【摘要】 由于高度的化学稳定性,作为天然气主要成分的甲烷分子的转化和利用极富挑战性和研究意义.然而，这一问题的突破有赖于甲烷C—H的活化,特别是温和条件下活化催化剂的研发.本文采用密度泛函理论方法计算考察了过渡金属TM（Os, Ir）单原子-碳18环(TMC₁₈)对甲烷C—H的活化.结果表明,相对于TM单原子,TM单原子键合在碳18环上后,显著降低了甲烷C—H的活化能垒;而相较于TM单价阳离子,则削弱了C—H键裂解物种CH₃与TM的结合力.结合力较弱的TM-CH₃,对物种CH₃的脱附或进一步转化为附加值高的化学品有利.对TM-碳18环间的作用进行分析发现，碳18环通过与TM的d-π共轭,呈现良好的储存和吸电子的作用,进而可以促进甲烷C—H活化能垒的降低.碳18环基TM单原子具有温和条件下高效活化甲烷C—H的潜力.更多还原

【Abstract】 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-π conjugation of TM-cyclo[18] carbon, which leads to the decrease in barrier of methane C—H activation over cyclo[18] carbon-based TM.更多还原