Enhanced Membrane Performance for Gas Separation by Coupling Effect of the Porous Aromatic Framework (PAF) Incorporation and Photo-Oxidation

Abstract

Membrane separation is a promising technology for hydrogen purification or carbon capture due to its high energy efficiency. However, the trade-off between permeability versus selectivity and the gradual reduction of membrane permeability caused by physical aging restrict further development of glassy membranes. Poly(1-trimethylsilyl-1-propyne) (PTMSP), a highly permeable polymer, is limited by its low selectivity and fast physical aging properties. Mixed matrix membranes (MMMs) have been considered as an effective approach to improve membrane performance by embedding nanoparticles into a polymer matrix. By expanding our previous studies on PTMSP MMMs, which illustrated the effects of the incorporated nanoparticle size, their dispersion behavior, and interaction at the polymer–nanoparticle interface on the overall membrane performance, this study further investigated the coupling effects of porous aromatic framework (PAF-1) incorporation and the subsequent post-UV treatment on PTMSP/PAF-1 MMMs. The resulting membrane had enhanced gas permeability (up to 76% increase) contributed by highly porous PAF-1 incorporation and simultaneously improved gas selectivity (up to 260% increase) granted by the densified/selective thin layer formed on the membrane surface upon UV irradiation. This optimum membrane performance surpassed the 2008 upper bound [Robeson, L. M. The upper bound revisited. Journal of Membrane Science 2008, 320 (1), 390–400] for CO2 gas pairs (CO2/CH4 and CO2/N2) and reached the 2015 upper bound [Comesaña-Gándara, B.; Chen, J.; Bezzu, C. G.; Carta, M.; Rose, I.; Ferrari, M.-C.; Esposito, E.; Fuoco, A.; Jansen, J. C.; McKeown, N. B. Redefining the Robeson upper bounds for CO2/CH4 and CO2/N2 separations using a series of ultrapermeable benzotriptycene-based polymers of intrinsic microporosity. Energy & Environmental Science 2019, 12 (9), 2733–2740] for H2/CH4 separation. Furthermore, UV-treated membranes also showed a slower physical aging rate than the corresponding non-UV treated samples.