Research On The Design, Synthesis And Catalytic Application Of Rhodium-supported Organometallic Porous Catalytic Materials

The rhodium organometallic catalyst has excellent activity and selectivity,but it is difficult to separate and recover from the reaction system,which causes environmental pollution and hinders large-scale industrial applications.In recent years,the research on immobilized organometallic catalysts has received more and more attention.This is because the immobilization of organometallic catalysts can overcome the shortcomings of homogeneous catalysts that are difficult to separate from the reaction system and cannot be reused.Pollution problems caused by heavy metals and other toxic and harmful substances have achieved the purpose of reuse,energy conservation and environmental protection.This thesis focuses on the design and synthesis of rhodium-supported organometallic porous catalytic materials and their catalytic applications.The main research contents are as follows:1.In order to solve the loss of precious metals and avoid polluting the environment,we prepared Rh₂?esp?₂@ZIF-8 catalyst on ZIF-8 by encapsulating Rh₂?esp?₂ in a one-pot method.The first implementation of Rh₂?esp?₂was achieved,successfully loaded.2-methylimidazole played a crucial role in the construction of this heterogeneous catalyst.It can not only modify the axial modification of Rh₂?esp?₂,but also participate in the formation of ZIF-8 supported catalysts.In this process,the reaction conditions in the catalyst synthesis process were optimized to select the best catalyst and apply it to catalyze the synthesis of N-H heterocyclopropane compounds.In this section,the structural formula of 2-methylimidazole and Rh₂?esp?₂ after coordination is also analyzed by single crystal test.Through axial coordination,2-methylimidazole can change the electron arrangement around rhodium.When applied to the synthesis of NH heterocyclic propane compounds,the selectivity of the product can be improved,and the reason for the increase in selectivity when catalyzed by Rh₂?esp?₂-2-MI is proved by DFT calculations,and the Rh₂?esp?₂ mechanism of2-MI and Rh₂?esp?₂@ZIF-8 in catalyzing the synthesis of N-H heterocyclopropane from olefins.Through catalyst application experiments,Rh₂?esp?₂@ZIF-8 can be cycled five times during catalysis and still maintain high activity and selectivity.2.Based on the concept of the Rh₂?esp?₂@ZIF-8 heterogeneous catalyst synthesized in the first part,other organometallic rhodium heterogeneous catalysts are constructed.In this part,Rh₂?OOCCF₃?₄,Rh₂?OOCCH₃?₄,[RhCl?C₂H₄?₂]₂ was tried to realize the possibility of[RhCl?C₂H₄?₂]₂being immobilized with ZIF-8 as a carrier.Heterogeneous catalysts were analyzed by TEM,XRD,XPS,etc.,and showed high crystallinity and good morphology.Due to the strong acidity of[RhCl?C₂H₄?₂]₂,the acidity in the solution is conducive to the growth of the ZIF-8 framework,so the size of the heterogeneous catalyst is larger than Rh₂?esp?₂@ZIF-8.The catalyst has good activity and repeated application stability in catalyzing the reaction of arylboronic acid and unsaturated carbonyl compounds.