Endohedral fullerenes are formed by placing atoms or clusters in empty fullerene cages. Among them, magnetic endohedral metallofullerenes with unpaired electron spin have attracted many interests due to their potential application in quantum information processing (QIP), high-density data storage, and magnetoreception system. Notably, the arrangement of these magnetic endohedral fullerenes in solid state is essential for further applications. The metal-organic frameworks (MOFs) have been intriguing many interests due to their porous structures and excellent crystallinity. Particularly, the ordered nano-sized pores in MOF crystals make them good host for these metallofullerenes. In previous report of fullerene-containing host-guest complex, the fullerene carbon cages are always prone to interact with the planar aromatic motif of the host molecules through strong π-π interactions. In MOF structures, there are many similar planar aromatic contents. For example, MOF-177 has cage-shaped pore with two sets of parallel quasi-planar triphenylbenzene unit, 1.4 nm apart from each other. Therefore, the MOF-177 can well accommodate metallofullerenes and the ordered pores of MOF would lead to special solid state magnetic system.

Herein, we report the preparation and magnetic property of metallofullerenes (Y₂@C₇₉N, Sc₃C₂@C₈₀, and DySc₂N@C₈₀) accommodating in MOF-177 crystal through a bottom-up approach. In Y₂@C₇₉N@MOF-177 complex, the Y₂@C₇₉N molecules tend to reside along the c-axis of MOF-177 crystal lattice under low temperature as disclosed by its axisymmetric electron spin resonance (ESR) characters. The confined effect of MOF’s pores plays a significant role in steering the electron spin on endohedral fullerene, leading to anisotropic paramagnetic solid system. In Sc₃C₂@C₈₀@MOF-177 complex, it was disclosed that the ESR signals of Sc₃C₂@C₈₀ can sense the tiny transformation of flexible pores under external stimuli. Furthermore, the changes of MOF-177 pores under different conditions exhibit reversible process as shown by Sc₃C₂@C₈₀ EPR signals, which demonstrates the breathing of MOF-177 frameworks. In DySc₂N@C₈₀@MOF-177 complex, the magnetic properties of DySc₂N@C₈₀ can be effectively altered by means of imprisoning the molecule in MOF-177. Typically, its quantum tunnelling of magnetism (QTM) is suppressed through spin-phonon couplings.