Mixed-matrix membranes consisting of Pebax and novel nitrogen-doped porous carbons for CO2 separation

Abstract

Fabricating high-performance mixed matrix membranes (MMMs) for CO 2 separation is of great importance for industrial application, but the poor compatibility between polymer and filler hinders their further development. Herein, novel nitrogen-doped porous carbons (NPC) were gained by a facile hydrothermal reaction between glucose and melamine, subsequently KOH activation. Highly micropore NPC with the BET surface area of 1229.36 m 2 g −1 and Langmuir surface area of 1868.46 m 2 g −1 accompanied with the BJH pore volume of 0.68 cm 3 g −1 was achieved by scanning electron microscopy (SEM) and N 2 adsorption. After blending with polyether-block-amide (Pebax), the as-obtained MMMs showed excellent mechanical properties probably due to the homogeneous dispersion of NPC in the Pebax as shown in SEM results. The nitrogen in MMMs was expected to be significantly increased upon incorporation with NPC, as verified by attenuated total reflectance Fourier-transform infrared spectroscopy, thus increased the CO 2 transport. MMM with 5 wt% NPC exhibited a CO 2 permeability of 553 Barrer. This value is much higher than that of the pristine Pebax membrane. Surprisingly, a significantly improved CO 2 /N 2 selectivity of as high as 56.4 was observed for MMMs. Thus, MMM having a 5 wt% NPC had an excellent gas separation, approaching Robeson's upper bound revised in 2019, which was superior to the one incorporated with other activated carbons prepared from similar reactants. The enhanced separation performance is mainly ascribed to the presence of nitrogen-containing groups for high CO 2 affinity and also the micropore structure to promote CO 2 diffusion in NPC. These results indicated that the improvement in gas permeability and ideal selectivity simultaneously could be achieved by MMMs using the microporous and functional nanofillers. • Novel nitrogen-doped porous carbons were introduced to Pebax to prepare MMMs for high performance CO 2 separation. • The nitrogen in porous carbons can provide more affinity sites for CO 2 transport. • Thus, a CO 2 permeability of as high as 553 Barrer with a CO 2 /N 2 selectivity of 56.4 was observed.