Design And Synthesis Of Polynuclear Metal Cluster-based MOF Materials For Gas Separation

Metal-organic frameworks(MOFs)have huge application prospects due to their unique structural characteristics.The related fields mainly include fluorescence,catalysis,gas storage,gas separation,sensing,biomedicine,electricity,etc.Among these applications,the application of MOFs in gas separation is a hot topic.According to relevant literature reports,when improving the gas separation performance of MOFs,researchers often use strategies:introducing metal active sites,introducing guest active sites,and introducing ligand active sites.In this thesis,we mainly build polynuclear metal cluster-based MOFs to achieve effective separation of gases.In this work,NbU-1,NbU-2 and NbU-3 materials were successfully prepared,and the crystal structure was characterized by single-crystal X-ray diffraction analysis.Infrared analysis,powder X-ray diffraction analysis,and thermogravimetric analysis were used to perform basic characterization.The adsorption and separation performance of the mixed gas is studied by using gas adsorption device and gas breakthrough device.The thesis is divided into five chapters,which are summarized as follows:The first chapter is the introduction.It systematically introduces the metal-organic frameworks and its application in gas adsorption separation,which leads to the basis and significance of the topic.The second chapter introduces the preparation method of NbU-1 and its properties.Currently,one of the problems plaguing the chemical industry is the efficient and cost-effective separation of C2 hydrocarbons.In order to solve this problem,we synthesized a new material,NbU-1,which has cost-effective raw material,good structure and gas separation properties:the special structural characteristics(planar,mixed-valence copper clusters and Lewis-basic adsorption channels)enable it to interact with acetylene molecules,which results in the highest kinetic separation efficiency of C₂H₂/C₂H₄.DFT-D calculations show that C₂H₂ molecules were adsorbed on two adjacent Cu(I)centers instead of a single open metal site of Cu centers.This result not only provides information for in-depth study of the separation mechanism,but also provides a strategy for the preparation of cost-effective materials that can efficiently separate light hydrocarbons.The third chapter introduces the preparation method of NbU-2 and its properties.We reported a new type of noninterpenetrated and enneanuclear bimetallic cluster-based MOFs,NbU-2,which was synthesized by step-by-step synthesis process.Results showed that the hydrolysis of metal ions is controllable in this step-by-step synthesis process,and this research also provided a new method for the synthesis of polynuclear metal clusters-based MOFs.At the same time,it was found that the activated compound exhibits higher CO₂/N₂ selectivity through testing,which was proved by gas breakthrough experiments of CO₂/N₂ mixture.The fourth chapter introduces the preparation method of NbU-3 and its properties.By post-functional modification methods,a series of heterometallic NbU-3-Mn/M^III compounds were synthesized by exchanging M^III(M^III=V,Cr,Fe)with the pentanuclear Mn^II-based NbU-3-Mn to improve the gas separation performance.Through experimental performance characterization,NbU-3-Mn Fe has similar C₂H₂/CO₂ separation selectivity as NbU-3-Mn,but gas breakthrough experiments demonstrated that NbU-3-Mn Fe has enhanced dynamics separation performance of C₂H₂/CO₂.Chapter 5 is the conclusion and prospect.Summarizes the research work of the full text and prospect the future development of polynuclear metal cluster-based MOF materials.