Effects on Carbon Molecular Sieve Membrane Properties for a Precursor Polyimide with Simultaneous Flatness and Contortion in the Repeat Unit

Abstract

Carbon molecular sieve (CMS)-based membrane separation is a promising solution for hydrogen separation due to its great advantages on perm-selectivity, thermal stability, and chemical stability. To prepare high-performance CMS membranes, the molecular structure of polymer precursors and their arrangements should be primarily considered. In this work, a benzimidazole-based 6FDA (2,2'-bis(3,4'-dicarboxyphenyl) hexafluoropropane dianhydride)-type polyimide (PABZ-6FDA-PI) is chosen as precursor to prepare the CMS membrane. Effects of chain flatness and contortion in the polyimide precursor on gas-separation performance of CMS membranes were studied in detail by gas adsorption and permeation experiment. The H 2 permeability of CMS is up to 9500 Barrer and ideal selectivity of gas pairs of H 2 /CH 4 and H 2 /CO 2 is up to 3800 and 13, respectively. The comprehensive performance of hydrogen separation including H 2 /CO 2 , H 2 /N 2 , and H 2 /CH 4 gas pairs is located well above previously reported upper bounds for polymers.

Electron-mediated control of nanoporosity for targeted molecular separation in carbon membranes

“…When the pyrolysis temperature was raised to 800 °C, the selectivity was improved to 9 while the C 2 H 4 permeability dropped an order of magnitude. As another challenging example, H 2 /CO 2 ( ) selectivity of less than 10 is usually reported in CMS membranes regardless of the final pyrolysis temperature or the types of precursors 16 – 18 . In addition to the strong adsorption between CO 2 and carbon surfaces, which enhances intrinsic CO 2 permeability, the incomplete development of sub-0.5 nm ultramicropores in the CMS matrix suppresses the effective discrimination between H 2 and CO 2 .…”

Thermally Cross-Linked Amidoxime-Functionalized Polymers of Intrinsic Microporosity Membranes for Highly Selective Hydrogen Separation

“…Figure presents the H 2 separation performance of the TX-AOPIM-1 membranes in comparison with the Robeson upper bound and other reported data. ,− Notably, the TX-AOPIM-1 membranes realize the transformation from originally CO 2 /H 2 -selective to H 2 /CO 2 -selective. TX-AOPIM-1-390-48 exhibits a high H 2 /CO 2 selectivity up to 16.2, far exceeding the 2008 Robeson upper bound.…”

“…Ideal selectivity vs permeability of TX-AOPIM-1 membranes for (a) H 2 /CO 2 , (b) H 2 /CH 4 , and (c) H 2 /N 2 gas pairs. The data of the CMS (pyrolysis temperature between 550 and 650 °C), , polymer, − and thermally cross-linked PIM-1 membranes have been included for comparison.…”

“…53 To explore the aging behavior of TX-AOPIM-1 membranes, the variation of gas permeability and selectivity of TX-AOPIM-1-370-48 is monitored up to 180 days by three Ideal selectivity vs permeability of TX-AOPIM-1 membranes for (a) H 2 /CO 2 , (b) H 2 /CH 4 , and (c) H 2 /N 2 gas pairs. The data of the CMS (pyrolysis temperature between 550 and 650 °C), 48,49 polymer, 50−52 and thermally cross-linked PIM-1 28…”

Microporous Organic Polymers: A Synthetic Platform for Engineering Heterogeneous Carbocatalysts

“…[3] Conventionally, carbon allotropes, such as carbon nanotubes or graphene sheets, [4][5][6][7][8] and natural products, such as chitosan, lignin, or nutshell, [9][10][11] have been used for the formation of metal-free carbocatalysts via thermal processes, where the catalysts can then be functionalized with heteroatom precursors to achieve the desired catalytic performance. Similarly, synthetic polymers including poly(styrene)s, poly(vinylpyrrolidone)s, polyimides, and other polymer resins have been used to generate carbonaceous materials, [12][13][14][15] which can allow further intuitive and uniform structural manipulation of the carbocatalysts as facilitating the entire carbonization process.…”