Multidimensional supramolecular assemblies based on cucurbit[n]uril (n = 6 or 7) were constructed via the outer-surface interactions of cucurbit[n]urils with the polyaromatic compound 4,4',4"-benzene-1,3,5-triyl-tribenzoate as a structure-directing agent. Most impressively, the cucurbit[6]uril-based assembly exhibits high selectivity for capture of cesium cations among the common alkali metal ions in a basic medium and releases the cesium cations under acidic conditions. This reversible process enables possible applications in cesium cation capture.