Study On The Synthesis Of Multinuclear Rare Earth Complexes And The Application Of CO₂ Fixation

With the acceleration of industrialization,CO₂ emissions have gradually increased,and the greenhouse effect has enlarged,causing many environmental problems.The fixation and conversion of CO₂ has important theoretical and practical significance.Rare earth complexes are characterized by high coordination number,variable coordination modes,high Lewis acidity,and strong oxygen affinity.Many important results have been achieved in structural design and function exploration,including luminescence,recognition,catalysis,and energy conversion.The potential application value is favored by scientific researchers.The application of rare earth complexes for the fixation and conversion of CO₂ has important research significance.This dissertation focuses on the structure design and application research of multi-nuclear rare earth functional complexes.We designed and synthesized a series of Schiff base ligands and acylhydrazone ligands,obtained multinuclear rare earth complexes with different structural characteristics through coordination self-assembly,and further studied their applications in CO₂ fixation and conversions.This provides reference and guidance for future ligand design,the preparation of novel structural complexes,and the application of complex catalysis.The full text is divided into five parts:1.Briefly introduce the application research progress of CO₂ resource utilization,rare earth complexes in CO₂ fixation and catalytic conversion of CO₂ into cyclic carbonate.2.A flexible Schiff base ligand H₃L¹ was designed and synthesized.A series of binuclear triple-helical complexes that fix CO₂ in the air in the form of carbamate was obtained by using this ligand,and the self-assembly process and magnetic properties were further studied.3.A series of Schiff base ligands H₅L²-H₅L⁴ with the same terminal group and different chain lengths were designed and synthesized.Through the self-assembly process,CO₂ in the air can be fixed in the rare earth complexes,and the fixing method of CO₂ with the increase of chain length from the carbonate form to the carbamate form,the structure of the complex is transformed from a mononuclear to a multinuclear structure at the same time.4.A flexible acylhydrazone ligand H₄L⁵ was designed and synthesized.By adjusting the alkalinity to influence the self-assembly process,two multinuclear rare earth complexes with different structures were constructed and applied to catalyze the cycloaddition of CO₂ and epoxy compounds.In the reaction,the influence of the structure on its catalytic performance was studied,and the possible catalytic mechanism was proposed.5.Using flexible acylhydrazone ligand H₄L⁵,a series of dodecanuclear cyclic 3d-4f heterometallic complexes based on Zn²⁺and Ln³⁺have been constructed.They were successfully applied to catalyze the reaction of cycloaddition of CO₂ and epoxy to obtain cyclic carbonate.The catalytic performance of the complexes was further investigated in detail,and the possible catalytic mechanism was discussed.