Activation and Conversion of Methanol over M@SixCyBz Catalysts: Revealing the Impact of Boron Concentration and Metal Types on Activity and Selectivity Regulation.

Abstract

To address the challenges of poor stability and low product selectivity associated with metal catalysts in the CH₃OH to CHOOCH₃ reaction, innovative M@Si_xC_yB_z catalysts were constructed for the first time. In this work, encapsulated M@Si_xC_yB_z catalysts (Sc@Si₁₂C₁₂, Sc@Si₈C₁₂B₄, Sc@Si₄C₁₂B₈, Si₈C₁₂B₄, Cr@Si₈C₁₂B₄, and Mn@Si₈C₁₂B₄) are designed. First, molecular dynamics simulations demonstrate that M@Si_xC_yB_z catalysts exhibit high stability. Second, the mechanism of direct dehydrogenation of CH₃OH to CHOOCH₃ is systematically explored, the relevant data of each elementary reaction are calculated, and the reaction pathway is determined based on density functional theory (DFT). Finally, the electronic properties are calculated and analyzed. The results suggest that boron concentration can effectively regulate the product distribution and catalytic activity of CH₃OH conversion, and the metal types can affect the activity of CHOOCH₃ formation. Additionally, it is observed that the average charges of the carbon atoms at the reaction center of M@Si_xC_yB_z catalysts can be used as a descriptor for both activity and selectivity in CHOOCH₃ formation. Among them, Cr@Si₈C₁₂B₄ exhibits the highest activity for producing CHOOCH₃. The models and calculation results can facilitate high-value utilization of CH₃OH in the future.