Pebax-based mixed matrix membranes derived from microporous carbon nanospheres for permeable and selective CO2 separation

Abstract

We investigated the use of microporous carbon nanospheres (CNs) as fillers to prepare mixed matrix membranes (MMMs) for permeable and selective CO2 separation. CNs with a uniform size of 650 nm and unique amorphous structure were characterized by SEM and XRD. The N content of CNs with different carbonization temperatures was determined by XPS. The surface area and micropore size of the samples could be easily adjusted by varying the carbonization temperature; in particular, increasing the carbonization temperature improved both parameters. At 600 °C, the particles (CNs-600) exhibited a higher N content and narrower micropores, which ensured higher affinity and enhanced capture of CO2 molecules. Thus, CNs-600/Pebax MMMs exhibited superior CO2 separation performances compared to other CNs-based MMMs. Furthermore, when the loading of CNs-600 was 0.5 wt%, the MMMs exhibited the best CO2/N2 separation properties, with a 39.51% improvement compared to pristine Pebax membranes. These outstanding performances are attributed to the fact that microporous CNs with accessible inner channels can provide a low-resistance transport pathway to gas molecules. Moreover, the strong interaction between CO2 and the pore walls, along with the high N content, enabled an effective separation of CO2 from other gas molecules. Importantly, the CNs-600/Pebax MMMs displayed superior CO2/N2 selectivity compared to previously reported Pebax-based MMMs with other fillers. The proposed CNs, with microporous structure and high N content, may represent a promising alternative for the fillers of MMMs.