PEO-based CO2-philic mixed matrix membranes compromising N-rich ultramicroporous polyaminals for superior CO2 capture

Abstract Polymer molecular sieve materials (PMS) are promising porous fillers that can be used to fabricate high-performance gas separation mixed matrix membranes (MMMs) to overcome the inherent trade-off. In this work, a nitrogen-rich ultramicroporous (0.34 nm, 0.50 nm) polyaminal network (PAN-NH2) was introduced into crosslinked PEO polymer to prepare CO2-philic MMMs with superior CO2 capture performance. Due to the synergistical interaction of the dipole-quadrupole and molecular sieving effect, PAN-NH2 demonstrates excellent molecular recognition of CO2. PAN-NH2 can be well dispersed in polymer matrix to achieve good polymer-filler interface compatibility. The incorporation of PAN-NH2 significantly improves the CO2 permeability and selectivity of membranes by increasing the CO2 solubility and providing a selective CO2 transport highway. For instance, the CO2 permeability of mixed gas (15% CO2/85% N2, 50% CO2/50% CH4) permeation tests for 2.0 wt% PAN-NH2/PEO was increased from 340 Barrer (crosslinked PEO) to 1160 Barrer along with CO2/N2 selectivity of 73.0 and CO2/CH4 selectivity of 19.7, surpassing the Upper bound (2019) and Upper bound (2008), respectively. The long-time stability of PAN-NH2/PEO MMMs is good, which endow them with great potential in practical CO2 capture. In addition, this work demonstrates the potential of functional ultramicroporous PMS in the preparation of high-performance MMMs for other gas separation processes.