Mixed Matrix Membrane with Fluorinated MIL-101(Cr) Filler for the Separation of CO 2 and CH 4

Mixed matrix membranes (MMMs) incorporating metal–organic frameworks (MOFs) are attractive for molecular recognition and separations, but precisely engineering the MOF filler structure toward maximizing its inherent nanopore separation capability remains challenging. Here, we report a fluorination strategy to functionalize MIL-101 that synergistically optimizes its pore chemical environment and interfacial compatibility with the polymer matrix. Compared with the MIL-101/6FDA-DAM membrane, the incorporation of strong electron-withdrawing fluorinated ligands enhances both the CO2 adsorption affinity of MIL-101 and its hydrogen-bonding interaction with the 6FDA-DAM matrix. The optimized MIL-101-F/6FDA-DAM (10 wt %) membrane achieves a CO2 permeability of 2200 Barrer, a 150% enhancement over the pure 6FDA-DAM membrane, while maintaining a comparable CO2/CH4 selectivity of 21. The excellent separation performance surpasses the 2008 Robeson upper bound. This work provides a simple and effective approach to advancing the gas separation performance of MMMs.