The effective capture and storage of radioiodine are of worldwide interest for sustainable nuclear energy. However, the direct observation of ambiguous binding sites that accommodate iodine is extremely rare. We presented herein a crystallographic visualization of the binding of iodine within mesoporous cages assembled from aluminum molecular rings. These nanocages are formed through π-π interactions between adjacent aluminum molecular rings. Compared with the general nanotubes arrangement, the supramolecular nanocage isomer exhibits better iodine adsorption behavior. The robust molecular nanocages demonstrate a high iodine vapor saturation uptake capacity of 50.3 wt % at 80 °C. Furthermore, the resulting adsorbent can be recycled. Single-crystal X-ray diffraction reveals binding sites of molecular I2 within the pores of the phenyl-based linkers stabilized by the strong I···π interactions. These compounds represent an excellent model to deduce the trapping mechanism of guest molecules interacting with the host. In addition, this work develops a promising cluster-based aluminum material as iodine adsorbents.