  Directly imaging the configurations of small molecules at the ambient
temperatures will greatly promote the study of their chemical and physical
properties, including the host-guest interactions of organics in porous
materials during the adsorption, catalysis and energy storage. However, due to
the current challenges on the small-molecule imaging by the (scanning)
transmission electron microscopy ((S)TEM), we still have a lack of the
molecular-level understandings on the host-guest interactions and other
molecular behaviors. Here, we achieved the STEM imaging of various small
aromatics confined in the MFI-type zeolite frameworks by using the integrated
differential phase contrast (iDPC) technique. Due to the strong confinement
effect in MFI channels, the 1D solid-like aromatic columns showed the coherent
configurations, which were clearly resolved by enhancing the host-guest
interactions. Then, we also evaluated the strength of host-guest interactions
directly by the image analysis and revealed the desorption behaviors of
confined aromatics during the in-situ heating process. These results not only
helped us to reveal the configurations and host-guest interactions of small
aromatics during the adsorption/desorption in porous materials, but also
expanded the applications of STEM to further study other molecular behaviors in
the real space.
