Pd₂₄Cu₁₂ Cages with Open Tripalladium Nodes for Selective Hydrogenation

Metal-organic cages (MOCs) featuring palladium nodes have become a cornerstone in the field of supramolecular coordination chemistry. Despite the predominant emphasis on Pd(II), which has laid a fundamental basis for MOC assembly, substantial opportunities persist for the investigation of a wider array of structural building blocks. Consequently, the innovation of new palladium-based building blocks is of critical importance for realizing emergent functionalities and extending the application landscape of MOCs. In this study, we present the {Pd₃(SR')₃[PR₃]₃}⁺ (abbreviated as Pd₃) cluster as a unique building unit characterized by accessible metal sites conducive to catalytic activity of MOCs. The cluster undergoes a one-pot coassembly with Cu₂ units to yield a Pd₂₄Cu₁₂ cage, exhibiting a face-centered cubic architecture. Within this framework, eight Pd₃ nodes are situated at the corners, while six Cu₂ units are located at the face centers. The structure is maintained by 24 4-mercaptobenzoic acid ligands, where thiolate groups coordinate to the Pd₃ nodes and carboxylate groups bind to the Cu₂ units. Such a rigid framework, together with the electronic communication among the metal centers, accounts for the exceptional thermal and aerobic stability of the cage. Notably, the cage showcases high catalytic activity and selectivity in the hydrogenation of azobenzene. These findings not only introduce a class of catalytically active palladium nodes for the assembly of chemically different palladium-organic cages but also pave the way for further exploration of cage-based catalysts in hydrogenation processes.