The Coordination Restraint of Rh-Cu Di-Atomic Catalyst and Oxygen Insertion into C-H Bond for the Synthesis of Methanol

The direct oxidation of methane to methanol holds significant industrial value. In the methane-assisted oxidation and one-step methanol synthesis reaction, the oxidants or oxygen-containing groups are highly prone to deeply oxidize the dissociated methane molecules, making it difficult to control the reaction proces. This study, based on dual-atom catalysts, we regulate the reaction process by separating active sites at a short distance and constraining the activity of oxygen intermediates, enabling methanol formation through the oxygen insertion. Aiming at the precise construction of dual sites, we innovatively developed an encapsulated pyrolysis strategy and successfully synthesized Rh–Cu heteronuclear dual-atom catalysts (RhCu DACs) over nitrogen-doped graphite carbon supports, forming an Rh–Cu–N ₆ structural catalyst (Rh–Cu bond length = 2.42 Å). The electronic coupling between the bimetallic sites induces a significant charge polarization effect, enhancing the activation efficiency of reactant molecules. The introduction of the second metal, Cu, captures active oxygen species, generating a “restraint” effect on oxygen species. This restraint effectively inhibits excessive oxygen insertion, thereby inhibiting the complete oxidation of methane. The methanol selectivity is as high as 81% and the catalytic activity is three times than that of the single-atom Rh catalyst. In-situ Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations demonstrate that the rhodium-copper bimetallic centers form stable oxygen-bridged intermediate structure (Rh-O-O-Cu or Rh-O-Cu). The rhodium site acts as an electron acceptor for methyl groups (*CH ₃ ) to stabilize the formation of hydrocarbon intermediates, while the copper site restricts the activity of adjacent oxygen species and guides oxygen insertion into C-H bonds for methanol synthesis.