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.