Cucurbit[n]urils (Q[n]) are promising ligands for the coordination of metal ions, metal complexes or clusters, and form various Q[n]-based complexes. Among the Q[n] complexes, those formed by direct coordination between Q[n]s and metal ions are particularly important. The direct coordination of metal ions to cucurbit[n]urils leads to the formation of Q[n]-based molecular capsules, tubular polymers and molecular bracelets, which could have nanoscale applications in drug delivery, molecular devices and new materials. Cucurbit [n] urils (Q [n]) are promising ligands for the coordination of metal ions, metal complexes or clusters, and form various Q [n] -based complexes. The direct coordination of metal ions to cucurbit [n] urils leads to the formation of Q [n] -based molecular capsules, tubular polymers and molecular bracelets, which could have nanoscale applications in drug delivery, molecular devices and new materials.