Study On Preparayion Of Metal Organic Framework By Carboxylic Acid And Carboxylic Acid Triazole Ligands And Their Properties

Metal-Organic Frameworks(MOFs)are organic-inorganic hybrid materials with intracellular pores formed by self-assembly of organic ligands and metal ions or metal clusters through coordination bonds under specific conditions.Porosity,large specific surface area and structure,unsaturated metal sites and functional diversity,and has a wide range of applications in the fields of gas adsorption and separation,chemical catalysis and luminescent materials.In this paper,several organic ligands were synthesized,and two organic ligands,namely carboxylic acids and carboxylic acid triazole ligands,were selected,and a series of metal organic frames were synthesized by combining d~100 metal salts,rare earth metal salts and main group metal lead salts as raw materials.The crystal structure was analyzed by single crystal X-ray diffraction(XRD)and the coordination and stereoscopic structure of each crystal were described in detail.In addition,the heterogeneous catalytic activity and photofluorescence properties of Zn-MOF(C3)were studied.Five kinds of organic ligands were synthesized in this paper,including carboxylic acid ligands,triazole ligands and carboxylic acid triazole ligands.Two carboxylic acid-containing ligands,4-dimethylaminopyridine-2,6-dicarboxylic acid and 5-(4H-1,2,4-triazole)isophthalic acid,were selected as raw materials to synthesize the metal-organic framework.For the carboxylic acid ligand4-dimethylaminopyridine-2,6-dicarboxylic acid,the main group metal salt lead perchlorate trihydrate and d~100 metal salt cadmium perchlorate hexahydrate were synthesized by hydrothermal method.The crystals C1and C2 have a two-dimensional structure and a three-dimensional structure,respectively.For carboxylic triazole ligand 5-(4H-1,2,4-triazole)isophthalic acid,d10 metal salt zinc perchlorate hexahydrate,manganese perchlorate hexahydrate,and manganese nitrate Hexahydrate were selected,and synthesized by hydrothermal method with crystals C3,C4,and C5.Among them,C5 is a zero-dimensional complex,and C3 and C4 are two-dimensional structures.The rare earth metal salts rhenium perchlorate hexahydrate,rhenium perchlorate hexahydrate,erbium chloride and lanthanum nitrate hexahydrate were also selected to synthesize crystals C6,C7,C8 and C9 by hydrothermal method,where C8 is Three-dimensional structure,the rest are two-dimensional structures.In the synthesis of the zero-dimensional complex C5,two metal salts were added at the same time,namely d10 metal salt manganese nitrate hexahydrate and rare earth metal salt gadolinium perchlorate hexahydrate,but Gd ion was not involved in the coordination.However,in C6,Gd ions coordinate with the ligand to synthesize a two-dimensional structure.It may be that lithium hydroxide is added to deprotonate the ligand,and oxygen atoms are more likely to coordinate with Gd.The carboxyl group is difficult to coordinate with Gd,and only the Mn ion is coordinated with the triazole nitrogen atom.In addition,we also selected crystal C3 to study the catalytic and fluorescent properties.When C3 encounters CN~-,the fluorescence intensity increases,possibly because CN-interacts with the carboxyl group of the ligand in MOF,which results in an increase in energy transfer between the metal center and the ligand,thereby enhancing fluorescence.Due to this interaction between CN~-and MOF,C3 can be used as a catalyst to catalyze the C-C bond formation reaction(The Knoevenagel condensation reaction).C3 has good catalytic activity for most of the selected substrates.Therefore,C3 has potential application value in detecting anion CN~-and catalyzing Knoevenagel condensation reaction.