Preparation Of Multicompartmentalized Porous Materials And The Catalytic Performance Study

Multicompartmentalized porous materials can provide high specific surface areas,tunable pore structures,multiple compartments,high accessibilities for reactants.These features make them having great advantages in the precise control of spatial localization of multiple catalytic active sites for the construction of efficient catalytic systems.It is an important research field to design and prepare multicompartmentalized porous materials with tunable structures and multiple functionalities for regulating catalytic reactions.Although some achievements have been realized,the potential of multicompartmentalized porous materials is still far from being fully exploited in rationally regulating complex catalytic reactions.This paper focuses on the preparation and catalytic applications of multicompartmentalized porous materials.In the second chapter of this paper,two different metal nanoparticles are co-localized in multicompartmentalized mesoporous organosilica materials（MCMOS）for regulating catalytic selectivity of hydrogenation reactions.Firstly,Ru nanoparticles（NPs）were encapsulated in the internal nanocavity of MCMOS by an impregnation reduction method.Then Au NPs were loaded into the surface grooves by a simple adsorption process.As a result,these two metal NPs were spatially isolated,producing a supported multimetal catalyst（Ru/Au/MCMOS）.It was found that the prepared Ru/Au/MCMOS catalyst showed a good catalytic performance with a conversion of 99.9%and a selectivity of 99.2%in the hydrogenation reaction of halonitrobenzene,while the Ru/MCMOS and Au/MCMOS catalyst was almost inactive.The catalytic activity of Ru/Au/MCMOS was 10.5 times higher than that of the traditional supported gold catalyst（Au/Ti O₂）and was also higher than those of most of the gold catalysts that were reported in the literatures.The activation energy of Ru/Au/MCMOS was proved to be lower than that of Au/Ti O₂.The role of Ru and Au NPs in the selective hydrogenation reaction was then studied.The experimental results showed that the Ru NPs were responsible for the activation and dissociation of hydrogen molecules and the hydrogenation of halonitrobenzene molecules dominantly occurred on the surface of Au NPs.Moreover,it was found that the hydrogenation reaction rate was first increased rapidly and then remained unchanged along with an increase of Ru-Au ratio.With the increase of the distance between Ru-Au,the reaction rate decreases significantly.On the basis of these results,we proposed a new catalytic mechanism of neighboring metal assisted hydrogenation.Specifically,hydrogen molecules are dissociated on the surface of Ru NPs,and the resulting active hydrogen atoms were migrated to the surface of Au NPs via the MCMOS support to react with the adsorbed halonitrobenzene molecules.Furthermore,we investigated the catalytic stability of Ru/Au/MCMOS and the universality of this neighboring metal assisted hydrogenation.The experimental results showed that the catalytic activity did not decrease significantly after successive five cycles.Ru/Au/MCMOS showed high catalytic selectivity in hydrogenation reactions of different halogenated nitroarenes.This new mechanism of neighboring metal assisted spillover hydrogenation has also been extended to different bimetallic catalytic systems and the selective hydrogenation reactions of phenylacetylene.In the third chapter,a new kind of multicompartmentalized covalent organic frameworks（MCCOFs）has been developed for metal-enzyme tandem catalysis.Firstly,MCCOFs were prepared via a process of amorphous-to-crystalline transformation followed by a Schiff base reaction between p-phenylenediamine and benzenetricarboxaldehyde.The obtained MCCOFs showed a uniform morphology of cross-wrinkled microspheres with an average particle size of 715 nm.Interestingly,MCCOFs contained both a hollow cavity in the particle interior and numbers of wrinkles on the particle surface,forming a multicompartmentalized structure.Moreover,the obtained MCCOFs had a good crystallization and thermal stability.By changing the dosage of acid catalyst,the particle size of MCCOFs materials was precisely adjusted in the range of 495-890 nm.Subsequently,the formation process of MCCOFs was investigated.The experimental results showed that covalent organic polymers with an amorphous framework and a uniform morphology of solid microsphere were first obtained from p-phenylenediamine and benzenetricarboxaldehyde at room temperature.Then,the covalent organic polymer microspheres were transformed into crystalline covalent organic frameworks under typical crystallization conditions,accompanied with the formation of hollow structures.Moreover,the smooth surfaces were converted into cross-wrinkled surface structures during the crystallization process.Finally,Pd NPs were encapsulated in the hollow interior of MCCOFs,and then lipase was adsorbed on the cross-wrinkled surfaces,producing a metal-enzyme tandem catalyst.The catalytic performance of this metal-enzyme tandem catalyst was explored in the ketone hydrogenation-kinetic resolution cascade reactions.