Atomic-level engineering of single Ag¹⁺ site distribution on titanium-oxo cluster surfaces to boost CO₂...

Precise control over the distribution of active metal sites on catalyst surfaces is essential for maximizing catalytic efficiency. Addressing the limitations of traditional cluster catalysts with core-embedded catalytic sites, this work presents a strategy to position catalytic sites on the surfaces of oxide clusters. We utilize a calixarene-stabilized titanium-oxo cluster (Ti₁₂L₆) as a scaffold to anchor Ag¹⁺ in situ, forming the unique nanocluster Ti₁₂Ag_4.5 with six surface-exposed Ag¹⁺ sites. The in situ transformation from Ti₁₂L₆ into Ti₁₂Ag_4.5 clusters was traced through mass spectrometry, revealing a solvent-mediated dynamic process of disintegration and reassembly of the Ti₁₂L₆ macrocycle. The unique Ti₁₂Ag_4.5 cluster, featuring a surface-exposed catalytic site configuration, efficiently catalyzes the electroreduction of CO₂ to CO over a broad potential window, achieving CO faradaic efficiencies exceeding 82.0% between -0.4 V and -1.8 V. Its catalytic performance surpasses that of bimetallic Ti₂Ag₂, which features a more conventional design with Ag¹⁺ sites embedded within the cluster. Theoretical calculations indicate that the synergy between the titanium-oxo support and the single Ag¹⁺ sites lowers the activation energy, facilitating the formation of the *COOH intermediate. This work reveals that engineered interactions between active surface metal and the oxide support could amplify catalytic activity, potentially defining a new paradigm in catalyst design.