Heterogeneous Single-Molecule Diffusion in One-, Two-, and Three-Dimensional Microporous Coordination Polymers: Directional, Trapped, and Immobile Guests

The diffusion of individual Nile red molecules in three different crystalline microporous coordination polymers (MCPs) is visualized with single-molecule fluorescence microscopy. By localizing molecules with high spatial resolution, the trajectories of the diffusing dyes are reconstructed with nanometer-scale precision. A detailed analysis of these tracks reveals different dynamics and guest–host interactions in each crystal as well as distinct motion types within the same system, suggesting the presence of structural heterogeneities in local environments.