Fabrication And Property Of MOFs Based On The Bifunctional Ligands Containing Nitrogen Heterocycle And Carboxylic Acid

Metal-organic framework materials?MOFs?has become one of the most active topics in inorganic chemistry and material chemistry because it has important application prospects in gas adsorption and separation,sensors,drug delivery and delivery,catalytic reactions and other fields.Organic ligands containing azolyl and carboxylic acid bifunctional ligands are one of the representative ligands used to prepare MOF materials,such as imidazole carboxylic acid,triazolyl carboxylic acid,tetrazolium carboxylic acid,pyrazole carboxylic acid and so on,which have been widely used in the assembly of MOFs.Azolyl and carboxylic acid ligands with strong bridge coordination ability are easy to form coordination bonds with a variety of metal ions,therefore,this type of ligands can be used to construct different network structures and achieve different functional characteristics.Based on the above strategies,two ligands containing azolyl and carboxylic acid bifunctional coordination groups were selected,4,6-bis?imidazol-1-yl?isophthalic acid?H₂bizip?and 4,6-bis?triazol-1-yl?isophthalic acid?H₂btzip?,as organic bridging ligands,four complexes with different structures and properties were synthesized by solvothermal method,[Co?bizip??H₂O?_0.5]·H₂O?1?,[Zn?bizip?]?2?,[Mn?bizip??H₂O?₂]·H₂O?3?and[Ni?btzip??H₂btzip?]·2DMF·2H₂O?4?.In the first chapter,the research progress of metal-organic framework materials is introduced firstly,and then the characteristics and different properties of MOFs are described.Finally,the research background of azolyl carboxylic acid ligands and the significance of this thesis are expounded.In the second chapter,three complexes were constructed based on H₂bizip ligands,[Co?bizip??H₂O?_0.5]·H₂O?1?,[Zn?bizip?]?2?and[Mn?bizip??H₂O?₂]·H₂O?3?.Complex 1 has binuclear[Co₂?COO?₄?H₂O??N?₄]clusters as secondary building unit,and a three-dimensional porous network structure was formed by btzip ligand,in which,there is a rhombic one-dimensional channel along the c axis direction with an effective pore size of 4.3×4.3?²and a porosity of 26.7%.The Zn?II?ions in complex 2 are connected into a two-dimensional layered structure by the carboxylic acid group and imidazole N atom in the ligand.Complex 3is a mononuclear molecule.The gas adsorption of complex 1 was studied,it was found that complex 1 had moderate selective adsorption properties for CO₂,the adsorption capacities of CO₂ at 298 and 323 K were 32.2 and 27.9 cm³g^-1,the adsorption capacities of CH₄ were 18.5and 15.7 cm³g^-1,respectively.Meanwhile,at 100 kPa,the corresponding CO₂/CH₄?50:50?selectivities were 2.4 and 2.5,respectively.The fluorescence of complex 2 and the magnetic properties of complex 3 were also studied:2 showed blue purple luminescence,and complex3 showed antiferromagnetic properties.In the third chapter,complex 4 was constructed by solvothermal method using nickel wire and H₂btzip ligand,complex 4 is a binodal?4,6?-connected fsc net,with two-dimensional channels?pore sizes of 5.0×3.2 and 5.9×4.9?²?modified by free-COOH groups and uncoordinated triazo N atoms,which not only makes complex 4 have higher adsorption ability of CO₂ and C₂H₆,but also shows significant adsorption selectivity of CO₂/CH₄,CO₂/CO,and C₂H₆/CH₄.In addition,complex 4 showed good chemical stability in aqueous solution.It was confirmed by Grand Canonical Monte Carlo?GCMC?simulation that complex 4 had multiple CO₂ and C₂H₆ binding sites.Because of the existence of Br?nsted acidic acid-COOH group in the pore channel,the complex exhibits high catalytic activity for cycloaddition reaction of CO₂ with epoxides at 2.0 MPa and 80°C.