₂-CO.The unsaturated central metal ion exposed by the channel after solvent removal can effectively catalyze the conversion of CO₂and epoxide through cycloaddition reaction to produce cyclic carbonate products,which is beneficial to the fixation and reuse of CO₂.