Preparation And Catalytic Performance Of Pd And Pd/Au Catalyst Supported On Aminopyridine Modified Graphene Oxide For Catalyzing Suzuki Coupling Reaction

In this paper,Pd catalyst(called as GO@CPn-Pd,n=1,2)and bimetallic Pd/Au catalyst(GO@CP2-Pd1Au1)supported on graphene oxide modified by aminopyridine were prepared by self-assembly method.The composition and structure of these catalysts were analyzed by a series of characterization methods.Their catalytic performance for Suzuki coupling reaction were studied.The main research contents and results are as follows:1.Graphene oxide was modified by monodentate 2-aminopyridine and bidentate 2,6-diaminopyridine ligands,then they were used to coordinate with Pd to form two heterogeneous catalysts(denoted as GO@CP1-Pd,GO@CP2-Pd).These catalysts were characterized by FT-IR,Raman,XPS,SEM,TEM,XRD,ICP-AES.The results showed that the molecular structure of ligands and the types of Pd sources used had a great influence on the distribution of catalytic centers.Bidentate 2,6-diaminopyridine could disperse and stabilize the Pd catalytic centers better,which affected the catalytic activity.The catalyst prepared with(PhCN)2PdCl2 as Pd source had better catalytic activity and recycling ability for Suzuki coupling reaction.2.The catalytic performance of GO@CP1-Pd and GO@CP2-Pd were investigated using Suzuki coupling as template reaction.The results showed that GO@CP2-Pd had higher catalytic activity than that of GO@CP1-Pd under the same reaction conditions.The Suzuki reaction could be highly catalyzed by GO@CP2-Pd(Pd 0.019 mol%),which had high TOF values of 58105 h-1 at 70? and 5158 h-1 at 30??respectively.The catalyst had good substrate applicability and could be recycled for 6 times.3.The catalytic mechanism in Suzuki reaction was studied by thermal filtration,kinetics,poisoning,in situ on-line IR and XPS.The results showed that the reaction catalyzed by GO@CP2-Pd was heterogeneous catalytic process occurred at the interface,and the active center was Pd0.The reasons for the deactivation of GO@CP2Pd during the catalytic cycle were investigated by XRD,Raman,XPS,TEM,ICP-AES.The results showed that the partial loss and aggregation of Pd active centers were the main reasons for the deactivation.4.A series of bimetallic Pd/M catalysts(called as GO@CP2-Pd/M)supported on graphene oxide modified by 2,6-diaminopyridine were prepared by self-assembly method.Their catalytic properties for Suzuki reaction were studied.GO@CP2-Pd/Au exhibited a higher catalytic activity than that of GO@CPn-Pd5 and among of them,the best catalytic performance could be achieved when Pd/Au ratio is 1:1 was used.The composition and structure were analyzed of catalyst GO@CP2-PdiAui were characterized by XRD,SEM-EDS,XPS and TEM.The results showed that Au mainly existed in the form of Au0 nanoparticles about 1.1 nm,while Pd mainly existed in the form of Pd2+.GO@CP2-Pd1Au1 could catalyze Suzuki reaction under mild conditions(30?,80 min,NaOH,H2O/C2H5OH)with TOF value of 12097 h-1,which is higher than that of GO@CP2-Pd(5158 h-1,30?).It also had a high catalytic ability for iodinated and brominated aromatic substrates.The catalytic mechanism in Suzuki reaction catalyzed by GO@CP2-Pd1Au1 was detailed studied by thermal filtration,kinetics,poisoning and XPS.The results showed that the reaction was heterogeneous catalytic process proceeded at the interface,and the active centers were Pd2+/Au0.