Separation of MnWO_x and NaWSiO_x Phases Boosts Oxidative Coupling of Methane

The oxidative coupling of methane (OCM) is an attractive approach for methane transformations, but achieving a satisfactory combination of activity and selectivity remains challenging, even with the promising Mn-Na₂WO₄/SiO₂ catalyst. Herein, we demonstrate that nanoscale separation of Mn-based and Na₂WO₄-based phases results in a highly efficient catalyst, achieving a remarkable 79% selectivity for C₂-C₃ hydrocarbons at a 32% CH₄ conversion at 775 °C, outperforming most previously reported catalysts. Our studies reveal that MnWO_x phases with adjustable surface Mn/W ratios and redox activities are more effective for the selective activation of O₂, thereby enhancing the OCM of CH₄. The assembly of MnWO_x and Na₂WO₄/SiO₂ components in nanoscale proximity significantly promotes the formation of C₂-C₃ hydrocarbons by suppressing deep oxidation. We propose a bifunctional mechanism involving the transfer of active oxygen species from MnWO_x to Na₂WO₄/SiO₂, which induces selective activation and coupling of CH₄ on the Na₂WO₄/SiO₂ surface.