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

Abstract

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 ∼10 2 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 C 60, 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 C 60 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-C 60 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.

Topics & Concepts