Emerging mechanically interlocked cages

Mechanically interlocked molecules, including catenanes, rotaxanes and knots, are an intriguing class of synthetic targets with potential applications in molecular switches and machines. Although mechanically interlocked molecules are typically constructed using macrocyclic frameworks, the interlocking of two or more three-dimensional, shape-persistent cages remains relatively underexplored. Recent advances have accelerated the development of mechanically interlocked cages (MICs), which consist of interlocked three-dimensional molecular cages rather than macrocycles. Despite their potential in areas such as molecular recognition, separation and catalysis, the design and synthesis of MICs remain challenging. This Review examines the synthetic strategies used to construct MICs, along with their interlocked architecture characteristics, structural dynamics and potential applications. Special attention is given to the guest-binding properties and catalytic performance of monomeric versus catenated cages. We conclude with perspectives on the current challenges and opportunities for future development of MICs.