Methane C-H Activation by Cyclo[18] Carbon-based Single-atom Transition Metal(Os, Ir)

It is of great significance and challenge for the conversion and utilization of methane(the main component of natural gases) due to its high stability in chemistry. In order to breakthrough out it, the key is to develop the catalysts for methane C-H activation under mild conditions. Here, we investigated methane C-H activation over cyclo[18] carbon-based single-atom transition metal(TM=Os, Ir)(TMC18) by means of density functional theory (DFT). The results show that the activation barrier of methane C-H over TMC18 is significantly lower than TM itself, and the species CH3 resulted from methane C-H cleavage tends to bind more weakly with TMC18 than TM+ ions. The weakened interaction between CH3 and TMC18 favors to the CH3 desorption or further transformation into value-added chemicals. Thus, cyclo[18] carbon-based single-atom TM exhibits its promising ability to high-efficiently activate C-H of methane at mild conditions. The detailed analysis on the interaction of TM with cyclo[18] carbon indicate that cyclo[18] carbon is good in electron-storage/attraction by d-pi conjugation of TM-cyclo[18] carbon, which leads to the decrease in barrier of methane C-H activation over cyclo[18] carbon -based TM.