Pore engineering of ZIF-L fillers to boost the carbon capture performance of Pebax-based mixed matrix membranes

The pore engineering of metal–organic frameworks (MOFs) fillers holds significant potential to enhance the gas separation performance of mixed matrix membranes (MMMs). In this work, we applied the topological phase transformation strategy to the pore engineering of fillers for MMMs. By ultrasonic heating ZIF-L in methanol, the phase transformation was realized in 2 h (much faster than previous works, the product denoted as ZL-2), the morphology of ZIF-L is basically preserved, but its porous structure is thoroughly regulated. This enables us to investigate the pure effect of filler porosity on the microstructure and separation performance of MMMs. As revealed by positron annihilation lifetime spectroscopy, pure Pebax membrane exhibits a unimodel porous structure, but ZL-2@Pebax membrane (ZL-2 fillers of 10 wt%) possesses a bimodal porous structure with a higher porosity. This leads to a remarkable improvement of CO₂/N₂ separation on both the permeability (45% increment for CO₂) and selectivity (11% increment) compared to pure Pebax membrane. These findings address the critical importance of pore engineering of MOF fillers for the gas separation performance of MMMs.