Pre‐Amination‐Directed In Situ Growth of Supported High‐Index Faceted Noble Metal Nanocrystals

Noble metal nanocrystals with high‐index facets exhibit superior catalytic activity but are challenging to synthesize on solid supports due to thermodynamic preference for low‐energy facets and uncontrolled metal‐support interactions. Here, we propose a pre‐amination‐directed strategy wherein grafting amino‐silanes onto supports fundamentally redirects the in situ growth of high‐index faceted nanocrystals. The pre‐installed amino groups coordinate with metal precursors to form stable surface complexes which, upon thermal activation, generate localized reducing environments that orchestrate facet‐selective nucleation and growth. Through synergistic regulation via coordination chemistry, electrostatic stabilization, and steric effects, this approach yields ultrasmall polyhedral nanostructures (4∼7 nm) enriched with abundant high‐index facets, effectively addressing the fundamental limitations of conventional synthetic routes, which tend to yield oversized particles (>50 nm) and are prone to ligand‐induced surface contamination. The strategy proves universally applicable across Pt, Pd, and Au‐based systems, delivering nanocrystals with remarkably low coordination numbers (4.0∼7.2) and superior catalytic performance (e.g., T 90 = ∼150°C for toluene oxidation by Pt‐based catalysts). Our work establishes pathway engineering through pre‐amination as a general principle for designing supported high‐index faceted noble metal nanocrystals for diverse catalytic applications.