Study On The Synthesis,Structure And Fluorescence Properties Of Cluster-based Coordination Polymers Based On Pb And Post 3d Metals

Coordination polymers have received great attention in the field of materials science because of their outstanding properties in gas separation,asymmetric catalysis,nonlinear optics,and ion sensing.It shows a unique advantage in designing crystalline materials with a wide range of characteristics.Although a lot of work has been done in the purposeful design and controllable synthesis of coordination polymers,it is still a huge challenge to synthesize these functional complexes with interesting network structures and properties.Obtaining new coordination polymers depends on a variety of reaction parameters,including metal ions,ligands,pH,solvent,temperature,etc.Here,the structural properties of organic multidentate ligands play an important role in controlling the derivation framework of complex structures and topological structures,and different synthetic methods have emerged as a means of regulation.In most cases,different structures will lead to different functional characteristics.Some fascinating properties of metal clusters can be inherited by the fi nal structure,and metal cluster units containing different terminal positions can not only be used for reasonable assembly,but also create potential active sites for effective adsorption and other chemical/physical activities.point.In particular,lead as the main group heavy metals and post-3 d metals,due to the stereochemical activity of the lone electron pair,the metal ions can form complexes with rich structures ranging from multi-nuclear clusters,1D to 3D coordination polymers.In this paper,linear carboxylic acid ligands containing multi-nitrogen heterocycles,pyridine carboxylic acid linear ligands,and triangular carboxylic acid ligands were selected to synthesize several examples of coordination polymers,and fluorescence and gas adsorption studies were carried out according to different characteristics.And several examples of cluster-based coordination polymers were synthesized by different methods,and the differences in morphology and properties were explored.The main research contents and conclusions are as follows:1.Two cases of inorganic anionic compounds were synthesized that[Pb8(?4-O)2(?3-OCH3)6Cl2][Pb4(?3-OH)4(NO3)8](1)and[Pb4(?3-O)(?3-OCH3)3(NO3)3](2).The structural characterization shows that the asymmetric unit of 1 contains 12 Pb2+ions,each of which is in an extremely complex coordination environment.Through temperature adjustment,although 2 has the same[Pb4O4]cubane building unit as 1,2 is a relatively simple structure,and the asymmetric unit contains only two Pb2+ions.Through the fluorescence test of the two,the former is a single-phase white luminous body,while the latter can be adjusted accurately by changing the intensity of the dual excitation,and the fluorescence lifetime is in the nanosecond range.More intriguingly,although the Pb-MOF could not be generated as expected,the target product could be generated only by adding a certain amount of the organic ligand Hpbica,indicating that the organic linker played an inducing effect,and the compound also provided a rare system to evaluate the binding competition between pyridine-carboxylate organic linker and various inorganic ions such as CH3O-,Cl-,O2-and NO3-for Pb(?).2.Use linear organic ligands such as H2tzba,additional trifluoroacetic acid(TFA)was added as an auxiliary regulator to synthesize[Me2NH2][Ni3(OH)(COO)6N3(H2O)3]·8DMF(3),which is a three-dimensional anionic network structure with a theoretical porosity up to 73.5%.According to its high porosity and frame characteristics,conducted a gas adsorption test.Using a semi-rigid polydentate carboxylic acid ligand such as H3tca,a reported case of[Me2NH2]3[Cu3(C21H12NO6)2(H2O)3]·13CH3OH·4H2O(6)was synthesized.And the synthesis was carried out using microwave-assisted solvothermal,and the advantages of microwave synthesis were demonstrated through the comparison of morphology and performance characterization.Afterwards,based on the introduction of glycolic acid(H2gac)as the second auxiliary compound,{[Me2NH2]2[Cu3(tca)8/3]}·6DMF(4),after changing the temperature and adding 0.1 M 200 ?L HCl,[Cu4(H2O)4(gac)4]·DMF(5),this leads to a coordination competition between a small molecule carboxylic acid and a polycarboxylic acid ligand and the role of the regulator.In addition,different crystals that have been reported are synthesized under microwave.This shows that in different reaction systems,the resulting the reaction priority is different,and the competitive coordination of small molecule carboxylic acid can also be further confirmed.After adding excess small molecule ligand,the priority in microwave is increased.Under the action of microwave,the adjustment of pH can affect the morphology and size of the product.A certain impact;and for the change of temperature and pH in solvothermal synthesis,two different coordination polymers were successfully obtained,which could not be obtained by microwave.Later,based on the high porosity of compounds 3 and 6,the gas adsorption study was carried out due to the replacement of low boiling point solvents.The method causes the frame to be unstable and does not achieve the ideal adsorption effect,and the follow-up will continue to study.3.A porous coordination polymer {[Me2NH2]3[Zn3(pidc)3(DMF)2]}n(7)was synthesized using flexible ligand H3pidc,and then synthesized three Pb,Cd,Co-based metal-organic frameworks(8-10).The 5 mg sample was dissolved in 10 mL of metal ion solution,and a fluorescent suspension of 500 ppm was prepared for metal ion recognition.From the fluorescence spectral emission intensity,it could be seen that Pb-MOF had a general quenching effect on metal cation.Then,specific fluorescence analysis was carried out for Zn-MOF and Cd-MOF.It was found that both Fe3+and Cu2+were quenched obviously by Zn-MOF.Then,by gradually increasing the ion concentration of the suspension,testing and analysis were carried out.From the fluorescence spectra and the linear fitting curve of the quenching,it could be seen that the fluorescence quenching experimental data of Fe3+and Cu2+showed a good linear relationship.However,Cd-MOF only showed a good quenching effect on Fe3+.It can be concluded that the reason of fluorescence quenching is that the frame is excited by cation,generating electron transfer and forming synergistic resonance effect,and the change of intensity is due to charge transition between ligand and metal.At the same time,according to the framework characteristics of Zn-MOF,which can effectively detect binary ions,it provides a good idea for the subsequent design of porous coordination polymers with specific ion recognition performance.