Construction Of Yb₆-MOFs And Post-synthetic Functionalized Derived Materials And Their Catalytic Properties Of CO₂ Cycloaddition

Metal-organic frameworks（MOFs）exhibit effective catalytic properties in the preparation of cyclic carbonates through cycloaddition reactions by immobilizing CO₂ due to their high porosity,easy adjustment of structure and function,and potential Lewis acidic sites at metal nodes in the structure.In the design process of MOFs,the size of organic ligands and the types of functional groups connected by ligands are key factors that make them possess different characteristics and functions.In this thesis,a series of hexanuclear Yb cluster-based MOFs were prepared under solvothermal conditions using four organic ligands with different sizes and functional groups,,and further post-synthesis functionalized with iodoalkane.The effects of different structures and functionalization characteristics on the catalytic activity of CO₂ cycloaddition reactions were systematically studied.This work is divided into 3 parts:In the first part,two linear dicarboxylic acid ligands,terephthalic acid（H₂BDC）and 2-amino-terephthalic acid（H₂BDC-NH₂）,were used to synthesize two kinds of hexanuclear Yb cluster-based MOFs materials,Yb-BDC and Yb-BDC-NH₂,by solvothermal method,and the influence of-NH₂ group on the catalytic performance of CO₂ cycloaddition reaction was explored.It was found that the Lewis basic group-NH₂ hanging in the Yb-BDC-NH₂ pore can increase the adsorption capacity of CO₂,and effectively improve the catalytic performance of CO₂cycloaddition reaction.In the second part,two kinds of hexanuclear Yb cluster-based MOFs,Yb-BPDC and Yb-BPDC-NH₂,were prepared by solvothermal method using linear dicarboxylic acid ligands containing two benzene rings,4,4-biphenyl dicarboxylic acid（H₂BPDC）and 2-amino-4,4-biphenyl dicarboxylic acid（H₂BPDC-NH₂）.The catalytic CO₂ cycloaddition activity of Yb-BDC and Yb-BDC-NH₂ was compared respectively to study the influence of catalyst pore size on catalytic performance.The experimental results show that the epoxides show a higher conversion rate under the catalysis of Yb-BPDC and Yb-BPDC-NH₂ with larger pore size.In the third part,the Yb-BDC-NH₂ was post-synthesis functionalized with CH₃I,CH₃CH₂I and C₄H₉I to obtain a series of derived materials,Yb-BDC-CH₃I,Yb-BDC-CH₃CH₂I,Yb-BDC-C₄H₉I.The catalytic properties of these post-synthesis functionalized derived materials for CO₂cycloaddition were further studied.Because I^-will carry out nucleophilic attack onβ-C in epoxide and accelerate the ring-opening process,therefore,the post-synthesis functionalized materials show better catalytic activity.