“…Compared with homogeneous catalysts, the heterogeneous catalysts, which are convenient for recycling from the reaction environment and readily used in flow reactors, are more popular, in particular in large-scale production 16 . During the past decade, great progress has also been made in heterogeneous Pd catalysts for oxidation processes, for example, Pd/hydroxyapatite 17 , Pd/mesoporous silicas 18,19 polymer-supported Pd 20,21 , carbon nanotubesupported Pd 22,23 , Pd supported on metal oxide 24 , Pdcontaining metal-organic frameworks 25 etc.…”