Design Synthesis And Applications For CO₂ Fixation Of Copper And Rare Earth-Organic Framework Materials

CO₂ is one of the main causes of greenhouse effect and ocean acidification.Recovery of carbon dioxide by carbon capture and utilization（CCU）technology to produce valuable chemicals has a good industrial prospect,and it is also an effective method to solve the problem of global warming and achieve sustainable development.Due to the low reactivity of CO₂,catalysts are needed to realize the chemical conversion of CO₂.Compared with traditional catalytic materials,metal-organic framework materials（MOFs）have attracted much attention and praise because of their high specific surface area and modular properties.In this paper,dinuclear,pentanuclear copper cluster MOFs and hexanuclear rare earth cluster-based MOFs were designed and synthesized by solvothermal method.Their structures and morphologies were investigated by elemental analysis,infrared spectroscopy,X-ray single crystal diffraction,X-ray powder diffraction,gas adsorption,scanning electron microscopy etc.,and then their catalytic performances for the cycloaddition reaction of carbon dioxide and epoxides were evaluated.The full text is divided into five chapters:In the first chapter,the structural characteristics and synthesis methods of metal-organic framework（MOFs）materials are briefly introduced,and the achievements of MOFs materials in catalyzing the cycloaddition reaction of CO₂ and epoxides are summarized.In chapter 2,the transition metal copper ions and the semi-rigid tripod organic ligand 2,4,6-tris（3-carboxyphenoxy）-1,3,5-triazine were selected to synthesize the binuclear copper cluster-based cage MOFs materials by solvothermal method.The molecular formula is[Cu₁₂（TCPT）₈（H₂O）₆（DMF）₆]?x S（1）.Eight tripod ligands TCPT are connected with six paddle wheels[Cu₂O₂（COO）₄]secondary structural units to form a discrete cage structure with cavity diameter of 15.36?and a window size of11.33?×6.04?.The 3D supramolecular framework is formed by intermolecular hydrogen bonding andπ-πstacking between cages.PLATON shows that the porosity of complex 1 is 44.4%.The complex has good chemical stability and thermal stability.After structural analysis,copper ions coordinate with TCPT ligand,DMF and water,and can be used as Lewis acidic sites to catalyze the cycloaddition reaction between carbon dioxide and epoxides.Under mild reaction conditions,it shows good catalytic performance and obvious size selectivity.In chapter 3,the transition metal copper ions and the rigid triazole organic ligand4-（1H-1,2,4-triazol-1-yl）benzoic acid were selected to synthesize a two-dimensional double-layer MOFs materials containing pentacuclear copper cluster groups by a solvothermal method,and the molecular formula is[Cu₅（TABC）₄（COO）₂（H₂O）?11H₂O]（2）.[Cu₅O₂（COO）₆]is a secondary structural unit,which is assembled into a two-dimensional bilayer structure by connecting with four linear ligands.The window size of one-dimensional channel is 11.58?×11.52?,and supramolecular structure is formed byπ-πstacking.The complex has good chemical stability and thermal stability.After structural analysis,copper ions are in a coordination unsaturated state and can be used as Lewis acidic sites to catalyze the cycloaddition reaction between carbon dioxide and epoxides.Under mild reaction conditions,it shows good catalytic performance and obvious size selectivity.Due to the tight interlayer accumulation,the exposed catalytic active sites are limited,which reduces the recyclability of the complex in catalysis.In chapter 4,four rare earth metal ions of europium,yttrium,terbium,dysprosium and flexible organic ligand 4,4’-stilbenedicarboxylic acid containing ethylenic bond were selected to synthesize a series of hexanuclear rare-earth metal cluster-based MOFs materials with two-dimensional layer by solvothermal method.The molecular formula is{[（CH₃）₂NH₂]₂[Ln₆（μ-OH）₈（SDC）₃（CH₃COO）₆]·6H₂O}[Ln=Eu（3）,Y（4）,Tb（5）,Dy（6）].[Ln₆（μ₃-OH）₈（COO）₉]is a secondary structural unit,and each secondary structural unit is connected weith six adjacent SBUs through six linear ligands to form a two-dimensional layer structure.The complex has good chemical stability and thermal stability.After structural analysis,Ln³⁺ion is octacoordinated and in a coordination unsaturated state.It can be used as a Lewis acidic site to catalyze the cycloaddition reaction between carbon dioxide and epoxides.Under mild reaction conditions,the complexes show good catalytic performance and obvious size selectivity.Due to the good stability of the skeleton structure,the series of complexes also show good recyclability.Chapter 5 Conclusion:In this paper,the synthesis conditions,structure,physical and chemical properties of dinuclear copper cluster MOFs,pentanuclear copper cluster MOFs and hexanuclear rare earth cluster MOFs synthesized by solvothermal method were preliminarily explored,and their catalytic performance for the cycloaddition reaction of carbon dioxide and epoxides was summarized.