Highly permeable MOF NH2-MIL-101(Cr) fragment membranes for CO2/N2 separation

Abstract

Metal-organic framework (MOF) membranes with proper pore size distribution and functional groups are generally more suitable for separation. Most MOFs are characterized by a hierarchical pore structure, which possesses large cavities surrounded by small windows. Fabrication of MOF membranes only retaining microporous fragment structure is a workable method to narrow pore size distribution. In this study, well-grown NH₂-MIL-101(Cr) fragment membranes were fabricated for CO₂ separation by adjusting acetic acid – ligand – metal ratio to balance the nucleation and growth. NH₂-MIL-101(Cr) fragment has a similar chemical structure to NH₂-MIL-101(Cr) as expected, but only small pores with size around 0.56 nm is retained. The NH₂-MIL-101(Cr) fragment membranes exhibited CO₂/N₂ selectivity of about 37 with CO₂ permeance up to 6104 GPU.