Spin crossover in metal–organic cages

Spin-crossover (SCO) materials, as stimulus-responsive molecular switches, have garnered significant attention for applications in information storage, biomimetic sensing, and molecular devices due to their unique ability to couple magnetic bistability with external stimuli (e.g. temperature, pressure, light, and electric field). In recent years, spin-crossover metal–organic cages (SCO-MOCs) have emerged as the nexus of chemical synthesis, supramolecular engineering, and quantum science. These systems integrate spin-state switching with molecular functionality, offering tuneable topological architectures, distinctive SCO characteristics, and dynamic host–guest responsiveness. This frontier paper highlights recent advances in Fe(II)/Fe(III)-based coordination cages over the past decade, with a systematic overview of strategies for optimizing SCO behavior through coordination microenvironment engineering and supramolecular assembly. Emphasis is placed on ligand field modulation and spatial confinement effects, along with analyses of guest encapsulation mechanisms. The potential application of SCO-MOCs in areas such as targeted drug delivery and sensing platforms are discussed. Finally, perspectives on future research directions are outlined, underscoring the transformative potential of SCO-MOCs in next-generation smart materials and quantum-enabled technologies.