Improved CO2/N2 separation performance of Pebax composite membrane containing polyethyleneimine functionalized ZIF-8

Abstract Poor interfacial compatibility that often led to low gas separation performance is one of key challenges for developing composite membranes. In the present study, nanosized polyethyleneimine (PEI) functionalized ZIF-8 (PEI-ZIF-8) with good dispersion, having a particle size around 15 nm, has been synthesized via in-situ method and used as filler to fabricate Pebax/PEI-ZIF-8 composite membranes. Excluding the intrinsic porous structure and higher affinity with CO2 of PEI-ZIF-8 beneficial for CO2 selective transport, the large density of amine groups on PEI chains provide a good interfacial compatibility, and introduce facilitated CO2 transport path. Furthermore, PEI-ZIF-8 reduces the crystallinity of Pebax matrix, which is favorable for CO2 transport. The composite membrane with 5 wt% PEI-ZIF-8 shows a CO2 permeance of 13.0 GPU with a CO2/N2 selectivity of 49.0, which increases by 80.6% and 118.8% respectively in contrast with pristine Pebax membrane. The results demonstrate that nanoparticles functionalized by amine-polymer with long chains is effective for constructing composite membranes with good interfacial compatibility.