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. ZIF‐8 membrane separation performance is modified by a facile vapor‐phase metal–organic treatment. Significant increase in selectivity for propylene/propane and hydrogen over other gases is demonstrated at the expense of reduced flux.