A Nitrogen-Enriched Pd₃L₆ Cage Assembled from Hydrogen-Bonded Triazole Foldamers for Chemisorption-Driven Methyl...

The effective capture of radioactive CH₃I under high-temperature and low-concentration conditions remains a critical challenge in nuclear waste management. Herein, we report a supramolecular strategy that combines intramolecular hydrogen bond-directed ligand preorganization with metal-coordination assembly to construct a nitrogen-enriched metal-organic cage for CH₃I capture. Accordingly, a hydrogen-bonded triazole ligand selectively assembles with Pd(II) to form a discrete Pd₃L₆ cage featuring a large, accessible cavity arrayed with inwardly oriented triazole nitrogen atoms, thereby creating a confined nucleophile-rich microenvironment for CH₃I adsorption. The cage captures CH₃I through a chemisorption-driven pathway involving nucleophilic alkylation of the triazole nitrogen atoms to generate N-methylated triazolium sites, which further promote additional noncovalent uptake within the cavity. The assembled cage exhibits an excellent CH₃I adsorption capacity (1.69 g g^-1, 48.7 mol mol^-1) and rapid uptake kinetics (0.17 g g^-1 h^-1) under static conditions. More importantly, it represents the first cage adsorbent shown to capture CH₃I under simulated nuclear off-gas conditions, achieving a dynamic adsorption capacity of 0.13 g g^-1 at 150 °C and a CH₃I flow rate of 0.8 mg min^-1. This work establishes hydrogen bond-directed foldamer preorganization as a supramolecular strategy for constructing metal-organic cages with confined reactive cavities for challenging molecule capture.