Lability of Hydrogen-Bonded Organic Framework (HOF) Crystals: A Deep Insight into the Structure–Stability Relationship

Ever since the inception of research on hydrogen-bonded organic framework (HOF) materials, their poor framework stability has been a persistent challenge, which has severely hampered the application of HOFs. To date, the elaborate and deep association between the structure–stability relationship of HOFs is still not well understood. In this work, a novel HOF crystal THOF-1 featuring a hexagonal pore was constructed from N¹, N³, N⁵-tris(pyridin-3-yl) benzene-1,3,5-tricarboxamide. Compared with the reported HOF-8, which was built from N¹, N³, and N⁵-tris(pyridin-4-yl) benzene-1,3,5-tricarboxamide, THOF-1 exhibited weaker stability. Specifically, THOF-1 would transform to THOF-H₂O with a tightly packed crystal structure in air or could directly collapse upon solvent removal from its pores. Motivated by the striking stability discrepancy between THOF-1 and HOF-8, a series of comparison studies including Hirshfeld surface analysis, supramolecular synthon analysis, IGMH analysis, crystal energy framework analysis, and MESP analysis were carried out to rationalize this phenomenon. This work aims to give a deep insight into the structure–property relationship of HOF crystals, thereby offering valuable guidance for the rational design and fabrication of stable HOF materials.