Nonporous Self-Assembled Pd(II) Coordination Cage Enabling Dual Capture of Iodine and Methyl Iodide

The expansion of nuclear energy necessitates the development of advanced materials capable of managing volatile radioactive byproducts. Herein, we report the rational design and synthesis of a discrete metal-organic cage (MOC1), assembled through coordination interactions between Pd(II) acceptor (M) and tetratopic ligand (L), and its molecular boat-like structure was unambiguously determined by single-crystal X-ray diffraction. This pyridyl-functionalized architecture is specifically engineered for the simultaneous sequestration of molecular iodine (I₂) and methyl iodide (CH₃I). The nonporous coordination cage exhibits exceptional iodine capture performance, achieving a vapor-phase uptake of 2.54 g g^-1 at 75 °C and a solution-phase capacity of 338.8 mg g^-1 in n-hexane, driven by synergistic π-iodine and electron-pair interactions. Remarkably, it also displays dynamic vapor-phase adsorption with an uptake of 1.26 g g^-1. In addition, the cage effectively captures CH₃I vapor, reaching capacities of up to 1.10 g g^-1 through a nucleophilic methylation mechanism. Stability studies confirm that MOC1 retains its structural integrity and adsorption efficiency over at least five regeneration cycles. This work establishes an effective approach for designing recyclable metallo-assembly optimized for the remediation of iodine and organic iodides, significantly advancing the safety standards of nuclear power generation.