Hydrophobic metal–organic framework UiO-66-(CF3)2/PIM-1 mixed-matrix membranes for stable CO2/N2 separation under high humidity

The use of metal–organic frameworks (MOFs) in gas separation has been widely explored. However, the stabilities are poor in various practical applications, especially under humid conditions. In this work, water-stable UiO-66-(CF3)2 was prepared by grafting with trifluoromethyl groups. On this basis, mixed matrix membranes (MMMs) containing different UiO-66-(CF3)2 loadings in PIM-1 were fabricated. When the UiO-66-(CF3)2 loading was increased from 0 to 8 %, the CO2 permeability of the membrane increased from 3265 to 5242 Barrer, and the CO2/N2 selectivity improved from 24.2 to 33.8. Meanwhile, we prepared the PIM-UF/PDMS/PSf (PUPP) composite membranes and applied for CO2/N2 separation under humid conditions. Specifically, PUPP-8 % exhibited a permeability of 1111 GPU and a competitive CO2/N2 separation factor of 43.78 under the simulated flue gas environment (57 °C, 0.1 MPa, 10 vol% H2O), which transcended the 2008 upper bound. Finally, we studied the long-term gas permeability to simulate the real flue gas environment, and the PUPP-8 % water content test conditions maintained its structure and performance, benefiting from good water stability. These results demonstrated that improving the water stability of MOFs and developing high-performance membranes for stabilization in high-humidity environments is a potentially effective strategy.