Stable Metal-Organic Framework:Design,Synthesis,Optical And Electrical Properties

The metal-organic frameworks?MOFs?has rich functions,and exhibits excellent properties in the fields of conductivity,gas adsorption and separation,catalysis,and luminescence,etc.It has received great attention and shown great application prospects in the field of materials science,because its function can be designed,easily modified,and has a large pore volume and specific surface area.However,there are certain practical bottlenecks in the MOFs,and chemical stability is the main factor restricting its application and development.Therefore,it is imperative to design and synthesize metal organic framework materials with good stability and excellent properties.Based on in-depth research on the literature,we designed and synthesized polyalkynyl rigid pyrazole ligands Pz-hexyne,sulfonic acid-functionalized carboxylic acid aromatic ligands H₂BSDC,and thioether-functionalized carboxylic acid aromatic ligands H₂BEDBD,respectively.Furthermore,MOF materials with different functions were synthesized by the coordination of different metal ions,and their basic characterization and performance research were performed.The specific research contents are as follows:First of all,we introduced the research background of the topic selection and mainly presented the characteristics and constraints of the metal organic framework,and finally explains the significance of the topic selection and the research content of this paper.Next,a polyalkynyl rigid pyrazole ligand Pz-hexyne was designed and synthesized.Based on the theory of soft and hard acids and bases,the Ni8 core cluster MOF Pz-Ni-hexyne with 12-linked coordination was synthesized by coordination with metal Ni?II?with excellent stability.Subsequently,imidazole molecules were introduced into its pores by gas-phase diffusion method,X-ray powder diffractometer,infrared spectrometer,ultraviolet spectrometer,scanning electron microscope,and adsorption apparatus were used to prove the imidazole molecules included.Finally,the proton conductivity was studied at different temperatures and relative humidity.The results showed that the proton conductivity changed greatly imidazole loaded before and after.The proton conductivity of Im@Pz-Ni-hexyne MOF was improved by 3 orders of magnitude when the imidazole molecules were introduced into the pores of Pz-Ni-hexyne,and at 90°C and 90%relative humidity,the proton conductivity is 4.26×10^-5S·cm^-1.Furthermore,it was found that the mechanism of proton conduction also changed,and the activation energy loaded before is0.15 e V,and the proton conduction is the Grottuss mechanism.Loaded after,the activation energy increases by 0.83 e V,which is the Vehicle conduction mechanism.Part three,a sulfonic acid-functionalized carboxylic aromatic organic ligand H₂BSDC was designed and synthesized.Pb-BSDC was synthesized by solvothermal conditions with Pb?NO₃?₂,and its crystal structure was studied in detail.With abundant hydrogen bond interactions among the water molecules,sulfonic groups and carboxylate groups,it makes Pb-BSDC a potential candidate for solid proton-conducting material under humid conditions.Next,The proton conductivity of bulk Pb-BSDC samples and single crystal samples are were studied separately,and the results show that the proton conductivity of single crystals is at least two orders of magnitude higher than that of powder samples.At 90°C and 85%relative humidity,The proton conductivity of single crystals reaches 1.71×10^-4S·cm^-1,and has a lower activation energy of 0.35 e V.Finally,we studied the luminescence properties of Pb-BSDC,which exhibited green light for emission performance under ultraviolet wavelength excitation.Therefore,the synthesized Pb-BSDC is a dual-functional material,and provides a reference for future researchers to develop functional materials with proton conductivity and luminescence characteristics.Finally,a sulfide-functionalized directional carboxylic acid ligand H₂BEDBD was designed and synthesized,and coordinated with the Ln-based metal Eu?III?.Eu-BEDBD MOF was synthesized as a potential white light-emitting basic material,and performed basic characterization.Finally,the luminescence properties were studied.The ligand in the structure has a p-?conjugated system,which has a fluorescence enhancement effect on the central metal europium atom.Eu-BEDBD is excited by blue light at 465 nm,and its maximum emission wavelength is 612 nm.Therefore,Eu-BEDBD is a typical red light emission effect MOF,with potential applications in the field of white light emission.