Facilitating CO₂ Transport Across Mixed Matrix Membranes Containing Multifunctional Nanocapsules

Mixed matrix membranes (MMMs) have exhibited advantages in overcoming the trade-off effect, although it is still intensively demanded in the design of multifunctional fillers to improve CO₂ separation performance. At present, MMMs with transport channels present an effective strategy to obtain ultrahigh CO₂ permselectivity. In this work, Pebax-based MMMs was fabricated by incorporating nanocapsules (NCs), whose exterior, interior and transverse shell surfaces contained abundant carboxylic acid groups. NCs, similar to vesicles in cells, provide favorable physical and chemical microenvironments to the constructed CO₂ transport channels, enhancing the CO₂ permselectivity via both a facilitated transport mechanism and a solution-diffusion mechanism. CO₂ permselectivity of MMMs doped with 20 wt % NCs surpassed the 2008 Robeson limit; an increase in CO₂ permeability was up to 1431 ± 35 Barrer for pure gas, which was a 362% enhancement from the pure membrane, and an increase of the CO₂/CH₄ and CO₂/N₂ ideal selectivities to 46 ± 1.4 and 69 ± 2.7, corresponding to 44% and 23% enhancements from the pure membrane, respectively. This study provides an ingenious strategy to enhance the gas permselectivity of MMMs.