Metal Active‐Site Exposure via Ligand Engineering Boosts CO ₂ ‐to‐Ethylene Conversion on Cu ₁₈ 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 [Cu 18 H 17 (EtPP) 10 ] + ( Cu 18 ‐1 ) and [Cu 18 H 17 (TPP) 10 ] + ( Cu 18 ‑2 ), via ligand engineering. Although they share a similar metal‐core structure, their surface/ interface interactions exhibit marked differences. In the CO 2 electroreduction reaction, Cu 18 ‐1 exhibits 70.59% selectivity for C 2 H 4 with an industrial‐grade current density of −2.99 A·m −2 , both of which are approximately twice those of Cu 18 ‐2 . This enhancement originates from the weaker intramolecular interactions in Cu 18 ‑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.