LAUSR

The controlled synthesis of subnanometer‐sized metal clusters (MCs) presents a fascinating prospect for the research of size‐dependent properties. In this study, a facile approach by employing porous racemic organic cage crystals as supports for immobilizing a broad range of noble MCs (e.g., Ru, Ir, Rh) is reported. Downsizing the support to the nanoscale leads to resultant MCs with precisely controlled sizes < 0.7 nm. Such enhanced stabilization ability is a result of enhanced metal–support interactions as well as the nanoconfinement of organic cages in controlling the growth of MCs. Moreover, the obtained MCs display excellent catalytic performance in a series of liquid‐phase reactions owing to a decrease in the diffusion resistance from the substrate to MCs immobilized by the nano‐sized cage support.