Metal Active-Site Exposure via Ligand Engineering Boosts CO₂-to-Ethylene Conversion on Cu₁₈ Nanoclusters

In nano-catalysts, constructing isostructural counterparts with precisely tunable surface and interface properties to unveil their structure-activity relationships remains a significant challenge. Herein, we report the synthesis of two atomically precise, isostructural Cu hydride nanoclusters [Cu₁₈H₁₇(EtPP)₁₀]⁺ (Cu₁₈-1) and [Cu₁₈H₁₇(TPP)₁₀]⁺ (Cu₁₈‑2), via ligand engineering. Although they share a similar metal-core structure, their surface/ interface interactions exhibit marked differences. In the CO₂ electroreduction reaction, Cu₁₈-1 exhibits 70.59% selectivity for C₂H₄ with an industrial-grade current density of -2.99 A·m^-2, both of which are approximately twice those of Cu₁₈-2. This enhancement originates from the weaker intramolecular interactions in Cu₁₈‑1, which facilitate phosphine‑ligand stripping under reaction conditions, thereby exposing more metal active sites and promoting C─C coupling. The mechanism is corroborated by post‑reaction mass spectrometry, theoretical calculations, and electrochemically active surface area measurements. This work provides fresh insights into the rational design of metal-organic catalysts through ligand‑engineered regulation of intramolecular interactions.