Synthesis and Crystal Structure of a New Chiral Hydrogen-Bonded Organic Framework ZIOC-2

A new chiral hydrogen-bonded organic framework (HOF) ZIOC-2 was synthesized using an optically active building block, namely, l-prolineamide-substituted diarylacetylenedicarboxylic acid (4,4′-ethyne-1,2-diyl-bis[3-(l-prolylamino) benzoic acid], EDPABA). Self-assembly of EDPABA in aqueous medium results in the crystallization of either sesquihydrate ZIOC-2 1.5H2O or tetrahydrate ZIOC-2 4H2O. The latter tetrahydrate form can be irreversibly transformed into the sesquihydrate one under heating up to 35 °C. The full dehydration of the sesquihydrate form occurs at 150 °C in open air and at 220 °C, when the sample was placed into a sealed capillary. The anhydrous crystalline form, denoted as ZIOC-2, remains intact upon heating up to 225 °C. Crystal structures of the synthesized novel materials were established with the use of X-ray powder diffraction data. The structural examinations have shown that the ZIOC-2 framework can reversibly absorb and desorb water molecules. The potential application field of the novel HOF material can be related to the absorption from liquid and gas phases.