Integrating two-dimensional MXene fillers into nanocellulose for the fabrication of CO2 separation membranes

To achieve high capability mixed matrix membranes for CO2 separation, it is vital to construct the suitable transport channels to enhance the diffusivity-enabled selectivity as well as an excellent affinity toward target gas molecules to increase the solubility-based selectivity. Herein, composite membranes were constructed by integrating two-dimensional MXene nanosheets into a carboxylated nanocellulose matrix. The carboxyl-rich cellulose interacts with the surface groups of MXene, which contributes to a superior interface compatibility and repairs the non-selective voids. In particular, one-dimensional nanocellulose can intercalate into MXene laminates to regulate the interlayer spacing and suppress the re-stacking of MXenes. The resulting MC-3 membrane (with a MXene loading of 15.4 wt%) possesses the optimal separation performance, bearing a CO2 permeability of 156.7 Barrer with ideal selectivities of 47.8 for CO2/CH4 and 42.6 for CO2/N2. For the mixed gas separation, the MC-3 membrane exhibits separation factors of 48.5 and 55.3 for CO2/N2 and CO2/CH4, respectively. This excellent separation performance is resulted from the enhanced interfacial property, suitable MXene channel size and good CO2-solubility of nanocellulose.