Atom by Atom Condensation of Sn Single Clusters within Gold-Phosphorus Metal-Inorganic Porous Networks

Surface supported single-atom catalysts (SACs) and single-cluster catalysts (SCCs) have been an area of rapidly growing interest due to their high efficiency of metal atom utilization and high selectivity and activity toward various catalytic reactions. However, achieving highly dispersed, structurally well-defined SACs and SCCs with high surface loadings while avoiding their sintering to larger nanoparticles (NPs) still remains a nontrivial challenge. Here, by utilizing a recently fabricated porous metal-inorganic gold-phosphorus (AuP) network, highly dispersed single Sn clusters with high surface density can be realized. This is attributed to a synergistic effect of the P₆Au₆ pores for providing the preferential binding sites to anchor Sn atoms and the role of P₉ units as a blocking barrier to prevent the growth of Sn to larger NPs. The atom by atom condensation process of Sn single clusters with sizes ranging from monomers to heptamers as well as their binding configurations with the supporting surface are precisely identified at the atomic level, through the combination of a low-temperature scanning tunneling microscope and density functional theory calculations. Our approach opens new opportunities of utilizing metal-inorganic porous networks for the stabilization of highly dispersed and well-defined SACs and SCCs.