Mixed matrix membranes (MMMs) fabricated via ultrathin Cu-MOF nanosheets for CO2/N2 separation: Low loading but high performance

• Novel 2D Cu-MOF nanosheets with thickness of ∼20 nm synthesized;. • 2D Cu-MOF exhibited special layer stacking structure. • Presence of 2D Cu-MOF simultaneously improved both CO2 permeability and CO2/N2 selectivity;. • 0.2 wt% 2D Cu-MOF addition leads to CO2 permeability of 619.1 Barrer and CO2/N2 selectivity of 23.89;. • Obtained MMMs also presented excellent long-term stability. Emerging two-dimensional metal-organic frameworks (MOFs) were widely utilized in the fabrication of mixed matrix membranes (MMMs) for CO 2 /N 2 separation, owing to their high specific surface area, high aspect ratio, layered structure, and nanoscale thickness. In the current work, a novel Cu-MOF nanosheet with an approximate thickness of ∼20 nm has been synthesized for the first time and used as nanofillers to fabricate MMMs with Pebax 2533. In the MMMs, these Cu-MOF nanosheets could self-assemble into a unique stacked configuration within the Pebax matrix, facilitating rapid CO 2 transport while extending the transport path for N 2 , thereby enhancing both CO 2 permeability and CO 2 /N 2 selectivity of the obtained Pebax-Cu-MOF MMMs. Furthermore, the high aspect ratio of the Cu-MOF nanosheets promotes good interaction with Pebax, thereby improving interfacial compatibility. Under conditions of 2 bar and 35 °C, the CO 2 permeability and CO 2 /N 2 selectivity of the Pebax-Cu-MOF 0.2 wt.% MMM was 619.1 Barrer and 23.89, respectively, representing increases of 231.6 % and 112.4 % compared to pure Pebax. The MMMs also demonstrated excellent long-term stability. These novel Cu-MOF nanosheets exhibit significant potential for applications across a wide range of fields.