Ultra-small defect-engineered UiO-66 on cellulose nanocrystal template for advanced carbon dioxide capture membrane

Abstract

Global warming and associated climate change, primarily driven by greenhouse gas emissions, are no longer a forecast but are now undeniable realities. Although membrane technology presents a highly cost-effective approach for carbon dioxide (CO₂) capture, further research is required to overcome the inherent trade-off between selectivity and permeability to achieve enhanced performance. A novel defect-engineered ultrasmall cellulose nanocrystal (CNC)-templated UiO-66 MOF (CNC-UiO-66 hybrid) was synthesized to improve the performance of Pebax membranes. The elongated geometry of the CNC-UiO-66 hybrid creates extended facilitated transport channels for CO₂, while the highly defective structure, induced by the presence of CNC during synthesis, enhances coordination interactions with both CO₂ and the polymer matrix. As a result, Pebax incorporated with CNC-UiO-66 demonstrated increased crystallinity and thermal stability. The incorporation of as little as 1 wt% of the CNC-UiO-66 hybrid into Pebax membranes achieved a remarkable CO₂ permeability of 1442 Barrer and a selectivity of 40, surpassing the Robeson upper bound (2008) for CO₂/N₂ separation. Cost analysis suggested that this membrane could reduce carbon capture costs to 62 USD per tonne, 10 USD less than conventional membranes. These results highlight the potential of CNC-UiO-66 hybrid membranes for efficient and cost-effective CCUS applications, particularly in flue gas treatment.