Surface defects in atom-precise copper nanoclusters and their different catalytic efficiencies

Abstract

Significant strides have been made in crafting uniform nanostructures leveraging inherent nanomaterial defects. However, a basic understanding of the influence of these intricate defects on their catalytic activities at the atomic level remains challenging. Herein, we report two similar surface-vacancy defects in two distinct nanoclusters, [Cu₂₀S(PET)₁₈(P(Ph-^pMe)₃)₃]⁰ (Cu₂₀S) and [Cu₁₃H₁₀(PPh₃)₇(SPhCl₂)₃]⁰ (Cu₁₃H₁₀), and their strikingly different catalytic efficiencies (PET = 2-phenylethanethiolate). Both clusters possess a face-centered cubic packing (fcc) metal core with a defect exposing Cu(111) plane: Cu₂₀S has a tetrahedral skeleton, while Cu₁₃H₁₀ adopts a cubic configuration. Both defects can be conceptualized as the loss of a –Cu[P(PhR₃)₃] (R = ^pMe or H) vertex. Intriguingly, only Cu₁₃H₁₀ exhibits remarkable efficiency in phenylacetylene semi-hydrogenation. NMR and theoretical studies identified the defect in Cu₁₃H₁₀ as the catalytically active site. Specifically, DFT calculations revealed a subtle atomic distinction that governs the catalytic activity, namely, in Cu₁₃H₁₀, migration of the central interstitial hydride to the surface defect site activates the catalytic reactions; in Cu₂₀S, copper migration creates an inefficient defect. It is hoped that this work will promote further research in the area of atomic-level chemistry of surface defects in nanoclusters, thereby paving the way for the rational design of functional nanomaterials in fields such as catalysis.