Composite membranes were fabricated by incorporating carboxylic acid nanogels (CANs) into a Pebax MH 1657 matrix for potential applications in CO 2 /CH 4 (or N 2 ) separation. CANs were synthesized by precipitation polymerization of N-isopropylacrylamide (NIPAM), acrylic acid (AA) monomer and N,N′-methylenebisacrylamide (BIS) crosslinker. The incorporation of CANs simultaneously tailored favorable water environment and increased CO 2 transport sites within the membranes. With increasing CANs loading, the homogeneously dispersed CANs in the Pebax matrix offered more favorable water environment and the additional carboxyl group sites for efficient CO 2 transport, thus constructing interconnected preferential CO 2 transport passageways. The Pebax-CANs-30 composite membrane exhibited the highest gas separation performance, with the CO 2 /CH 4 and CO 2 /N 2 selectivities of 33 and 85 respectively, and a CO 2 permeability of 2026 Barrer (1 Barrer=10 −10 cm 3 (STP) cm/(cm 2 s cmHg), well surpassing the Robeson's upper bound limit reported in 2008. This effort will give rise to a new option to tailor water environment and increase CO 2 transport sites for fabricating high-performance CO 2 separation membranes .
Jin Du,Shuwei Liang,Meidi Wang,Yuhan Wang,Tianpei Yi,Zhiming Zhang,Fusheng Pan,Zhongyi Jiang
Facilitated transport membranes is a promising strategy to fabricate efficient separation membranes for aromatic/aliphatic mixtures. However, building up selective channels with uniformly distributed facilitated transport sites is still challenging. In this study, Cu-TAPB-COF (CuCOF) nanosheets , a kind of metal-covalent organic frameworks (MCOFs), were synthetized and introduced into poly (ether-block amide) (Pebax®2533) matrix to construct facilitated transport membranes for toluene/ n -heptane mixtures. As the aromatic skeleton linked by covalent interaction, CuCOF could provide continuous low mass transfer resistance channel. And Cu(I) exist in skeleton could serve as uniformly distributed facilitated transport sites and maintain a long-term stability. The resulting membrane exhibited a higher adsorption selectivity and lower swelling degree compared with pure Pebax membrane. The membrane exhibited high pervaporation separation performance for 50 wt% toluene/ n -heptane mixture. When the filling contents of CuCOF was 2.0 wt%, the membrane achieved a permeation flux of 937 g m −2 h −1 and the separation factor of 4.7.
Volatile organic compounds (VOCs) are pollutants detrimental to human health and the environment, necessitating the development of efficient separation technologies to support sustainable societal progress. Hybrid membranes incorporating metalated covalent organic frameworks (MCOFs) have shown great potential for VOCs separation due to the synergistic combination of polymer processability and the selective adsorption capacity of MCOFs. However, the performance of conventional MCOFs is limited by their microporous structures, which restrict molecular diffusion and accessibility to metal active sites. Herein, we have designed a mesoporous Cu(I)-metalated COF (Cu 3 L 3 -BD) with a pore diameter of 3.8 nm, which was further incorporated into poly(ether-block-amide) (Pebax) matrix to fabricate hybrid membranes (Pebax-Cu 3 L 3 -BD) for VOCs separation. The mesoporous channels facilitate improved gas transport and maximize exposure of Cu(I) coordination sites, thus enhancing the dissolution-diffusion process and improving the selectivity of Pebax-Cu 3 L 3 -BD. With a filler loading of 3 wt%, the Pebax-Cu 3 L 3 -BD exhibited optimal toluene permeance of 1.67 × 10 −6 mol μm m −2 s −1 Pa −1 and selectivity of 730, with the stability maintained over 120 h.
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