Imine-linked polymer derived N-Doped microporous carbons in PEO-based mixed matrix membranes for enhanced CO2/N2 separation: A comparative study

Abstract

Imine-linked porous organic polymers (POPs) have attracted much attention in gas separation due to their high porosity and adjustable structure, and they are great potential candidates for nitrogen-doped porous carbons for CO2/N2 separation in mixed matrix membranes (MMMs). In this work, we synthesized imine-linked POPs via a facile method and obtained their derived carbons N-CSs via carbonization under an inert atmosphere. We found that the textural structure and functional surface of N-CSs are well inherited and further developed due to the high thermal stability of N-POPs. Nitrogen-containing functional groups in N-POPs and N-CSs improved the interfacial compatibility between polymer and fillers via hydrogen bonds. The textural structure of N-CSs with abundant narrower ultra-micropores (0.53 nm), as well as high nitrogen functional groups (4.65 wt%), endows poly (ethylene oxide) (PEO) membranes with superior molecular sieving ability for CO2 over N2 and fast CO2 transport channels. For instance, MMMs with 2.0 wt% loading of N-CSs exhibit an admirable gas separation performance with CO2 permeability of 540.4 Barrer and CO2/N2 selectivity of 61.3, surpassing the Upper bound (2019). The long-term stability of both MMMs is explored, which shows great potential in practical CO2 capture applications. This strategy of carbonization of imine-linked porous polymers provides ideas for the preparation of high-performance porous carbon-based MMMs and carbon molecular sieve membranes (CMSMs).