Template-free Synthesis of Graphene-like Carbons as Efficient Carbocatalysts for Selective Oxidation of Alkanes
Selective oxidation of aromatic alkanes by C-H activation is one of the key reactions in organic synthesis and chemical industry. It is of particular interest to activate C-H bond to get high-value added products under mild conditions by using sustainable carbocatalysts. Herein, we report a sustainable, green and template-free strategy towards the fabrication of N-doped and N/S codoped carbon nanosheets by metal-free carbonization of bioprecursor guanine and guanine sulfate. The occurrence of thin and N/S codoped carbon nanosheets was induced by multiple interactions of nucleobase. Benefiting from the unique textural structure of the as-synthesized carbons, including ultrathin thickness, optimal porosity, rich structural defects and synergistic coupling effect of multiple dopants, the carbon nanosheet delivers a high catalytic performance with 85% ethylbenzene conversion and 98% selectivity of acetophenone at 80 oC after 4 h reaction, which outperforms other equivalent benchmarks (e.g. 8.5 times in conversion and 3.2 times in selectivity higher than OCNT). Density functional theory simulations indicate that the oxidation of ethylbenzene is catalyzed by synergic effect of p-N/S and g-N/S catalysts via OH radical mechanism. This N/S codoped strategy provides guidance for the design of carbon-based catalysts for selective oxidation of other alkanes.