Kinetic stability of metal–organic frameworks for corrosive and coordinating gas capture

Metal–organic frameworks (MOFs) have diverse applications involving the storage, separation and sensing of weakly interacting, high-purity gases. Exposure to impure gas streams and interactions with corrosive and coordinating gases raises the question of chemical robustness; however, the factors that determine the stability of MOFs are not fully understood. Framework materials have been previously categorized as either thermodynamically or kinetically stable, but recent work has elucidated an energetic penalty for porosity for all these materials with respect to a dense phase, which has implications for the design of materials for gas storage, heterogeneous catalysis and electronic applications. In this Review, we focus on two main strategies for stabilization of the porous phase — using inert metal ions or increasing the heterolytic metal–ligand bond strength. We review the progress in designing robust materials for the capture of coordinating and corrosive gases such as H2O vapour, NH3, H2S, SO2, nitrogen oxides (NOx) and elemental halogens. We envision that the pursuit of strategies for kinetic stabilization of MOFs will yield increasing numbers of robust frameworks suited to harsh conditions and that short-term stability towards these challenging gases will be predictive of long-term stability for applications in less demanding environments. Metal–organic frameworks, when evacuated, are metastable with respect to a dense phase of the same components. Here, we review methods for kinetic stabilization of the porous phase and discuss progress in designing stable frameworks for the capture of corrosive and coordinating gases.