Synthesis And Properties Of Flexible Zr-based Metal-Organic Frameworks

Metal organic framework materials(MOFs)are porous crystalline materials composed of metal ions(clusters or chains)and organic ligands through coordination bonds.With diverse structures,controlled surface engineering,adjustabled pore size and high surface area,MOFs have been widely explored in various fields including gas storage and separation,catalysis,chemical sensing and so on.However,most reported MOFs are not stable enough and are easily damaged which hinder their applications.Therefore,it is of great significance to synthesize MOFs with high thermal stability and chemical stability.In this thesis,we mainly synthesized a series of new flexible zirconium-based MOFs,with high-thermal stability and chemical stability,and study their applications in gas adsorption and fluorescence sensing.The specific work can be divided into the following two aspects:(1)By designing ligands L1 with P-tert-butylphenyl,L2 with P-methylphenyl,L3with P-bromophenyl and L4 with 2-naphthalene groups,we synthesize a series of new zirconium-based MOFs,Zr-SXU-7,Zr-SXU-8,Zr-SXU-9 and Zr-SXU-10,respectively under solvothermal method.PXRD results of these samples before and after immersing them into gifferent solvents show that they are isostructural and all of them exhibit flexible structures and can be stable not only in 3 M HCl solution but also in p H=11 Na OH solutions.The results of gas adsorption showed that all of them have good gas adsorption selectivities for C₂H₂/CH₄ and CO₂/CH₄,especially at 298K,the selectivity of Zr-SXU-7for C₂H₂/CH₄(50/50)can be as high as 102.27.The high robustness and adsorption selectivities indicated that they have potentials in gas adsorption and separation applications.(2)Through the design of N,N-dimethyl group modified with push-pull electronic effect of the new ligand L5,using solvothermal method to synthesize a kind of new zirconium-based MOFs,Zr-SXU-11,It was found that Zr-SXU-11 also has a flexible structure,high thermal stability and chemical stability,and the frame structure would not be collapsed when immersed in 3M HCl solution and p H=11 Na OH solution.The results of gas adsorption showed that Zr-SXU-11 has good gas adsorption selectivities for C₂H₂/CH₄ and CO₂/CH₄,especially at 298K,the selectivity of Zr-SXU-11 for C₂H₂/CH₄(50/50)can be as high as 111.49.The results show that Zr-SXU-11 has the ability of selective fluorescence detection not only for CHCl₃,but also for Fe³⁺.Therefore,Zr-SXU-11 not only has potential applications in selective gas separation,but also has a good application prospect in fluorescence sensing.