Chemical Stability of MIL-101(Cr) upon Adsorption of SO₂ and NO₂ under Dry and Humid Conditions

A detailed understanding of the chemical stability ofmetal-organicframeworks (MOFs) in water and acidic and basic solutions currentlyexists; however, there has been comparatively little investigationinto the chemical stability of MOFs in the presence of acid gas speciesthat may be present in industrial settings. MIL-101-(Cr), a MOF thatis stable in liquid water as well as acidic and basic solutions, wastested for its stability upon exposure to the acid gases sulfur dioxide(SO2) and nitrogen dioxide (NO2). Successivebreakthrough experiments of both SO2 and NO2 show that both gases lower the adsorption capacity of MIL-101-(Cr),which is also observed by N-2 physisorption experiments.X-ray photoelectron spectroscopy (XPS) confirms the presence of sulfurand nitrogen species in MIL-101-(Cr) after exposure to SO2 and NO2 species. In situ infrared spectroscopyexperiments suggest that adsorption of SO2 in MIL-101-(Cr)is not completely reversible and that adsorption of NO2 in MIL-101-(Cr) causes some structural degradation similar to whathas been previously observed in HKUST-1.