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Catalysis is closely related to our production and life, and the construction of high-efficiency catalysts is the goal of scientists in the field of catalysis
.
Metal nanocatalysts are the most common heterogeneous catalyst centers
At present, a lot of work has proved that small molecule modified metal catalyst is an effective means to improve catalytic performance
.
The traditional method is mainly to modify small molecules on the metal surface, but the modified small molecules will cover the metal active sites, which easily causes the contact between the substrate and the metal sites to be limited and is not conducive to the catalytic activity
Recently, the team of Professor Hailong Jiang from the University of Science and Technology of China coated highly active metal nanoparticles in a metal organic framework (MOF) to construct a metal@MOF composite catalyst.
Systematic regulation of the environment, thereby realizing the simultaneous optimization of the catalytic efficiency and selectivity of the metal sites
.
Figure 1.
The construction of Pd@MIL-101-Fx composite catalyst has significant advantages
Based on the modifiable amino sites in MIL-101-NH 2 and the post-synthetic modification method, the USTC team modified fluorine-containing small molecules into the MOF framework, and strategically constructed Pd@MIL-101-Fx (X= 3 , 5, 7, 11, 15) Nano composite catalyst
.
After hydrophobic modification, the MOF structure can be maintained, and the size of Pd can still be maintained and still be coated in the MOF pores
Figure 2.
Compared with Pd particles protected by surfactants and Pd particles coated with prototype MOF, the modified Pd@MIL-101-Fx (X= 3, 5, 7, 11, 15) is not only higher The catalytic activity can also be synchronized to optimize the reaction selectivity
.
In terms of catalytic application, the USTC team took the important industrial reaction of selective hydrogenation of nitrochlorobenzene as the research object, and evaluated the performance of the catalyst.
The results showed that the hydrophobically modified Pd@MIL-101-Fx can be selectively hydrogenated.
Catalyzes the hydrogenation of nitro functional groups without dechlorination, and efficiently obtains p-chloroaniline products with a conversion rate of >99% and a selectivity of up to 98%
.
In order to further study the reasons for high performance, the author combined the experimental characterization and DFT calculation results and found that in the modified Pd@MIL-101-Fx, the surface valence of Pd is normal, which will selectively adsorb higher electrons.
Figure 3.
This result was recently published in Chem.