Covalent organic frameworks (COFs) show exceptional promise for CO2-selective mixed matrix membranes (MMMs) due to their tunable porosity and structural robustness. To mitigate COF aggregation in MMMs, we present an in situ growth strategy by directly integrating COF precursors into a polymer matrix. By optimizing reaction conditions, we achieve uniform dispersion and successful in situ formation of TpPa (derived from 1,3,5-triformylphloroglucinol and p-phenylenediamine) within the Pebax matrix. The optimized membrane exhibits a high CO2 permeability of 313.4 Barrer (45.8% higher than pure Pebax) and CO2/N2 selectivity of 22.6, along with long-term stability. Positron annihilation lifetime spectroscopy further reveals how the integration of COFs modulates the membrane’s free-volume properties. This study not only addresses filler dispersion challenges but also provides a viable approach for fabricating high-performance, stable CO2 separation membranes.
Haiyang Zhang,Ruili Guo,Jinpeng Hou,Zhong Wei,Xueqin Li
In this study, a carbon nanotubes composite coated with N-isopropylacrylamide hydrogel (NIPAM-CNTs) was synthesized. Mixed-matrix membranes (MMMs) were fabricated by incorporating NIPAM-CNTs composite filler into poly(ether-block-amide) (Pebax MH 1657) matrix for efficient CO2 separation. The as-prepared NIPAM-CNTs composite filler mainly plays two roles: (i) The extraordinary smooth one-dimensional nanochannels of CNTs act as the highways to accelerate CO2 transport through membranes, increasing CO2 permeability; (ii) The NIPAM hydrogel layer coated on the outer walls of CNTs acts as the super water absorbent to increase water content of membranes, appealing both CO2 permeability and CO2/gas selectivity. MMM containing 5 wt % NIPAM-CNTs exhibited the highest CO2 permeability of 567 barrer, CO2/CH4 selectivity of 35, and CO2/N2 selectivity of 70, transcending 2008 Robeson upper bound line. The improved CO2 separation performance of MMMs is mainly attributed to the construction of the efficient CO2 transport pathways by NIPAM-CNTs. Thus, MMMs incorporated with NIPAM-CNTs composite filler can be used as an excellent membrane material for efficient CO2 separation.
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