Polyethyleneimine-modified multi-walled carbon nanotubes mixed matrix membranes for CO2/N2 separation

In recent years, membrane separation technology has received extensive attention in CO2/N2 separation. Carbon nanotubes (CNTs) were regarded as ideal fillers for constructing high permeability mixed matrix membranes (MMMs) due to their special tubular structure. However, the interfacial compatibility between CNTs and organic polymer phases is a large challenge, seriously hindering the development of carbon-based mixed matrix membranes. In this work, we proposed a novel polyethyleneimine (PEI) surface functionalization strategy to effectively improve the compatibility between multi-walled carbon nanotubes (MWCNTs) and Pebax-1657. The as-prepared PEI@MWCNTs/Pebax-1657 MMMs were analyzed by XRD, EDS, FTIR, TG, etc. The PEI can improve the compatibility of MWCNTs with the polymer matrix. In addition, the abundant amino groups in the PEI structure can provide ample active sites for CO2, which can improve CO2 permeability and CO2/N2 selectivity simultaneously. Combining the low resistance of MWCNTs to gas transport, the membrane showed 178.08% enhancement in selectivity (82.06) of CO2/N2 compared to the pristine membrane with 152.49% increment in the permeability (150.51 Barrer) of CO2. This work provides a novel strategy for preparing carbon-based mixed matrix membranes with high gas separation performance. [Display omitted] •Polyethyleneimine-modified multi-walled carbon nanotubes were prepared to construct PEI@MWCNTs/Pebax-1657 MMMs.•MMMs showed 178.08% enhancement in CO2/N2 selectivity and 152.49 % increasement in CO2 permeability.•MMMs showed the enhanced CO2/N2 selectivity of 82.06 and CO2 permeability of 150.51 Barrer.•This work provides a new strategy for fabricating CO2/N2 separation membranes to surpass the Robeson upper bound.