Sorption-enhanced thin film composites with metal-organic polyhedral nanocages for CO2 separation

Abstract The atom transfer radical polymerization (ATRP)-based continuous assembly of polymers (CAP) is a promising approach for fabricating thin film composite (TFC) membranes for high flux. Here, we report the preparation of CO2-selective TFC mixed matrix membranes (MMMs) by incorporating different amounts of [Cu24(m-bdc)24(EG)3(DMF)12] (EG3-MOP) nanocages (e.g., 2.5, 5, and 10 wt%) as CO2-philic fillers in a poly(poly(ethylene glycol) dimethacrylate glycol) dimethacrylate (PEG9DMA) matrix via the ATRP-based CAP technique. The EG3-MOP nanocages are homogenously distributed in the PEG9DMA matrix with a good compatibility between them at up to 5 wt% of EG3-MOP nanocages due to the hydrophilic interactions between the triethylene oxide tails of EG3-MOP and the PEG of the PEG9DMA matrix. Additionally, both CO2 permeance and CO2/N2 selectivity increased with increasing contents of EG3-MOP nanocages up to 5 wt% via a gradual increase in CO2 solubility because of the favorable interaction of both unsaturated Cu(II) sites and triethylene oxide in EG3-MOP with CO2. In particular, the EG3-MOP/PEG9DMA (5/95 wt/wt) TFC-MMM enhanced both CO2 permeance and CO2/N2 permselectivity relative to those of the pristine PEG9DMA membrane by 45 and 50%, respectively, attaining a CO2 permeance of 448 GPU and a CO2/N2 selectivity of 30. In addition, it exhibited a good CO2/N2 separation performance under equimolar mixed gas conditions at 35 °C, further supporting that our TFC-MMMs fabricated via the ATRP-based CAP technique are attractive for CO2 separation.