Syntheses And Tandem Catalytic Performances Of MOF-based Catalyst With Biactive Sites

Metal organic frameworks?MOFs?materials are self-assembled from metal ions or metal clusters and organic ligands,which have high high porosity,acceptable stability,adjustable pore volume and flexible structure.The open unsaturated coordination sites of MOFs node metal ions/clusters can play Lewis acid catalytic role MOFs.The organic ligands of MOFs can also play a catalytic role by introducing functional groups.Meanwhile,due to the stable pore structure,MOFs can be used as platform to load the guest active center?such as metal nanoparticles,small organic molecules and enzyme?.Therefore,MOFs are widely used in the field of heterogeneous catalysis.At present,one of the trends in MOF-based catalysts is to simulate nature by developing multicatalysis systems,wherein multiactive sites are integrated into a single network for sequential tandem catalysis.Tandem reactions are a powerful synthesis strategy in organic chemistry,which usually involve two or more sequential reactions,without separating intermediates until generating the final product.From the point of green chemistry,tandem reactions can effectively reduce the use of solvents,improve the economy of conversion steps,consequently improve the reaction efficiency and reduce resource consumption.Although there have been many reports on MOF-based catalysts,the application of MOF-based catalysts with bifunctional active sites in tandem reactions is still rare.This paper designed a synthesis strategy of multifunctional heterogeneous catalytic materials,which successfully encapsulates Pd nanoparticles and Zn²⁺open sites into the MOF framework,and its catalytic performance in one-pot alcohol oxidation-aldehyde cyanosilication tandem reaction was studied.First,we choose 2'-Amino-1,1':4',1''-terphenyl-4,4''-dicarboxylic acid and 2',3',5',6'-tetramethyl[1,1':4',1''-terphenyl]-4,4''-dicarboxylic acid as ligands to form Ui O-68-NH₂-CH₃,then through post synthesis metallization and H₂ reduction to load Pd nanoparticles and open characterized by XRD,SEM,TEM,XPS and N₂ adsorption etc.The results showed that the composite was octahedral structure with average sizes of 800 nm-1000 nm.Pd nanoparticles were highly dispersed in the MOF framework with an average particle size of 2.1±0.2 nm.The prepared Pd⁰-Zn^II@Ui O-68 composite material was utilized as catalyst in one-pot alcohol oxidation-aldehyde cyanosilicatization tandem reaction.The results indicated that the catalyst showed excellent catalytic activities under mild conditions.Meanwhile,the yield was up to 95%with various substituents.In addition,the circulation experiment and the filtration experiment proved that the MOF has good recyclability,which structure and catalytic activity can be maintained after 3 cycles.