431787 a highly permeable and selective aminofunctionalized MOF CAU-1 membrane for separation of molecular mixture

Metal-organic frameworks are appealing candidates for molecular separation particularly for CO₂ and other molecular mixture separation because of the high porosity, structural flexibility, pore size and chemical tailorability as highlighted in several reviews.^1-5 In the form of powders, MOFs have exhibited an unprecedented CO₂ adsorption capacity/selectivity and high CO₂ adsorptive separation efficiency from N₂ and CH₄. The excellent preferential CO₂ adsorption ability are expected to lead to high CO₂ permselectivity over other gases for MOFs membranes. However, so far only the MOF-5 membrane reported by Zhao et al. showed efficient separation for CO₂/N₂ mixtures under high pressure and CO₂ content conditions.^6-7 Instead, other reported MOFs membranes including small and large pore size MOFs membranes have so far shown a poor CO₂/N₂ separation selectivity around 1 for either single gas or mixture system despite of their high adsorption selectivity.^8-11 There is a long way to explore MOF membranes with high performance for CO₂ capture. In the present work, a continuous and thin amine-decorated microporous metal-organic framework CAU-1 membrane on asymmetric a-Al₂O3 support was synthesized and explored for CO2 separation. The obtained CAU-1 membrane was of 2C3μm thin and exhibited a high CO2 permeance of up to 1.34 °Á 10-6 mol m^-2 s^-1 Pa^-1 and a CO₂-N₂ selectivity of 17.4-22.8 for CO₂-N₂ mixtures, demonstrating for the first time that aminofunctionalized MOF membranes can provide high CO2CN2 selectivity and possess the potential for CO2 capture from flue gas¹². Separation of other molecular mixture will be studied as well.