The Studies Of Metal Organic Frameworks Based On 5-(4-pyridyl)-tetrazolate With Efficient Fluorescence Detection

In recent years,metal-organic frameworks?MOFs?have attracted much attention because of their interesting structures and novel applications.Among of them,the application of MOFs in chemical sensing has become a hot topic among chemists and material scientists.However,the design and synthesis of MOFs with high stability,which can detect metal ions by fluorescence enhancement,is still a challenge.In this paper,we used 5-?4-pyridinyl?-1H-tetrazolium?4-Hptz?with multiple nitrogen ligands as the main ligand,and 1,4-naphthalic acid?NDC?and m-phthalic acid?IPA?were used as the auxiliary ligands,respectilvly.By tuning the metal salts and solvents,three new complexes?1-3?with different structures were successfully obtained.The effects of different metal salts,ligands,and solvents on the structure of the target complexes were investigated in detail.At the same time,we examined the stability of the complexes and explored its application in metal ion sensing.This paper mainly includes the following two works:?1?Under solvothermal conditions,a compound [Cd₄?NDC?₃?4-Hptz?₂?H₂O?₂]·H₂O?1?was prepared by reacting 4-Hptz and NDC ligands with cadmium nitrate as metal salt,methanol and water as solvent.Compound 1 is firstly connected by ligand 4-Hptz and Cd²⁺ to form two-dimensional?2D?layered structure,and then the 2D layers are connected by NDC ligand to form three-dimensional structure.Compound 1 has excellent water stability,thermal stability,and acid-base stability,which are rare among MOFs.At the same time,compound 1 shows excellent fluorescence sensing properties.It can detect Cr³⁺ in water by turn-on fluorescence,which is the first known case.?2?On the basis of the above work,we successfully prepared the compound [Zn?H-4ptz?H₂O]?2?by using IPA instead of NDC as the carboxylic acid auxiliary ligand.In compound 2,it forms a 2D layered structure with the shape of "sea wave" by connecting the 1D chain with the ligand.On the basis of compound 2,we changed the reaction conditions and obtained the compound [Zn₃?H-4ptz?₂?IPA?₂]?3?by hydrothermal method.In compound 3,the [Zn₃N₈?CO₂?₄] secondary building units were connected by two types of ligands to form a pulp-wheel three-dimensional structure.Fluorescence sensing studies have shown that compound 2 can detect Cu²⁺ in water,and compound 3 can detect Cd²⁺ by fluorescence enhancement in water.