Atomically Precise AgCu Clusters Affixed to SiO₂ Aerogel for N-Formylation of Amines

Atomically precise metal clusters have gained academic interest for correlating their properties with their crystallographic structures at an atomic level. However, these clusters usually suffer from poor stability, precluding their industrial applications. Here, we overcome the limitation by constructing heterogeneous metal cluster catalysts, in which metal clusters are firmly affixed to the framework of SiO2 aerogel by means of the synergism between the surface metal of the cluster and oxygen of the aerogel, thereby significantly suppressing potential aggregation and fragmentation of the clusters during chemical reactions. This type of heterogeneous cluster catalyst exemplified by Ag17Cu12(SR)(12)(PPh3)(4)@aerogel in this work can catalyze the amine formylation with CO through a bifunctional mechanism: the Cu3S3 surface sites of the cluster are identified as the reaction sites for the amine activation and C-N bond formation; the basicity of the aerogel further improves the adsorption of the amine and CO onto the surface sites. This catalyst can reach similar to 90% formylation yield with 100% atomic utilization as well as remarkable stability. The facial strategy for the aerogel-fixed cluster catalysts can recognize high-performance cluster catalysts for heterogeneous reactions of academic and industrial importance.