Dual Single-Atom Catalysts Unveiling Active Sites for Enhanced Ethylene Methoxycarbonylation

Designing heterogeneous catalysts with well-defined structure remains crucial for identifying true active sites and achieving superior performance. Here, we report a series of Ru-based dual single-atom catalysts (DSACs) constructed on TiO₂, in which catalytically inert second metals (Zn, Mn, Mo, In) delicately modulates the electronic structure of Ru. Among them, Ru₁Zn₁/TiO₂ with most electron-deficient Ru site exhibits highest activity and durability for acid-free ethylene methoxycarbonylation (EMC) with a turnover frequency of 1403 h^-1-one to two orders of magnitude higher than previously reported Ru-based catalysts, ranking among the most efficient heterogeneous EMC catalysts. Benefiting from well-defined and fine-tuned structure of DSACs, an unambiguous establishment of the structure-activity relationship has been achieved, pinpointing electron-deficient Ru^δ+ species as the true active sites for the EMC reaction. Further DFT calculations reveal the electronic coupling in Ru-Zn site optimizes the d-band center near the Fermi level, and facilitates the adsorption and activation of reactants, thereby reducing the energy barrier for the C-C coupling step. This work establishes a general strategy for constructing bimetallic single-atom catalysts as precise model systems for elucidating active sites and guiding the rational design of efficient and stable catalysts for carbonylation and related transformations.