It is imperative to research CO 2 separation membrane in terms of the issues of greenhouse gas emission. In this work, zeolitic imidazolate frameworks-8 (ZIF-8) particles in situ inserted by multiwalled carbon tubes (MWCNTs) (MWCNTs@ZIF-8) were embedded into Pebax matrix to fabricate mixed matrix membranes (MMMs). The incorporated ZIF-8 particles increased the free volume of membranes, resulting in the improvement of the CO 2 permeability. The functionalized MWCNTs in situ inserted into ZIF-8 particles not only avoided the aggregation of ZIF-8 particles but also enhanced the CO 2 adsorption property, resulting in the improvement of the CO 2 /N 2 selectivity. Furthermore, the MWCNTs can provide rapid transport channels for CO 2 molecules between two adjacent ZIF-8 particles and high mechanical properties for membranes. As a result, the MMMs with 8 wt% MWCNTs@ZIF-8 exhibited an excellent separation performance with CO 2 permeability of 186.3 Barrer and CO 2 /N 2 selectivity of 61.3, which surpassed the 2008 Robeson upper-bound. This study provided a new strategy for preparing high-performance CO 2 separation membranes.
Jian Guan,Xiangzeng Wang,Jingcheng Du,Quansheng Liang,Wen He,Ying Liu,Ji Ma,Chunwei Zhang,Jiangtao Liu
Polymers of intrinsic microporosity (PIMs) are promising candidates for carbon dioxide (CO 2 ) separation and capture from flue gas or natural gas. PIM-1, which has excellent gas permeation properties over the Robeson upper bound (1991), has been widely functionalized to further enhance the CO 2 permeability or selectivity. In this work, a simple and readily processive surface modification method has been proposed via hydrolysis of the PIM-1 membrane. The two hydrolysis processes by the acid method, amidation and carboxylation processes, have been conducted to functionalize the surface of PIM-1 membranes forming N A -PIM-1 and C A -PIM-1 membranes. The TGA, FT-IR spectra and NMR results verify that the composition and structure inside the PIM-1 membrane remain unchanged. XPS and NMR spectra demonstrate that the nitrile group at the surface was successfully functionalized with an amine group or carboxyl group. The CO 2 permeability and CO 2 /N 2 selectivity of the N A -PIM-1 membrane both increased to 4593.2 Barrer and 28.5, respectively. Another advantage of N A -PIM-1 membranes is the coordination site from introduced nitrogen atoms with zinc ions to form N A -PIM-1-Zn, which could further react with PEI to introduce amine-rich groups on the surface of the PIM-1 membrane. The CO 2 /N 2 selectivity of the N A -PIM-1-Zn-PEI membrane coated with PEI on the surface increases 45.4% compared to the unmodified PIM-1 membranes, with CO 2 permeability decreasing only 15.5% compared to the unmodified PIM-1 membrane. The N A -PIM-1 and N A -PIM-1-Zn-PEI membranes both surpass the Robeson upper bound (2008) even under mixed gas feeding, suggesting that surface modification of PIM-1 is a promising approach for CO 2 capture from natural gas and flue gas.
Shuang Wang,Dudu Li,Zelong Xu,Fan Zhou,Zhihua Qiao,Zibo Yang,Zhi Wang
Coordination polymer (CP) glasses offer high processability and permanent accessible pores, having promising potential in gas separation. However, their low porosity makes it difficult to prepare high-performance gas separation membranes. In this work, we combined the advantages of CP glasses and inorganic fillers, and selected ag Zn-P-dmbIm as the continuous phase and hydroxylated multi-walled carbon nanotubes (HMWCNTs) as the dispersed phase to prepare HMWCNTs/ ag Zn-P-dmbIm mixed matrix membranes (MMMs). The very favorable interfacial compatibility and excellent CO 2 /N 2 gas separation performance of the MMM-2 membrane were demonstrated by a series of characterizations. The test results revealed that the CO 2 permeability and ideal CO 2 /N 2 selectivity of MMM-2 membrane were 9776.8 Barrer and 31.1, respectively, which exceeded the Robeson 2019 upper bound. In addition, the well-defined long-term stability of the MMM-2 membrane lays the foundation for realizing gas separation membranes for industrial applications in practice. This provides a strategy for the subsequent preparation of CP glasses-based MMMs.
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