Visualizing the Entire Range of Noncovalent Interactions in Nanocrystalline Hybrid Materials Using 3D Electron Diffraction.

Noncovalent interactions are essential in the formation and properties of a diverse range of hybrid materials. However, reliably identifying the noncovalent interactions in nanocrystalline materials remains challenging using conventional methods such as X-ray diffraction and spectroscopy. Here, we demonstrate that accurate atomic positions including hydrogen atoms can be determined using three-dimensional electron diffraction (3D ED), from which the entire range of noncovalent interactions in a nanocrystalline aluminophosphate hybrid material SCM-34 are directly visualized. The protonation states of both the inorganic and organic components in SCM-34 are determined from the hydrogen positions. All noncovalent interactions, including hydrogen-bonding, electrostatic, π-π stacking, and van der Waals interactions, are unambiguously identified, which provides detailed insights into the formation of the material. The 3D ED data also allow us to distinguish different types of covalent bonds based on their bond lengths and to identify an elongated terminal P═O π-bond caused by noncovalent interactions. Our results show that 3D ED can be a powerful tool for resolving detailed noncovalent interactions in nanocrystalline materials. This can improve our understanding of hybrid systems and guide the development of novel functional materials.