Synthesis,structure And Properties Of Metalorganic Frameworks Based On Fluorenone Pyridine And Tetracarboxylic Acid Ligands

As one of the research hotspots over the past few years,metal-organic frameworks（MOFs）are a class of supermolecular crystalline porous materials.MOF is usually centered on metal ions or clusters to combine a periodic framework with organic ligands.Due to its unique properties such as well-developed porosity,high surface area,tunable pore size and so on,MOFs have been extensively applied in numerous areas,including gas storage and separation,heterogeneous catalysis,magnetism,drug delivery,chemical sensing,etc.In this thesis,we chose 2,7-di（pyridin-4-yl）-9H-fluoren-9-one（L1）,1,1’:4’,1’’-terphenyl-2’,4,4’’,5’-tetracarboxylic acid（H₄L2）and 5,5’-（9,10-anthracenediyl）di-isophthalic acid（H₄L3）as organic ligands to coordinate with transition metal ions or rare earth metal ions,and successfully synthesized nine novel metal-organic complexes by the diffusion method or solvothermal method.The crystal structures,phase purities,thermal stabilities and fluorescence properties of the complexes were characterized by single crystal X-ray diffraction,powder X-ray diffraction,elemental analysis,thermogravimetric analysis,infrared spectroscopy and fluorescence spectra.The main research results of this thesis are summarized as follows:1. Based on L1 and Cd²⁺ion,a 1D coordination polymer[Cd（L1）₂（NO₃）₂（CH₃OH）]_n（1）have been synthesized by diffusion method under ambient conditions.Based on L1,H₄L2 and other metal ions(Zn²⁺,Co²⁺,Ni²⁺),three 1D coordination polymers have been synthesized by the solvothermal method under high temperature and pressure conditions,namely[Zn（L1）（NO₃）（CH₃COO）]_n（2）、[Co（L1）₂（H₂L2）]_n（3）、[Ni（L1）₂（H₂L2）]_n（4）.In the structure of compound 1,adjacent Cd²⁺ions were bridged by L1 ligands to produce a 1D zigzag chain extending along the[1 0 1]direction.In the compound 2,the structure contains dinuclear clusters Zn₂（COO）₂.The clusters are bridged by L1ligands to form a 1D ladder chain extending along the[1 1-1]direction.Single-crystal analyses reveal that compounds 3 and 4 are isostructural.Adjacent Co²⁺or Ni²⁺ions are bridged by L1 and H₄L2ligands to form 1D chains extending along the[7 17 0]direction.Compounds 1 and 2 emit yellow-green light and the emission maximum locate at 545 nm and 538 nm,which originated from the L1.Compounds 3 and 4 are simple paramagnetic compounds with almost negligible interaction between metal ions.2. Based on H₄L3 and rare earth metal ions,five isostructural 3D coordination polymers have been synthesized by the solvothermal method under high temperature and pressure conditions, namely[Ln₂L3（H₂L3）（NMP）₂]·DMF·3H₂O（Ln=La,5;Ce,6;Sm,7;Eu,8;Gd,9）.In these compounds,the structures contain dinuclear clusters Gd₂（COO）₈.The clusters are bridged further across the carboxylic ligands and expended into a 3D framework.The compound 9 displays high structural stability in water with a p H in the range of 2～11.Selective experiments with metal ions indicate that the compound 9 exhibits clearly turn-off quenching response toward UO₂²⁺in aqueous solutions,with the K_sv value calculated to be 4.053×10⁴M^-1（R²=0.99685）in the concentration range of 0～20μM.The detection limit for UO₂²⁺is 1.417μM.In addition,the compound 9 shows remarkable turn-on fluorescence response for selective detection of PO₄^3-in aqueous solutions,with the detection limit calculated to be 1.55μM（R²=0.98715）in the concentration range of 0～35μM.Furthermore,the compound 9 also exhibits significant turn-off quenching response for selective detection of 2-thiothiazolidine-4-carboxylic acid（TTCA）in aqueous solutions with the K_sv value calculated to be 1.766×10⁴M^-1（R²=0.99654）in the concentration range of 0～20μM.The detection limit for TTCA is 3.252μM.The above experimental results show that the compound 9 can act as a multi-response luminescence sensor to detect UO₂²⁺,PO₄^3-and TTCA.The excellent anti-interference performance and recyclability were also verified by experiments.Lastly,the possible detection mechanism of the compound 9 has been discussed in detail.