Enhanced CO2/CH4 separation performance of mixed-matrix membranes through dispersion of sorption-selective MOF nanocrystals

• Published in: Journal of membrane science 2018-10, Vol.563, p.360-370
• Main Authors: Chen, Ke, Xu, Kai, Xiang, Long, Dong, Xiao, Han, Yue, Wang, Chongqing, Sun, Lin-Bing, Pan, Yichang
• Format: Article
• Language: English
• Subjects: CO2 capture; Gas separation; KAUST-7; Metal-organic frameworks; Mixed-matrix membrane
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2018.06.007

Mixed matrix membranes (MMMs) derived from metal-organic frameworks (MOFs) nanocrystals represent a promising alternative for overcoming the trade-off between permeability and selectivity derived from the pristine polymeric membrane. The selection of MOFs fillers are mainly focused on their diffusion-selectivity property for gas-pairs. However, the improvement of both gas-permeability and selectivity through addition of sorption-selective MOFs are rarely reported. Herein, the incorporation of CO2-philic KAUST-7 (also referred to as NbOFFIVE-1-Ni) nanocrystals makes the neat 6FDA-Durene polyimide membrane more permeable and more selective, surpassing the state-of-the-art 2008 Robeson upper bound for CO2/CH4. Nano-sized (~ 80 nm) KAUST-7 crystals with sharp particle size distribution were first fabricated through a co-solvent synthesis method. The explored gas transportation mechanism indicates that the improvement of CO2/CH4 selectivity on MMMs are attributed to the significant raise of the sorption-selectivity rather than the diffusion-selectivity. The favorable interfacial interaction between the imide groups of the 6FDA and the H of the pyrazine in the KAUST-7 enhances plasticization resistance of the neat polymer membrane. The developed MMMs exhibit a promising application in CO2 capture from natural- and bio-gas. [Display omitted] •KAUST-7 nanocrystals with uniform size distribution were first synthesized.•KAUST-7-based MMMs were first fabricated for effective separation of CO2/CH4.•The separation performance of MMMs surpasses the upper bound for CO2/CH4 mixture.•The MMMs exhibit improved plasticization-resistant property for CO2 purification.