Radiation Preparation And Catalytic Properties Of Noble Metal Modified MOFs

Metal-organic frameworks?MOFs?have many excellent properties,such as high porosity,large specific surface area and adjustable pore size.Due to these properties,MOFs can be used as catalysts or a carrier for catalysts,and have important application prospects.In this paper,a variety of noble metal nanoparticles modified metal-organic framework materials were prepared by irradiation technology.The micro-morphology and structure of the materials were characterized,and the catalytic performance was mainly tested and analyzed.The main research contents and results are as following:?1?Au/ZIF-8 composites were successfully prepared by gamma-ray radiation method using ZIF-8 MOFs with moderate particle size and regular crystal structure as a carrier.The results of SEM,TEM and XRD showed that the Au nanoparticles with a particle size of 7.2 nm are uniformly distributed on the framework of ZIF-8.The introduction of Ag nanoparticles did not destroy the framework structure of ZIF-8.The results of catalytic performance test show that Au/ZIF-8 composite has good catalytic ability for the hydrogenation of 4-nitrophenol?4-NP?to 4-aminophenol?4-AP?at room temperature.?2?A variety of Ag nanoparticles modified MIL-101?Cr?composites?1.6 wt%Ag/MIL-101?Cr?,2.0 wt%MIL-101?Cr?,2.1 wt%MIL-101?Cr??were prepared by double-solvent radiation method using octahedral MIL-101?Cr?MOFs as a carrier.The results show that Ag nanoparticles modified MIL-101?Cr?composites have regular octahedron structure,and its particle size was about 400nm.The Ag nanoparticles with diameters of 1.7±0.7 nm,2.0±0.7 nm and 2.1±0.5 nm were uniformly distributed in the framework.the introduction of Ag nanoparticles did not destroy the framework structure of MIL-101.The results of catalytic performance test showed that the catalytic time of 1.6wt%Ag/MIL-101,2.0 wt%Ag/MIL-101 and 2.1 wt%Ag/MIL-101 catalysts for reduction and hydrogenation of 4-NP at room temperature was about 8 minutes,6 minutes and 5 minutes.The first-order reaction kinetics constants were 0.396 min^-1,0.589 min^-11 and 0.609 min^-1,respectively.Therefore,the catalytic activity of 2.1 wt%Ag/MIL-101 catalyst was the highest.It was also found that 2.0 wt%Ag/MIL-101 catalyst could maintain 96.7%of its original catalytic activity after five cycles of recycling.?3?The magnetic core-shell structure MOFs loaded with silver nanoparticles?Fe₃O₄@MIL-100?Fe?/Ag?was prepared by gamma-ray radiation method.Fe₃O₄@MIL-100?Fe?/Ag have obvious core-shell structure,The core is Fe₃O₄ microspheres with a diameter of 400 nm and the shell is MIL-100?Fe?MOFs with a thickness of 50 nm.Ag nanoparticles with particle size of 2.0±0.8 nm are uniformly distributed in the MIL-100?Fe?channel.the introduction of Ag nanoparticles did not cause the collapse of the MIL-100?Fe?structure.VSM results show that the magnetic the composite has good magnetic properties and can be rapidly separated by magnets.The results of catalytic performance test show that the catalyst have excellent catalytic performance and can complete the reduction hydrogenation of 4-NP at room temperature for 60 s with a kinetic constant of 2.83 min^-1.After five cycles of recycling,the catalyst can still maintain 97.8%of its original catalytic activity.