Synthesis And Properties Of Rigid Aromatic Carboxylic Acid Metal-organic Frameworks (MOFs)

Objective:We designed and synthesized a series of new aromatic mono-,di-,tri-,and tetracarboxylic acid ligands,because of their strong coordination ability,various coordination modes and higher thermal stability.MOFs were synthesized from these new aromatic carboxylic acid ligands and transition metal ions by solvothermal or hydrothermal methods.Subsequently,the properties of MOFs were also studied detailedly,in order to obtain MOFs materials with special properties.Methods:1.Using cheap and available materials,such as halogenated aromatic carboxylic acid,methoxycarbonyl phenylboronic acid,pyridine boronic acid,pinacol ester,diphenylamine and methyl acrylate,as the substrates,new aromatic carboxylic acid ligands were synthesized through various chemical reaction,for example,acylation,esterification,diazotization,bromination,Miyaura boric acid esterification,Buchward-Hartwig,Heck,Suzuki coupling and hydrolysis.The target compounds and intermediates were characterized by 1H NMR,13 C NMR,HRMS and single-crystal X-ray diffraction.2.MOFs were synthesized from aromatic carboxylic acids and transition metal by hydrothermal or solvothermal reaction,by the means of adjusting the solvent,temperature,pH,reaction time and the ratio of metal ion-carboxylic acid ligand.And their structures were confirmed by single crystal X-ray diffraction,elemental analysis,IR.The BET and pore size of MOFs were calculated by N₂ adsorption/desorption experiments.The thermal stability and purity of the crystal were investigated by TGA and PXRD,respectively.The fluorescence properties of the materials were investigated by fluorescence spectrophotometer.3.The activated MOFs was obtained by ion exchange,and its catalytic cycle times,stability and metal loss were investigated.Results:Nineteen new mono-,di-,tri-,and tetracarboxylic acid compounds were synthesized in high yield,and their structures were characterized by 1H NMR,13 C NMR and HRMS,single crystal,respectively.We have used these ligands to react with transition metal ions to generate seven new compounds,namely,{[Co?L?₂]·2H₂O }?????HL = 4-?4-pyridyl?-naphthoic acid,{[Ni?L?₂] ·DMA }?????HL = 4-?4-pyridyl?-naphthoic acid?,{[Co?L?₂] ·2H₂O }?????HL = 6-?3-pyridyl?-2-naphthoic acid?,{Cd?L?₂}?????HL = 6-?3-pyridyl?-2-naphthoic acid?,{Zn?L?}?????L = 2,5-bi?1-H-imidazole?terephthalic acid?;[Cd₃?L?₂?L'??L''?]?????H₂L = 4,4'-?9,10-anthracenediyl?dibenzoic acid?,L'=3-picolinic acid;L''=4-picolinic acid?;{Me₂NH₂[In?L?]·?DMF?}?????L = 3,3',5,5'-tetracarboxylic acid biphenyl?,which structures were characterized by IR spectroscopy,elemental analysis,thermogravimetric analysis and single-crystal X-ray diffraction.The experiments on the compound VI show that when excited at 325 nm wavelength,complex ? exhibits intriguing fluorescent properties with the strongest emission at 450 nm.Using Cu²⁺ exchange Me₂NH²⁺ of ?,Cu²⁺@? was obtained.Cu²⁺@? can effectively catalyze three component click reaction including alkynes and alkyl halides and sodium azide,the catalyst can be reused and the structure remains the same.Conclusion:The synthetic methods based on aromatic carboxylic acid were constructed through reasonable design.At the same time,seven MOFs were synthesized by the reaction with synthetic ligands and different metal ions.The experiments show that compound ? exhibited luminescence properties,and Cu²⁺@? can catalyze three component reaction with alkyne and triazole.The use of extended ligands not only can synthesize large pore channels and MOFs with high specific surface area,but also can successfully obtain multifunctional materials with special catalytic behavior.The synthesis method from ligand to MOFs is feasible,since the inadequate number of MOFs,the synthetic method needs to be improved,and the properties of MOFs needs to be further studied.