The Synthesis,Structures And Properties Of Coordination Polymers Based On A S-containing Bithiophene Dicarboxylic Ligand

Porous coordination polymers?PCPs?,also called as metal-organic frameworks?MOFs?,as a kind of burgeoning crystalline porous materials,have rapidly developed into one of the hottest areas in chemistry materials science due to the structural variety and extensive application.As far as we are aware,the carboxylic ligands occupy a large proportion in constructing the coordination polymers,because the oxygen atoms of the carboxyl group have strong affinity to metal ions.Based on this,the dissertation mainly focuses on the design and synthesis of the coordination polymers based on a bithiophene dicarboxylic ligand:on the one hand,compared with monocarboxylic acid,dicarboxylic ligands have stronger coordination ability,flexible coordination models,high stability and larger pore size,etc.On the other hand,thiophene groups incorporated into dicarboxylic ligands,can enhance the conjugation degree of the ligand to endow the frameworks with good rigidity;meanwhile,the soft alkaline sulfur atoms act as high active sites,correspondingly changing the properties of the coordination polymers,like as photoluminescence,adsorption and catalytic performance.Hereby,a series of multifunctional coordinationpolymersweresynthesizedandcharacterizedwitha thiophene-containing ligand,3,4-dimethylthieno[2,3-b]thiophene-2,5-dicarboxylic acid?H₂L?.The primary contents are as follows:A series of alkaline earth coordination polymers,formulated as[MgL?DMF??H₂O?]?1.5DMF?H₂O?1?,[CaL?DMF?]?2?,and[SrL?DMF?]?3?,respectively,were synthesized and characterized systematically under the solvothermal conditions.X-ray single crystal diffraction analyses for these compounds revealed that compounds 1 belongs to monoclinic space group with the two dimensional structure,whereas compounds 2 and 3 pertain to orthorhombic space group and possess 3D frameworks.All the compounds were characterized using powder X-ray diffraction?PXRD?,IR spectroscopy,elemental analyses and thermogravimetric analyses.In addition,the solid-state photoluminescence behaviors for 1-3 were attributed to the ligand emission at room temperature.A coordination polymer of transition metal manganese?II?,with the molecular formula,[Mn?L??DMF?]?4?,which is a three dimensional skeleton containing 1D rhomboid channels after omitting the coordinated DMF molecules,was solvothermally gained.Thermogravimetric analysis and CO₂ adsorption isotherm revealed that it possesses relatively higher stability and porosity.Photocatalysis dye degradation of methylene blue?MB?and methyl orange?MO?consequently revealed that the activated samples showed quite efficient photocatalytic activities toward the MB with high sensitivity and selectivity.Two isostructural lanthanide coordination polymers with 3D porous framework,namely[Ln₂L₃?DEF?₄]?DEF?6H₂O?5-6,Ln=Eu,Tb?,were presented.After activated by removing the guest molecules,they displayed a reversible adsorption isotherms of CO₂,indicating a typical physisorption process of a microporous material.And they possess the excellent capacity to adsorb and separate CO₂/N₂ gas mixture.The solid-state fluorescence in the room temperature showed that they emit the characteristic spectra of Eu and Tb,respectively.Further systematic fluorescent analysis experiments revealed that they are all promising fluorescence probes which are rapidly responsive to recognize nitrobenzene and Fe³⁺by obviously decreasing,even quenching of the fluorescence intensity,along with high sensitivity and favorable recyclability.The possible mechanism of the fluorescence quenching was also discussed.