Hydrolysis Kinetics-Induced Stability Enhancement of Activated Formate-Based MOFs under Dynamic Vapor Flow

The ubiquitous presence of water vapor represents a critical challenge for the practical implementation of metal-organic frameworks (MOFs). Although the water stability of some MOFs has been studied, existing stability tests were rarely conducted under industrial relevant dynamic conditions. We therefore systematically compared the water stability of commercially available <i>α</i>-Mg₃(HCOO)₆ MOF and isostructural <i>α</i>-M₃(HCOO)₆ (M = Mn, Co, Ni) MOFs. All MOFs rapidly transformed to dense M(HCOO)₂·2H₂O when in contact with liquid water. The transformation is considerably slower in water vapor, following a stability order of Ni > Mg ≈ Co > Mn. Notably, activated MOFs exhibited higher stability than as-made MOFs under dynamic water vapor flow, while their stabilities are comparable under static water vapor. We conclude that such hydrolysis stability enhancement is due to the kinetic effect: weakly adsorbed water molecules are rapidly removed in dynamic vapor flow when channels are open, resulting in delayed hydrolysis. These findings show that even MOFs, which are thermodynamically prone to hydrolysis, can retain their functionality in dynamic vapor flow, providing valuable guidance for the industrial application of MOFs.