Schiff-based Pd(II)/Fe(III) bimetallic self-assembly monolayer---preparation, structure, catalytic dynamic and synergistic

Abstract

Graphene oxide supported Pd (II)/Fe (III) bimetallic catalytic monolayer (denoted as GO@H-Pd/Fe) was prepared and characterized. Its catalytic performances for Suzuki coupling reaction, synergetic effect and catalytic mechanism were systematic investigated. Results showed that orientation, composition and distribution of catalyst had efficient effect on catalytic activity. Catalytic activity of GO@H-Pd0.10/Fe0.90 was 475 times more than that of GO@H-Pd due to the ordered catalytic monolayer immobilized on GO, proper ratio of Pd/Fe and the synergetic effect between Pd(II) and Fe(III) which could form active cluster containing Pd and Fe. The Pd(II) could be made more negative by transferring electron from GO to Fe(III) via ligand and then to Pd, improving its catalytic activity since it was easy for oxide addition. It also exhibited better stability and recyclability at least 8 times due to proper functional ligand and support. Deactivation mechanism was confirmed to be the aggregation of active centre during the recycling. Heterogeneous catalytic mechanism was also proved by poison test, hot filtration and ReactIR. The results of ReactIR presented different dynamic catalytic process for GO@H-Pd0.10Fe0.90 and homogeneous catalyst (Li2PdCl4/FeCl3·6H2O).The activation energies were 9.7 KJ/mol and 3.7 KJ/mol obtained for heterogeneous and homogeneous catalyst, respectively. Considering the diffusion effect, the factor of supports on the activity was also investigated by ReactIR, with which that GO@H-Pd0.10Fe0.90 catalytic activity was higher than that of homogeneous catalyst could be confirmed.