Chemical Stability of MIL-101(Cr) upon Adsorption of SO 2 and NO 2 under Dry and Humid Conditions

A detailed understanding of the chemical stability of metal–organic frameworks (MOFs) in water and acidic and basic solutions currently exists; however, there has been comparatively little investigation into the chemical stability of MOFs in the presence of acid gas species that may be present in industrial settings. MIL-101(Cr), a MOF that is stable in liquid water as well as acidic and basic solutions, was tested for its stability upon exposure to the acid gases sulfur dioxide (SO2) and nitrogen dioxide (NO2). Successive breakthrough experiments of both SO2 and NO2 show that both gases lower the adsorption capacity of MIL-101(Cr), which is also observed by N2 physisorption experiments. X-ray photoelectron spectroscopy (XPS) confirms the presence of sulfur and nitrogen species in MIL-101(Cr) after exposure to SO2 and NO2 species. In situ infrared spectroscopy experiments 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 what has been previously observed in HKUST-1.