【正文】 defined as resistance of the structure to degradation. However, another possible definition is thermodynamic in origin: many functionally stable MOFs (as well as zeolites) are thermodynamically unstable with respect to alternative — typically, denser — polymorphs. An active area of MOF research is the development of routes to thermodynamically unstable, but functionally stable, polymorphs. Chemical stability 1 2 Thermal stability 3 Hydrothermal stability 4 Mechanical stability Stability of metal–anic frameworks 1 Chemical stability The greatest concerns for the improvement of MOF chemical stability have been largely related to liquid water and water vapour。 accordingly, we focus on aqueous solutions. In most MOF structures, the chemical weak points are at the nodes — more specifically, the metal–linker bonds — with hydrolysis yielding a protonated linker and a hydroxide(or water) ligated node. Acidic solutions can accelerate the formation of the former, and basic solutions can accelerate the formation of the latter. Although there is no standard method for assessing the stability of MOFs in acidic, basic or neutral solutions, it is often judged by paring the powder Xray diffraction (PXRD) pattern of a MOF before and after soaking it in a given aqueous solution. The chemical (acid–base) stability of some representative metal–anic frameworks based on literature data. The bar length indicates the pH range that the metal–anic framew