Incorporating KAUST-7 into PIM-1 towards mixed matrix membranes with long-term stable CO2/CH4 separation performance

Rational design of fillers and polymers is of great importance to fabricate mixed matrix membranes (MMMs) with high performance. In this work, fluorinated metal-organic frameworks (KAUST-7 (also referred as NbOFFIVE-1-Ni)) were adopted as nanofillers to prepare MMMs through physically blending into the polymer of intrinsic microporosity (PIM-1). Benefiting from the features of porous KAUST-7, including well CO2 affinity, distinctive pore characteristics (size, shape, and functionality) and strong intermolecular interactions with PIM-1, the achieved MMMs demonstrated increased CO2/CH4 separation performance and improved anti-physical aging property. Specifically, with the assistance of KAUST-7, the CO2 permeability and CO2/CH4 (30:70 vol%) selectivity of the optimized MMMs increased up to 5928 Barrer and 23.5, corresponding to improvements of 50% of and 88% of the permeability and selectivity compared with the pristine membranes, respectively. Importantly, 100-h continuous separation test results confirmed the satisfying long-term stability of the prepared MMMs. Notably, the MMMs maintained 91% of the initial CO2 permeability after 150 days (decreased only 539 Barrer), implying that the CO2 permeability decrement is about 5-fold lower than that of the control PIM-1 membrane. These results suggest that the fabricated MMMs are promising candidates for CO2 separation in practical applications.