Research Of Construction And Properties About Nitrogen-containing Heterocyclic Carbon Dots And Metal-organic Frame Materials

Nitrogen-containing heterocycles are widely used as organic precursors in material design and construction.The long pair electrons on nitrogen atoms have high selectivity for specific ions,which can regulate and improve the performance of materials in ion recognition,adsorption,and separation.As a new functional material,carbon dots have high research value in the field of green nanomaterials due to their low toxicity,good biocompatibility,and chemical stability;Metal-organic frame materials（MOFs）are a class of porous coordination polymers composed of inorganic metal ions/metal clusters and organic ligands through self-assembly.The multiple selectivity,modifiability,and structural diversity of their ligands make MOFs exhibit excellent application potential in gas adsorption/separation,catalysis,fluorescence recognition,and sensing.In this thesis,from the perspective of the design and construction of carbon dot materials and MOFs materials,we explore the application prospects of the two types of materials in metal ion detection and dye adsorption through the design of functional materials containing nitrogen heterocycles and the introduction of functional groups through the functionalization of ligands after synthesis.The specific research content is as follows:The first part studies the construction and properties of carbon dot materials using nitrogen containing heterocyclic organic molecules.The design selected 4,4’-bipyridine as the raw material to synthesize a carbon dots material with no functional groups on the surface.By studying the structural characteristics,luminescence characteristics,and the selection of the optimal luminescence intensity conditions of the carbon dot material,the effects of the carbon dot material on the response to different heavy metal ions and concentrations and p H in the sewage system were tested.The research results show that carbon dot materials have specific selectivity for Fe³⁺,and the one-way detection effect is not affected by the sewage system,exhibiting good sensitivity.The detection range of Fe³⁺concentration is 1.0×10^-8～1.0×10² mol·L^-1 with a detection limit of 1.0×10^-8 mol·L^-1。The research results show that carbon dots as Lewis bases have a good response to heavy metal ions Fe³⁺and can maintain good stability in sewage systems.Studies have found that the PSO and PFO models show better coincidences for dye adsorption dynamic data modeling.The second part studies the T-MOF based on the tendon ligand.Through the design of3,6-two（4-pyridine）-1,2,4,5-tetrazine（dpzt）ligand transformed into a pyrazine structure,a three-dimensional rigid MOF material with a new type of structure is built.The study of this T-MOF with good phase purity and thermal stability performance for different sizes of dye molecular adsorption performance.The test results show that T-MOF has certain The maximum adsorption/separation performance is 0.211 mg·g^-1 and the removal rate of MB sub-adult blue is 41.3%and has good adsorption cyclicability.In the third part,F-MOF was constructed using the tetrazine ligand 3,6-bis（4-pyridyl）-1,2,4,5-tetrazine（dptz）,the ligand 4-（4-carboxybenzamide）benzoic acid,and the inorganic metal center Cd²⁺;Through the functional design of tetrazine derivatives（Diels Alder reaction occurring on the tetrazine structure）,the material structure and adsorption effect are regulated.Among them,Nor-F-MOF obtained by modifying the substrate with norbornene successfully achieved fine tuning of the pore size and pore environment of MOF,optimizing the adsorption performance of dye molecules.The test results show that F-MOF with good phase purity and thermal stability has a unique adsorption performance for coumarin（CM⁰）.At a concentration of 1 mg·L^-1,the maximum adsorption amount of coumarin is 0.292 mg·g^-1,and the removal rate of coumarin is 58%;After synthesis,the modified product Nor-F-MOF improved the adsorption effect of the dye coumarin,with a maximum adsorption amount of 0.398 mg·g^-1 and a removal rate of 79.2%for coumarin at a concentration of 1mg·L^-1.The experimental fitting is fitted in the PSO and PFO models and shows good sync.The results show that the introduction of functional groups based on the post synthesis modification strategy can significantly improve the adsorption performance of F-MOF for coumarin.