Solvent-Directed Assembly of π-Stacked 3D Metal–Organic Frameworks with Tunable Conductivity Enhanced by C60 Encapsulation

Metal-organic frameworks (MOFs) with tunable structures and unique host-guest chemistry have emerged as promising candidates for conductive materials. However, the tunability of conductivity and porosity in conductive MOFs, as well as their interrelationship, still lacks a systematic study. Herein, we report the synthesis of a series of 3D copper MOFs (NU-4000 to NU-4003) using a triphenylene-based hexatopic carboxylate linker. By modulating the ratio of mixed solvents, distinct structural topologies and π-π stacking arrangements were achieved, resulting in electrical conductivities ranging from insulators (<10^-6 S/cm) to semiconductors (10^-8∼10² S/cm). Among them, NU-4003 features continuous π-π stacking and exhibits a conductivity of 1.7 × 10^-6 S/cm. To further enhance the conductivity, we encapsulated C₆₀, a strong electron acceptor, within the circular channels of NU-4003, resulting in a remarkable conductivity increase to 140 S/cm with approximately 100% pore occupancy. Even at lower C₆₀ loadings that leave 54% of the pore volume accessible, the conductivity remains exceptionally high at 104 S/cm. This represents an eight-order magnitude enhancement and positions NU-4003-C₆₀ as one of the most conductive 3D MOFs reported to date. This work integrates two charge transport pathways (through-space and electron donor-acceptor interactions) into a single MOF host-guest material, achieving a significant enhancement in conductivity. This study demonstrates the potential of combining host-guest chemistry and π-π stacking to design conductive MOFs with permanent porosity maintained, providing a blueprint for the development of next-generation materials for electronic and energy-related applications.