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CO 2 -CH 4 mixed-gas sorption and permeation properties of a ladder polymer (PIM-Trip-TB) were measured experimentally at 35 °C to interpret nonideal transport behavior of polymers of intrinsic microporosity (PIMs). Both CH 4 and CO 2 mixed-gas solubilities were lower than those in the pure-gas environment mainly due to competitive sorption. In the range of pressures tested, the CO 2 /CH 4 mixed-gas solubility selectivity of PIM-Trip-TB coincided on average with the value at infinite dilution, and at all pressures, it was higher than the pure-gas solubility selectivity. Because CO 2 diffusion coefficient was found insensitive to mixture effects, we inferred that the increased diffusion coefficient of CH 4 and the consequent loss of CO 2 /CH 4 permselectivity in mixture environment were correlated to CO 2 -induced alteration of the selective diffusion domains of PIM-Trip-TB. Similar effects were also found for PIM-1 by an analysis of pure- and mixed-gas experimental permeation and sorption data. The increase of CH 4 mixed-gas diffusion coefficients from the pure-gas values was more pronounced for both PIMs (PIM-Trip-TB and PIM-1) than for a conventional low-free volume polymer 6FDA-mPDA polyimide reported previously; this indicates that the high intrachain rigidity in PIMs cannot restrain unfavorable mixture effects on CO 2 /CH 4 diffusion and permeability selectivity. Image 1 • CO 2 -CH 4 mixed-gas solubility in PIM-Trip-TB deviates from pure-gas values. • CO 2 vs. CH 4 mixed-gas solubilities can be fitted linearly regardless of concentration. • Equimolar CO 2 /CH 4 solubility selectivity in mixture is higher than pure-gas one. • CO 2 alters polymer size sieving domains thus depressing mixed-gas permselectivity. • Intrachain rigidity does not limit CO 2 -induced plasticization during CO 2 -CH 4 separations. [ABSTRACT FROM AUTHOR]

An intrinsically microporous polyimide is synthesized in m-cresol by a one-pot high-temperature condensation reaction of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and newly designed 2,6 (7)-dihydroxy-3,7(6)-diaminotriptycene (DAT1-OH). The 6FDA-DAT1-OH polyimide is thermally stable up to 440 °C, shows excellent solubility in polar solvents, and has moderately high Brunauer-Teller-Emmett (BET) surface area of 160 m2 g−1, as determined by nitrogen adsorption at −196 °C. Hydroxyl functionalization applied to the rigid 3D triptycene-based diamine building block results in a polyimide that exhibits moderate pure-gas CO2 permeability of 70 Barrer combined with high CO2/CH4 selectivity of 50. Mixed-gas permeation studies demonstrate excellent plasticization resistance of 6FDA-DAT1-OH with impressive performance as potential membrane material for natural gas sweetening with a CO2 permeability of 50 Barrer and CO2/CH4 selectivity of 40 at a typical natural gas well partial pressure of 10 atm. [ABSTRACT FROM AUTHOR]

Hydrogen is an emerging energy source with a wide range of applications in transportation, electricity generation, and manufacturing of important chemicals such as ammonia and methanol. Hydrogen is commonly coproduced with CO 2 using steam reforming of methane and its purification is typically achieved using energy-intensive processes such as pressure swing adsorption (PSA) and cryogenic distillation. Membrane technology with potentially lower energy consumption and lower carbon footprint could play an important role in developing a more sustainable hydrogen economy. In this study, we prepared carbon molecular sieve (CMS) membranes by the pyrolysis of a highly aromatic catalytic arene-norbornene annulation (CANAL)-Tröger's base ladder polymer of intrinsic microporosity precursor — CANAL-TB-1. CMS membranes obtained by pyrolysis between 600 and 900 °C displayed excellent gas separation performance for hydrogen/carbon dioxide separation and related applications. The CANAL-CMS-800 °C membrane showed a pure-gas hydrogen permeability of 41 Barrer with H 2 /CO 2 , H 2 /N 2 , and H 2 /CH 4 selectivity values of 39, 1952, and >8200 at 35 °C. Increasing the pyrolysis temperature to 850 and 900 °C further boosted the selectivity. For example, the CANAL-CMS-900 °C exhibited a stable long-term mixed-gas performance over a period of 38 days with an unprecedented H 2 /CO 2 selectivity of 174 and H 2 permeability of 8.2 Barrer at 10 bar total feed pressure and 100 °C, which significantly exceeded the performance of previously reported polymers and related CMS membrane materials. [Display omitted] • A microporous ladder polymer CANAL-TB-1 was employed as a precursor for CMS membranes fabrication. • CMS membranes pyrolized at high temperatures showed excellent H 2 /CO 2 gas separation performance. • CMS membranes pyrolyzed at 900 °C exhibited pure-gas H 2 /CO 2 selectivity of 248. • CMS membranes showed stable long-term mixed-gas H 2 /CO 2 selectivity of 174 at 10 bar and 100 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ladder PIMs define state-of-the-art polymeric membrane materals for air separation, hydrogen recovery and CO 2 removal applications. • Hydroxyl-functionalized and carboxyl-functionalized ladder PIMs and PIM-PIs. • Physical aging and penetrant-induced plasticization need to be minimized for industrial membrane applications. • PIMs are a new class of precursor materials for ultra-selective carbon molecular sieves. • Polymer scale-up and thin-film membrane formation development are required for commercial utilization. Solution-processible polymers of intrinsic microporosity (PIMs) are appealing materials for membrane applications due to their chemical and structural variety available from a wide range of PIM building blocks and significantly improved gas separation performance compared to conventional low-free-volume glassy polymers. This review highlights recent materials design developments in PIMs including: (i) benzotriptycence-based ladder PIMs, (ii) norbornyl-benzocyclobutene-based PIMs made by catalytic arene-norbornene annulation (CANAL), (iii) high-performance functionalized PIMs (iv) PIM-based thin-film composite membranes, and (v) PIM-based carbon molecular sieve (CMS) membranes. Significant advances in gas separation properties of new generation PIMs have set the recent 2015 H 2 /N 2 , H 2 /CH 4 , and O 2 /N 2 upper bounds, 2018 CO 2 /CH 4 mixed-gas upper bound, and 2019 pure-gas CO 2 /N 2 and CO 2 /CH 4 pure-gas upper bounds. Realizing the full potential of PIMs for future commercial use requires further improvements in (i) gas-pair selectivity, especially for challenging separations, (ii) stability against physical aging and plasticization, (iii) polymer scale-up, and (iv) reproducible membrane fabrication. [ABSTRACT FROM AUTHOR]

A triptycene-based diamine, 1,3,6,8-tetramethyl-2,7-diamino-triptycene (TMDAT), was used for the synthesis of a novel solution-processable polyamide obtained via polycondensation reaction with 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) (6FBBA). Molecular simulations confirmed that the tetrasubstitution with ortho-methyl groups in the triptycene building block reduced rotations around the C–N bond of the amide group leading to enhanced fractional free volume. Based on N2 sorption at 77 K, 6FBBA-TMDAT revealed microporosity with a Brunauer–Emmett–Teller (BET) surface area of 396 m2 g−1; to date, this is the highest value reported for a linear polyamide. The aged 6FBBA-TMDAT sample showed moderate pure-gas permeabilities (e.g., 198 barrer for H2, ~109 for CO2, and ~25 for O2) and permselectivities (e.g., αH2/CH4 of ~50) that position this polyamide close to the 2008 H2/CH4 and H2/N2 upper bounds. CO2–CH4 mixed-gas permeability experiments at 35 °C demonstrated poor plasticization resistance; mixed-gas permselectivity negatively deviated from the pure-gas values likely, due to the enhancement of CH4 diffusion induced by mixing effects. [ABSTRACT FROM AUTHOR]

Back Cover: Triptycene is a unique building block for high‐performance polymers due to its symmetric D3h structure containing fixed internal free‐volume elements. A novel triptycene diamine (2,6(7)‐dihydroxy‐3,7(6)‐diaminotriptycene) (DAT1‐OH) for the synthesis of an intrinsically microporous polyimide (6FDA‐DAT1‐OH) is described by Ingo Pinnau and co‐workers in article number 1700303. As illustrated in the cover design, it exhibits excellent performance as membrane material for gas separation applications, specifically for the removal of CO2 from natural gas. [ABSTRACT FROM AUTHOR]

An intrinsically microporous hydroxyl-functionalized polyimide (PIM-PI) made from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 2,6(7)-dihydroxy-3,7(6)-diaminotriptycene (DAT1-OH), was thermally converted to polybenzoxazole (PBO). The thermal rearrangement of the PIM-PI to PBO significantly increased the free volume, which was reflected by a boost in its microporosity as indicated by enhanced Brunauer-Emmett-Teller (BET) surface area from 167 to 405 m2 g−1. The increase in free volume noticeably improved the gas permeability but also resulted in reduced gas-pair selectivity. The fresh PBO membrane made by thermal treatment at 460 °C for 30 min (TRIP-TR-460-30) with a PBO conversion of 98% displayed a 20-fold higher CO 2 permeability of 840 barrer than the initial value of 43 barrer for the 6FDA-DAT1-OH polyimide at the expense of ~ 60% decrease in pure-gas CO 2 /CH 4 selectivity from 52 to 21. The TRIP-TR-460-30 PBO showed good performance for propylene/propane separation with pure-gas C 3 H 6 permeability of 21 barrer and C 3 H 6 /C 3 H 8 selectivity of 16 for a 28-days aged sample. When tested under mixed-gas conditions C 3 H 6 permeability dropped to 12.8 barrer and C 3 H 6 /C 3 H 8 selectivity of 8. TRIP-TR-460-30 PBO displayed mechanical properties comparable some rigid polyimides with tensile strength, Young's modulus and elongation at break of 58 MPa, 1.83 GPa and 4.3%, respectively. Image 1 • TR-derived PBO membranes made from 6FDA/triptycene OH-based diamine polyimide. • Fully converted PBO exhibited improved gas permeability but reduced selectivity. • Physical aging had large effect on gas permeability but small effect on selectivity. • PBO demonstrated performance located on the propylene/propane upper bound. [ABSTRACT FROM AUTHOR]