PIM-1-based membranes mediated with CO2-philic MXene nanosheets for superior CO2/N2 separation

Membrane gas separation technologies have emerged as highly prospective avenues for the selective separation of CO2. In this research, a novel array of mixed-matrix membranes (MMMs) was engineered, integrating two-dimensional nanosheets of MXene, specifically Ti3C2Tx, into polymers of intrinsic microporosity (PIMs) to selectively separate CO2 from N2. The inclusion of Ti3C2Tx nanosheets, rich in polar functional groups, significantly increases the affinity between CO2 molecules and the fabricated MMMs. Additionally, the precise modulation of the molecular diffusion channels for CO2 and N2 is achievable due to the interlayer spacing between MXene layers (∼0.35 nm) within the PIM-1 matrix. This innovation is predicated on the synergistic effect of solution-diffusion and molecular sieving mechanisms that underpin the gas separation process, leading to a marked improvement in both selectivity for CO2 over N2 and the permeability of CO2. Among the series, the MMMs with a 0.5 wt% MXene display exceptional separation efficiency, achieving a CO2 permeability of 12475.3 barrer and a CO2/N2 selectivity of 32.7. Notably, all the PIM-1/MXene membranes prepared with different compositions in this study exceed the Robeson upper bound defined in 2019, indicating their substantial promise for CO2 separation and capture in industrial applications.