Constructing MOF-based mixed matrix membranes with weak polarity for the CH4/N2 separation

The recovery of low-concentration methane is crucial for both energy sustainability and greenhouse gas reduction. Membrane separation is an energy-efficient technology, but it still requires high-performance materials. We developed a novel mixed matrix membrane (MMM) by incorporating weakly polar Cu(INA) 2 nanoparticles into poly(styrene-ethylene-propylene-styrene) (SEPS). This design combined the mechanical strength of the SEPS skeleton with the specific adsorption capability of Cu(INA) 2 , achieving a synergistic effect. The obtained membrane utilized both dissolution-diffusion and adsorption-diffusion separation mechanisms, significantly enhancing CH 4 /N 2 separation performance. The CH 4 /N 2 ideal separation factor of 5 wt% Cu(INA) 2 /SEPS MMM reached 9.3, surpassing the majority of existing reports. Compared with pristine SEPS CH 4 /N 2 separation factor improved by 90%. In the CH 4 /N 2 (5/95, vol%) mixed gas test, the 5 wt% Cu(INA) 2 /SEPS MMM increased the CH 4 concentration from 5 vol% to 14.5 vol% and obtained a CH 4 /N 2 separation factor of 5.6. This work demonstrated an effective strategy for developing high-performance MMMs, which exhibited potential for the purification of low-concentration methane.