Stability and Hydration/Dehydration Mechanisms of a Carboxylate-Containing Metal-Organic Framework

Metal-organic frameworks (MOFs) are promising functional compounds; however, they are known to be moisture sensitive. Here, we investigate the hydration and dehydration processes of the carboxylate-containing MOFs [Ni2(nic)4(H2O)]n (nic = nicotinic acid) and the mononuclear complex [Ni(nic)2(H2O)4], respectively. X-ray single crystal diffraction reveals that the hydrogen bonds between water and carboxylic oxygen play a key role in these processes. Molecular-level mechanisms of reversible hydration and dehydration are proposed, based on the competition between water and carboxylic oxygen for coordination with Ni. This study provides important information for future studies on the hydrolytic stability of MOFs in moisture.