Synthesis And Properties Of Metal-Organic Frameworks Based On Semi-rigid Carboxylic Ligand

As one kind of porous functional crystalline materials with regular topological structure formed by self-assembly of inorganic units?metal ions metal clusters?and organic ligands,metal-organic frameworks?MOFs?has been widely used in the fields of gas adsorption and separation,chemical sensing,optical materials,catalysis and so on.The structures of MOFs determine their performance,thus the diversity of MOFs structure provides the foundation for its functional investigation.The configurations of MOFs can be designed through the adoption of suitable inorganic units and organic ligand with specific geometries.Therefore,a semi-rigid nitrogen-containing carboxylic ligand 5-[bis?4-carboxybenzyl?amino]isophthalic acid?H₄L?was selected to synthesize four novel MOFs under different conditions.Their structures are characterized,and their performance in sensing and catalysis is studied.The main content of this thesis are as follows:1.Two heteronuclear MOFs?CoLi?HL?-4DMA,HNU-23 and CoLi₂L?DMF?₂,HNU-24?were synthesized with metal ions Li+ and Co²⁺ using H₄L as ligand under solvothermal conditions.The coordination modes of H₄L were discussed,and the different structures of metal clusters induced by different organic solvents were also presented.When DMA was adopted,the metal cluster in HNU-23 was a Co₂LLi₂ tetranuclear metal clusters,and HNU-24 featured Co₂Li₄ metal clusters as DMF was applied.In addition,the sensing properties of HNU-23 and HNU-24 were explored,and the results showed that HNU-23 and HNU-24 can be used as the H+concentration sensor.HNU-23 shows a high linear response of H+ concentration in the range of 0.02-0.2 M;HNU-24 exhibits a similar linear response to H+concentration between 0.1-0.2 M.2.The catalytic properties of HNU-23 and HNU-24 for the degradation of methylene blue?MB?in the absence of light were studied.It is worth noting that Co²⁺in both MOFs adopts tetrahedral coordination configuration,and the content in the complexes is different.The effects of Co2+content,catalyst and H₂O₂ concentration on catalytic performance were discussed.HNU-23 with higher Co²⁺content had better catalytic efficiency than HNU-24.The catalytic efficiency increased with the increasement of catalyst and H₂O₂ concentration,and the influence of catalyst concentration is stronger than that of H₂O₂.3.Through mix-ligands strategy,two different 4-connected 3D metal-organic zeolites?MOZs?,{[Zn₂?L??tta?₂]·3H₂O·DMF·2Me₂NH₂⁺}?HNU-25?and{[Zn₂?L??Mtz?2]·4H₂O DMF·2Me₂NH²⁺}?HNU-26?were synthesized by using H₄L as the main ligand,together with the auxiliary ligands(1H-tetrazole?1H-tta?or 5-methyl-1H-tertazole?1H-mtz?and Zn?CH₃COO?₂ under the similar solvothermal condition.Both MOZs contain uncoordinated N and O atom,which can be served as Lewis base sites.They can be used as "antenna" to coordinate with Ln³⁺ions to sensitize the luminescence of lanthanide ions.HNU-25 can selectively sensing of Tb³⁺and Dy³⁺ ions through sensitized luminescence with detection limits of 3×10^-11 M and 1.1 ×10^-5 M?respectively.The detection limit of HNU-26 for Tb!³⁺ion was 2x10^-9 M.