Porous Organic Cage Liquid Stabilizes Pd Nanoclusters for Ambient H₂ Capture and Alkyne Semihydrogenation

The design and synthesis of novel supports for stabilizing highly active ultrafine metal nanoparticles (MNPs) is critically important across diverse scientific fields as it enables more efficient utilization of their high density of accessible active sites. However, the potential of emerging porous liquid (PL) materials to protect such MNPs remains largely unexplored. Herein, we report the rational design and synthesis of a new PL based on a porous organic cage (POC), termed CPOC-PL, constructed via condensation between four concave tetraformylcalix[4]resorcinarene caps and eight long-chain polyethylene glycol-functionalized diamino imidazole linkers. This [4+8] CPOC-PL features a square-prismatic cavity that serves as an excellent host for encapsulating and stabilizing ultrasmall Pd nanoparticles (∼1.36 nm in diameter) through a coordination-reduction process. The resulting Pd@CPOC-PL exhibits notable hydrogen gas uptake under ambient conditions, with ∼2.1 H atoms per Pd atom. Leveraging its fluidic nature and efficient hydrogen capture ability, Pd@CPOC-PL also demonstrates outstanding catalytic performance in the semihydrogenation of alkynes at ambient conditions. This work presents a generalizable strategy for the rational construction of functional POC-based porous liquids for practical applications.