Atom-by-atom size-evolution of Ag13-Ag15 nanoclusters: structure and catalytic CO2 conversion

The atomic precision of metal nanoclusters reveals their size-dependent physicochemical properties and highlights the challenges in achieving controllable synthesis at the single-atom level. Herein, we report a series of silver clusters adopting an atom-by-atom evolution pattern, including Ag 13 (SR 1 ) 12 (DPPP) 3 , Ag 14 (SR 1 ) 12 (DPPF) 3 , and Ag 15 (SR 1 ) 12 (DPPB) 3 (Ag 13 -Ag 15 , HSR 1 and DPPP/DPPF/DPPB denote 3,5-bis(trifluoromethyl)thiophenol, and 1,3-bis(diphenylphosphino)propane/ferrocene/butane). Each of these three clusters comprises a shell structure with three groups of Ag 2 (SR 1 ) 4 (DPPX) (X=P/F/B) blocks, while the metallic core corresponds to singly, linearly, and triangularly capped distorted octahedral Ag 6 structures. So far, Ag 13 represents the first 1e metal cluster. The kinetic monitoring and the molecular dynamic (MD) simulations demonstrate the nucleation driven by ligand flexibility. The structural peculiarities of the nanoclusters (which are loaded on activated carbon) govern their divergent catalytic behaviors in epoxide carboxylation reactions. The DPPF stabilized Ag 14 cluster exhibits high activity (98 % yield in 20 h at 75°C, and well maintained after 5 cycles), outperforming Ag 13 (56 %) and Ag 15 (65 %) under otherwise identical conditions. The DFT results show that CO 2 could be significantly stabilized by parallel benzene rings around AgS 2 in Ag 14 , forming π-CO 2 -π structures. This study establishes a dual structure–activity relationship: ligand flexibility regulates the nucleation process during synthesis, whereas the resultant surface defects induced by rigid ligands determine catalytic performance.