Synergistic Effect of Combining Uio-66 Nanoparticles and Mxene Nanosheets in Pebax Mixed-Matrix Membranes for Co2 Separation

The performance of gas separation membranes can be enhanced by mixed-matrix membranes (MMMs), but poor interactions between additives and matrix and the agglomeration of highly incorporated fillers limit the benefits of overcoming tradeoff effect. Therefore, the regulation of the state of fillers in membrane matrix is a crucial indicator in the development of MMMs. In this study, MXene (Ti3C2Tx) nanosheets and UiO-66 nanoparticles were prepared and used as fillers, in combination with a Pepax-1657 matrix, to synthesize MMMs for CO2-gas separation. As-prepared MMMs were used for the separation; the large pores (0.5–0.6 nm) of UiO-66 served as a highway to enhance CO2 permeability, and MXene nanosheets were used as selective channels to achieve high selectivity via the terminal polar surface groups of MXene. The combination of UiO-66 and MXene not only enhanced the selectivity, but also increased the solubility and diffusivity via selective CO2 adsorption and the tortuous pathway provided by MXene nanosheets. As a result, adding MXene and UiO-66 to Pebax helped MMMs overcome the tradeoff effect. MMMs loaded with 10 wt% MXene/UiO-66 exhibited a permeability coefficient of CO2 of 214.6 Barrer and a CO2/N2 selectivity coefficient of 102. Dual filler-containing MMMs showed enhanced CO2 permeability coefficient and CO2/N2 selectivity in comparison to pristine Pebax and individual nanofiller-added membranes. In this study, the combination of 2D MXene and UiO-66 nanoparticles exerted a synergistic effect in improving the CO2 separation efficiency of MMMs. This research provides a novel route for fabricating high-performance MMMs in the separation of CO2.