Tuning microcavities in thermally rearranged polymer membranes for CO2 capture

Abstract

Microporous materials have a great importance in catalysis, delivery, storage and separation in terms of their performance and efficiency. Most microporous materials are comprised of inorganic frameworks, while thermally rearranged (TR) polymers are a microporous organic polymer which is tuned to optimize the cavity sizes and distribution for difficult separation applications. The sub-nano sized microcavities are controlled by in situ thermal treatment conditions which have been investigated by positron annihilation lifetime spectroscopy (PALS). The size and relative number of cavities increased from room temperature to 230 °C resulting in improvements in both permeabilities and selectivities for H(2)/CO(2) separation due to the significant increase of gas diffusion and decrease of CO(2) solubility. The highest performance of the well-tuned TR-polymer membrane was 206 Barrer for H(2) permeability and 6.2 of H(2)/CO(2) selectivity, exceeding the polymeric upper bound for gas separation membranes.

Effect of polymer structure on gas transport properties of selected aromatic polyimides, polyamides and TR polymers

“…Similar results were reported by Park et al 2 and Han et al 21 for APAF-6FDA-SS and APAF-6FCl, respectively. Despite APAF-6FDA and APAF-6FCl TR polymers having nearly identical structures, these polymers showed differences in transport properties for all gases considered.…”

“…2,4,21,65,[67][68][69] To investigate the role of thermal rearrangement on transport properties for our samples, we first discuss our results in comparison with other studies in the literature and then compare permeability and selectivity of our precursor and TR polymer samples using free volume theory.…”

“…21 In this study, near-quantitative thermal rearrangement can be achieved at temperatures 100°C lower for a polyamide-based sample than for a polyimide of similar backbone structure. Theoretical mass loss was calculated as the mass loss expected for stoichiometric conversion of the polyimide or polyamide precursors to polybenzoxazoles (cf., Table 2).…”

Electrochemical performance of a thermally rearranged polybenzoxazole nanocomposite membrane as a separator for lithium-ion batteries at elevated temperature

“…At a higher C-rate (1.0 C), however, the discharge capacities of TR-PBO 4, TR-PBO 1, and Celgard 2400 based cells were 103 mAh g À1 , 78 mAh g À1 , and 56 mAh g À1 , respectively. Two different TR-PBO based cells exhibited higher capacities than the Celgard 2400 based cell due to their excellent wettability, which can improve the Li-ion mobility [19]. As shown in Fig.…”

Recent developments in membranes for efficient hydrogen purification

“…To date, only a handful of high-performance membranes based on TR polymers have been reported for H 2 /CO 2 separation. Han et al suggested that polymer precursors with more rigid main chain structures should be chosen and thermal rearrangement should occur at a lower temperature so as to obtain smaller cavity size that is suitable for H 2 /CO 2 separation[156]. Following this strategy, TR-polybenzoxazole (TR-PBO) membranes were prepared from three representative rigid poly(hydroxylamide)s (PAHs) including meta-phenylene, para-phenylene and hexafluoroisopropylidene bisphenylene moieties as precursors, to investigate the effects of precursor structures on physicochemical properties as well as gas separation performances of the resultant membranes.…”