Abstract
Mixed matrix membranes (MMMs) have attracted significant attention for overcoming the limitations of traditional polymeric membranes for gas separation through the improvement of both permeability and selectivity. However, the development of defect-free MMMs remains challenging due to the poor compatibility of the metal–organic framework (MOF) with the polymer matrix. Thus, we report a surface-modification strategy for a MOF through grafting of a polymer with intrinsic microporosity onto the surface of UiO-66-NH2. This method allows us to engineer the MOF–polymer interface in the MMMs using Pebax as a support. The insertion of a PIM structure onto the surface of UiO-66-NH2 provides additional molecular transport channels and enhances the CO2 transport by increasing the compatibility between the polymer and fillers for efficient gas separation. As a result, MMM with 1 wt% loading of PIM-grafted-MOF (PIM-g-MOF) exhibited very promising separation performance, with CO2 permeability of 247 Barrer and CO2/N2 selectivity of 56.1, which lies on the 2008 Robeson upper bound. Moreover, this MMM has excellent anti-aging properties for up to 240 days and improved mechanical properties (yield stress of 16.08 MPa, Young’s modulus of 1.61 GPa, and 596.5% elongation at break).
Highlights
Greenhouse gas production is increasingly posing a serious environmental threat, and, as a result, CO2 separation technologies have attracted significant attention as a potential way to mitigate rising CO2 levels in the atmosphere [1–4]
This study has provided an effective strategy to prepare matrix membranes (MMMs) by embedding PIMg-metal–organic framework (MOF) into a Pebax polymer matrix
This contributed to improvements in CO2 permeability by 75% and CO2 /N2 selectivity by 59% of the PIM-g-MOF-1 MMM compared to the pristine Pebax membrane
Summary
Greenhouse gas production is increasingly posing a serious environmental threat, and, as a result, CO2 separation technologies have attracted significant attention as a potential way to mitigate rising CO2 levels in the atmosphere [1–4]. Among the various CO2 separation techniques, membrane separation stands out for its low energy consumption, environmental friendliness, simple operation, ease of maintenance, and good performance [4–7]. The organic polymer membranes with the best gas separation performance are considered to be those with high CO2 permeability combined with high CO2 selectivity. There is a general trade-off relationship between the permeability P (the product of diffusivity and solubility, P = D × S) and selectivity α (the permeability ratio between two gases, PA /PB ). More permeable polymers are generally less selective, which is defined by the Robeson upper bound [10,11]
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