Unraveling Energy Transfer Dynamics and Exciton Diffusion in Multicomponent Metal–Organic Frameworks

Abstract

Luminescence in metal–organic frameworks (MOFs) typically has one of three fundamental origins: emission from ligands, metal clusters, and encapsulated guests. Photophysical processes such as energy transfer or charge transfer can further modulate the emission profile. However, as the MOF structure becomes more complex, it can become increasingly difficult to pinpoint the origin of the emission. Herein, we report on the energy transfer behavior of multicomponent zinc-based frameworks from the MUF-77 family, which combine three luminescent, aromatic ligands and Zn₄O nodes. Each ligand has distinct photophysics and energy transfer behavior upon photoexcitation. Time-resolved photoluminescence spectroscopy on the nanosecond and picosecond time scales reveals the specific interligand energy pathways that influence the emission profile. Fluence-dependent measurements uncover both bimolecular and higher-order recombination in MUF-77. The long lifetimes and low bimolecular recombination rate point to modest exciton diffusion alongside higher-order exciton-charge annihilation in these systems.