Perfluorinated Nanoporous Metal–Organic Framework-Based Mixed-Matrix Membranes for CO₂ Capture

The combination of perfluoropolymers with perfluorinated metal–organic frameworks (MOFs) can play an important part in the development of mixed-matrix membranes (MMMs) for the capture of CO 2, thanks to the enhanced selectivity toward CO 2 and resistance to humidity. Herein, we report the incorporation of the perfluorinated nanoporous MOF F4_MIL-140A(Ce), based on Ce IV and tetrafluoroterephthalate, into one of the most representative perfluoropolymers in membrane science, i.e., Hyflon®AD60X, to form a MMM containing 20 wt % of the MOF filler for the separation of CO 2 from N 2 and CH 4 . The membrane was characterized by solid-state nuclear magnetic resonance (NMR) spectroscopy, infrared spectroscopy (IR), and gas sorption analysis, finding that the MOF retains its peculiar cooperative mechanism of CO 2 adsorption even when embedded in the polymeric matrix. Pure-gas permeation tests on the MMM confirmed the enhancement of selectivity for CO 2 /N 2 and CO 2 /CH 4 gas mixtures, with nonvirtual reduction in permeability. The incorporation of F4_MIL-140A(Ce) into Hyflon®AD60X enhances the CO 2 /CH 4 selectivity from 9.1 to 14.3 and from 6.2 to 7.7 for CO 2 /N 2 separation. The CO 2 permeabilities are slightly reduced by less than 5% from 304 to 290 Barrer. Adsorption isotherms, combined with IR and solid-state NMR spectroscopy measurements, suggested that the MMM behavior can be ascribed to the peculiar CO 2 adsorption mechanism of F4_MIL-140A(Ce), which is retained even when the MOF is embedded in the polymer matrix.