ZIF‐8 Membrane Permselectivity Modification by Manganese(II) Acetylacetonate Vapor Treatment

Vapor-phase treatment of ZIF-8 membranes with manganese(II) acetylacetonate (Mn(acac)₂ ) allows permselectivity tuning. Propylene/propane selectivity increases from 31 to 210 after the Mn(acac)₂ treatment at 165 °C for 30 min, while selectivities increase from 14.6 to 242 for H₂ /CH₄ , from 2.9 to 38 for CO₂ /CH₄ , from 2.4 to 29 for CO₂ /N₂ , and from 2.9 to 7.5 for O₂ /N₂ , after Mn(acac)₂ treatment at 175 °C for 30 min. Stable equimolar propylene/propane mixture selectivity of 165 at ambient temperature and 4 bar equimolar feed with a propylene flux of 8.3×10^-4 mol m^-2 s^-1 is established. A control experiment excludes thermal treatment alone causing these changes. XPS analysis reveals the presence of Mn(acac)₂ on the outer surface of the vapor-treated ZIF-8 membranes while no other changes are detectable by X-ray diffraction and infrared spectroscopy.