Multi-active sites in situ formed on Schiff-base Pd(II)/Cu(II) self-assembly monolayer supported on graphene oxide: A simple protocol to enhance the catalytic activity

Abstract

To understanding relationships between structure of multi-active sites and activity is help for rational designing high active catalyst. In this paper, organometallic Schiff-base Pd(II)/Cu(II) monolayers containing 2-[[(2-Aminophenyl)imino] methyl] phenol (Apimp) supported on graphene oxide (called GO@Apimp-Pd/Cu) were fabricated by self-assembly(SA), which showed a higher activity toward Suzuki coupling reaction with a turn over frequency (TOF) up to 3.07 × 105h − 1 mainly due to the compelling multi-active sites in situ formed on the surface during catalysis. Catalysis was heterogeneous and occurred on the surface of GO@Apimp-Pd/Cu demonstrated by hot filtration test, poison test, in suit IR and three-phase test. These multi-active sites included active Pd, PdO/CuO, Pd/PdO, Pd/CuO and Pd/Cu on the surface of catalytic monolayer, showing much higher activity than individual Pd site due to the electrons transferred from CuO to PdO and Pd, resulting in the period electron densities Pd δ+ (0<δ <2) acting as electron donor and receptor. This phenomenon could efficiently make not only oxidative addition and metal-translation, but reduction elimination proceeded readily. The enhanced activity was also attributed to the ensemble synergistic among all active sites. The results develop a promising heterogeneous catalytic monolayer with higher activity enhanced by ensemble synergistic of the multi-active centers.