Preparation Of Pd Supported Hollow/Yolk-Shell/Core-Shell Composite Materials And Its Catalytic Reduction Of Nitrophenol

Nanomaterials exhibit unique properties such as quantum effects,enhanced Raman scattering,magnetism,optics,etc.,and are widely used in fields such as electronics,biomedical,energy,environment,and chemistry.Combining different nanomaterials into composite materials can achieve more functions and applications,among which the hollow/yolk-shell/core-shell structured materials are a class of special nanomaterials with high research value.They have rich physical and chemical properties and have received extensive attention and application in biomedical,sensing,energy,and chemical engineering fields.Although special structured nanomaterials have broad potential in various application fields,there are still many bottlenecks and challenges in their development and preparation due to the complexity of their structures.Therefore,it is of utmost importance to study and develop simple,controllable,and universal synthesis methods for hollow/yolk-shell/core-shell structured nanomaterials.This paper focuses on the synthesis and control of the structure and morphology of inorganic porous composite materials,using hollow mesoporous silica nanoparticles（HMSN）,metal-organic frameworks（MOFs）,and metal oxides（MO）as the research objects.At the same time,the synthesized special structured nanomaterials are used as catalyst carriers for loading palladium metal nanoparticles and studying the catalytic reduction of 4-nitrophenol（4-NP）in water.The obtained research results are as follows:1.A"stepwise vacuum evaporation"method has been developed to achieve confined growth of nanoscale metal-organic framework（MOF）crystals by gradually loading MOF precursors into the cavities through vacuum negative pressure and the capillary effect of hollow mesoporous silica nanoparticles（HMSN）induced by the initiator.By adjusting the types of MOF precursors,this method has been extended to various types of MOF nanocrystals,including ZIF-8,ZIF-90,HKUST-1,MIL-53（Cr）,and Ui O-66-NH₂.Ui O-66-NH₂@HMSN was obtained and further functionalized by depositing palladium metal nanoparticles.Due to the unique nanoscale confined environment and structural features of the carrier,this functionalization increased the exposure of active catalytic sites of Pd loading,which in turn resulted in enhanced catalytic activity and stability of the material in the 4-NP catalytic reduction experiment.2.A simple hard-template synthesis strategy was employed to prepare hollow/yolk-shell/core-shell Fe₃O₄@Zr O₂ nanostructures by utilizing the hydrolysis reaction of zirconium source on the hard template to form Zr O₂ shell and selectively etching the Si O₂ template to control the synthesis.The prepared Fe₃O₄@Zr O₂composites with different structures were further functionalized by loading Pd metal nanoparticles,and the effects of different structures and morphologies on catalytic activity were compared.The study discovered that the Fe₃O₄@m-Zr O₂ nanocomposite with yolk-shell structure possesses a unique structural configuration,where the physical interactions generated by the core prevent the aggregation of Pd metal nanoparticles,while the pore structure restricts their leaching.Consequently,the catalyst exhibits excellent catalytic activity towards the reduction of 4-nitrophenol under ambient conditions and can be easily recovered using a magnetic field due to its magnetic property.