Ce-doped ZnO@ZIF-8 core-shell nanotube mixed matrix membranes for CO2 separation

In this study, the morphology of ZnO was altered from nanofibers to hollow nanotubes by Ce doping, mainly owing to the Kirkendall effect originating from different diffusion rates of constituent elements. A novel one-dimensional core-shell nanotube (ZnO-CeO 2 @ZIF-8) was successfully fabricated, characterized by a distinctive structure comprising a ZIF-8 shell and a ZnO-CeO 2 nanotube core. The as-prepared ZnO-CeO 2 @ZIF-8 exhibited a large specific surface area, substantial pore volume, and strong affinity towards CO 2 . These ZnO-CeO 2 @ZIF-8 were integrated into Pebax-1657 to construct MMMs for high-efficiency CO 2 transport and separation. Furthermore, the unique 1D hollow structure of the filler effectively reduced the resistance to mass transfer and enhanced gas permeability, while the ZIF-8 shell and Ce-induced oxygen vacancies synergistically enhanced the CO 2 adsorption and selectivity. The Pebax/ZnO-CeO 2 @ZIF-8 MMMs containing 3 wt% loading demonstrate superior performance, characterized by a CO 2 permeability of 94.0 Barrer and CO 2 /N 2 selectivity of 64.8 respectively. Compared to the unmodified Pebax, these values exhibit enhancements of 73.4% and 36.7%, suggesting that ZnO-CeO 2 @ZIF-8 holds considerable promise in the realm of MMMs for adsorption and separation of CO 2 .