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 H 2 /CH 4 , from 2.9 to 38 for CO 2 /CH 4 , from 2.4 to 29 for CO 2 /N 2 , from 2.9 to 8 for O 2 /N 2 , after Mn(acac) 2 treatment at 175°C for 30 min. Stable equimolar propylene/propane mixture selectivity of 168 at ambient temperature, and 4 bar equimolar feed with a propylene flux of 8.3 x 10 -3 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.