The nanoconfinement effect defined by the polyoxometalate nanocage renders the encapsulated bulky ligands rigid properties by significantly limiting and slowing down their diffusive motions. These ligands that partially cover the interfacial pore on the molybdenum oxide shells are able to block some large guest molecules from going inside the capsule cluster, which provides a convincing protocol for size-selective encapsulation and separation. More information can be found in the Communication by P. Yin et al. on page 14131 ff.