Macrocycle‐Mediated <scp>3D</scp>‐to‐<scp>2D</scp> Structural Transformation of a Metal−Organic Framework through Coordination Bond Rearrangement

Comprehensive Summary Structural transformation of metal−organic frameworks (MOFs) involving significant rearrangement of coordination bonds represents a powerful strategy to construct novel structures with distinct functionalities. While such transformations are typically driven by solvent, ion, or heat stimuli, the potential of functional macrocycles to trigger framework reconstruction remains unexplored. Herein, we disclose the first macrocycle‐mediated dimensional reduction of a MOF, where the introduction of cucurbit[6]uril (CB[6]) induces 3D‐to‐2D structural transformation through a dissolution‐recrystallization mechanism. This transformation involves the breakage and reformation of coordination bonds and the incorporation of CB[6] within the framework through multiple outer‐surface interactions. The resultant 2D layered framework (CB[6]@Zn‐TCA‐L) demonstrates enhanced stability in aqueous solutions, attributed to the ordered arrangement of CB[6] macrocycles with the encapsulation of Me 2 NH 2 + cations in their cavities. Furthermore, the combination of its 2D layered structure featuring accessible Lewis acidic metal sites and abundant active sites on the CB[6] surface enables CB[6]@Zn‐TCA‐L to function as a highly efficient catalyst for the cycloaddition of CO 2 with various epoxides under mild conditions.