Design,Synthesis And Catalytic Properties Of Magnetic MNPs@MOFs Composite Catalysts

Metal nanoparticles@Metal-organic frameworks(MNPs@MOFs)composites have various structures and remarkable properties,which are widely used in the fields of catalysis,sensing,and separation,especially in catalysis.However,MNPs@MOFs composites usually have some limitations in catalysis,such as difficult separation in the recycling process,aggregation or leaching of the MNPs and applicable environments to be expanded,which restricts the development of MNPs@MOFs composite catalysts.The research content of this article is to summarize the current application limitations of MNPs@MOFs catalysts.Based on this,mgnetic MNPs@MOFs composite catalysts with new structures are designed and synthesized,to solve the above problems.In this article,two catalysts were successfully fabricated and applied to catalysis,including hollow magnetic Void nFe3O4@Pd/ZIF-8@ZIF-8 catalyst with double-shell structure and magnetic rodlike Fe3O4-NR@ZIF-8/Pt nanocatalyst with magnetically-actuated stirring function.And their catalytic performances were studied and summarized in detail.In the first part,a hollow magnetic spherical catalyst with double-MOF-shell denoted as Void nFe3O4@Pd/ZIF-8@ZIF-8,was fabricated to solve the limitations that majority of the MNPs@MOFs catalysts could only possess one of high catalytic activity and high recycling performance.Among the compositions of Void nFe3O4@Pd/ZIF-8@ZIF-8,the big cavity can effectively accelerate mass transfer,which could improve the catalytic activity;superparamagnetic Fe3O4 NPs of small particle size embedded in the inner ZIF-8 shell can enhance the separation and recyclability;the highly-dispersed Pd NPs are confined into the cavities of the inner ZIF-8 shell to avoid the agglomeration;the outer ZIF-8 shell contributes to maintaining the structural stability and has size-selective catalytic properties;As expected,the result of olefin hydrogenation at room temperature demonstrated the superiority of such a structure.In the second part,MNPs@MOFs catalysts have low mass transfer efficiency under external agitation,causing that their catalytic activity is easily restricted by diffusion meanwhile their structure is liable to broken due to the poor mechanical stabilities of MNPs@MOFs catalysts.In this work,a magnetic rodlike Fe3O4-NR@ZIF-8/Pt nanocatalyst with magnetically-actuated stirring function was synthesized to solve the above problems.Among the compositions of Fe3O4-NR@ZIF-8/Pt,the internal rodlike Fe3O4 NP have a certain length and can provide self-stirring function for the whole material;the highly-dispersed Pt NPs are confined into the cavities of the outer ZIF-8 shell to avoid the agglomeration;the whole Core-Shell structure is conducive to maintaining good stability of the catalyst.To prove the concept,Fe3O4-NR@ZIF-8/Pt catalyst showed excellent self-stirring catalytic performance and applications in different catalytic systems with better catalytic activity and stability than ZIF-8/Pt with external stirring catalysis.