Design of task-specific ıonic liquid-ıncorporated IL/ZIF-8 composites for high-performance CO2 separation

Abstract

Rising atmospheric CO 2 levels, primarily driven by fossil fuel combustion, necessitate the development of advanced carbon capture technologies. In this study, we investigate the incorporation of a task-specific ionic liquid (TSIL) into the zeolitic imidazolate framework ZIF-8, known for its high thermal stability and molecular sieving properties, to enhance CO 2 separation performance. Among 35,476 screened ionic liquids, guanidinium iodide (GAI) was identified as an optimal candidate and incorporated into ZIF-8. The resulting composites exhibited significantly improved CO 2 adsorption capacity and selectivity. This enhanced gas separation performance was attributed to the strong chemical interactions between CO 2 and the amine-functionalized cation of GAI. Notably, GAI/ZIF-8 composites with 40 and 50 wt % loadings achieved CO 2 /N 2 and CO 2 /CH 4 selectivities of 32.3 and 18.7, respectively, at 1 bar and 25 °C. A trade-off value between selectivity and capacity (TSN) of 208 for CO 2 /CH 4 separation was observed at 50 wt % GAI-loaded composite, while TSN values of 310 and 271 were obtained for CO 2 /N 2 separation at 40 and 50 wt % loadings. Moreover, under dynamic mixed-gas breakthrough conditions, GAI/ZIF-8 composites also exhibit markedly enhanced CO 2 /N 2 separation performance, with significantly delayed CO 2 breakthrough and up to 8.4-fold higher selectivity than pristine ZIF-8. These results demonstrate the potential of TSIL-functionalized ZIF-8 composites for efficient CO 2 separation and highlight the importance of tailoring host–guest interactions to optimize performance.