Heterostructure ZIF-8@MXene with sieving effect in mixed matrix membranes for CO2 separation

At the present time, the realm of gas separation membranes is predominantly centered on the development of membrane materials that simultaneously exhibit exceptional gas permeability and selectivity. Mixed Matrix Membranes (MMMs) hold significant promise in addressing the long-standing challenge of balancing membrane selectivity with permeability. By incorporating a molecular sieving mechanism, an enhanced gas separation process is achieved. In this research endeavor, single-layer MXene nanosheets serve as an ideal substrate for the direct growth of ZIF-8 nanoparticles, yielding heterogeneously structured nanofillers, coined ZIF-8@MXene. The composite filler, ZIF-8@MXene, maintains a two-dimensional lamellar structure reminiscent of MXene, while also integrating ZIF-8 nanoparticles with their optimal pore size of 3.4 Å. This optimal pore size efficiently facilitates the unimpeded passage of CO 2 molecules through the channels, creating a preferential pathway. Conversely, N 2 molecules encounter greater difficulty traversing these channels, effectively coupling the solubility-diffusion mechanism with the molecular sieving mechanism to enhance selectivity in gas separation processes. Consequently, the mixed matrix membrane exhibits a remarkable enhancement in gas selectivity. Particularly, under sub-ambient conditions (−20 °C), the PEO/ [email protected]  % membrane achieves an exceptional CO 2 /N 2 selectivity of 294.1, accompanied by a high CO 2 permeability of 115.58 Barrer. This outstanding performance surpasses the 2019 upper bound, underscoring the significant potential of heterostructured nanofillers to be harnessed in advancing various mixed matrix membranes (MMMs) towards high-performance gas separation capabilities.