Bader Ghanem

Ultra-Microporous Triptycene-based Polyimide Membranes for High-Performance Gas Separation

This Communication describes the synthesis and exceptional gas transport properties of two robust, solution-processable ultra-microporous (<7 Å) PIM-polyimides – KAUST-PI-1 and KAUST-PI-2 – integrating a three-dimensional 9,10-diisopropyltriptycene contortion center into a rigid fused-ring dianhydride. Rotation about the imide bonds is restricted by ortho-substituted methyl groups in the diamine. Bridgehead substitution at the 9,10-positions compounds the benefi ts of triptycene on three fronts: [ 13 ] First, it offers tunability of the porous texture; second, the triptycene imparts rigidity to short bridgehead substituents, effectively enhancing the overall three-dimensionality and rigidity of the moiety; third, it bolsters solution-processability by enhancing solubility. Functionalizing the bridgeheads with short branched isopropyl chains [ 18 ] primes the microstructure for highly permeable and highly selective diffusion-dominated performance surpassing all known polymers in industrial gas separations [ 5 ] including hydrogen (H 2 /N 2 , H 2 /CH 4 ) and oxygen (O 2 /N 2 ) separations, which constitute ∼75% of the gas separation market. [ 19 ]

A nanoporous network polymer derived from hexaazatrinaphthylene with potential as an adsorbent and catalyst support

The synthesis and properties of a nanoporous network polymer incorporating 5,6,11,12,17,18-hexaazatrinapthylene (Hatn) as the rigid functional unit is described. This material is readily prepared from the efficient dibenzodioxane forming reaction between 2,3,8,9,14,15-hexachloro-5,6,11,12,17,18-hexaazatrinaphthylene and 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane and exhibits a high BET surface area (775 m2 g−1) similar to that obtained from related nanoporous networks based on phthalocyanine and porphyrin macrocycles. The ability of the Hatn unit to bind to metal ions was shown by the sequential binding of three palladium(II) dichloride moieties to a soluble model Hatn compound using a 1H NMR titration experiment. When exposed to an excess of palladium(II) dichloride in chloroform solution, the Hatn nanoporous network is shown to adsorb 3.9 mmol g−1 of the metal complex. The resulting material retains porosity (BET surface area = 347 m2 g−1) and should be useful as a heterogeneous catalyst. The Hatn network polymer is also shown to be effective for the adsorption of phenol from aqueous solution with a maximum adsorption of 5 mmol g−1, which is a significant improvement over the performance of activated carbon reported in similar studies.

Energy‐Efficient Hydrogen Separation by AB‐Type Ladder‐Polymer Molecular Sieves

Increases in hydrogen selectivity of more than 100% compared with the most selective ladder polymer of intrinsic microporosity (PIM) reported to date are achieved with self-polymerized A-B-type ladder monomers comprising rigid and three-dimensional 9,10-dialkyl-substituted triptycene moieties. The selectivities match those of materials commercially employed in hydrogen separation, but the gas permeabilities are 150-fold higher. This new polymer molecular sieve is also the most selective PIM for air separation.

Microporous polymeric materials

Abstract Microporous materials are solids that contain interconnected pores of molecular dimensions (i.e. 1 . There are two main classes of microporous materials widely used in industry: crystalline zeolites (aluminosilicates) and activated carbons. In the past decade, there has been an intense effort to optimize the porosity of these materials for various applications 2 , 3 . However, it is recognized that the design of entirely new microporous materials would open up exciting opportunities for fundamental research and industrial applications 3 .

How Do Organic Vapors Swell Ultrathin Films of Polymer of Intrinsic Microporosity PIM-1?

Dynamic sorption of ethanol and toluene vapor into ultrathin supported films of polymer of intrinsic microporosity PIM-1 down to a thickness of 6 nm are studied with a combination of in situ spectroscopic ellipsometry and in situ X-ray reflectivity. Both ethanol and toluene significantly swell the PIM-1 matrix and, at the same time, induce persistent structural relaxations of the frozen-in glassy PIM-1 morphology. For ethanol below 20 nm, three effects were identified. First, the swelling magnitude at high vapor pressures is reduced by about 30% as compared to that of thicker films. Second, at low penetrant activities (below 0.3p/p0), films below 20 nm are able to absorb slightly more penetrant as compared with thicker films despite a similar swelling magnitude. Third, for the ultrathin films, the onset of the dynamic penetrant-induced glass transition Pg has been found to shift to higher values, indicating higher resistance to plasticization. All of these effects are consistent with a view where immobilization of the superglassy PIM-1 at the substrate surface leads to an arrested, even more rigid, and plasticization-resistant, yet still very open, microporous structure. PIM-1 in contact with the larger and more condensable toluene shows very complex, heterogeneous swelling dynamics, and two distinct penetrant-induced relaxation phenomena, probably associated with the film outer surface and the bulk, are detected. Following the direction of the penetrants diffusion, the surface seems to plasticize earlier than the bulk, and the two relaxations remain well separated down to 6 nm film thickness, where they remarkably merge to form just a single relaxation.

A unique 3D ultramicroporous triptycene-based polyimide framework for efficient gas sorption applications

A novel 3D ultramicroporous triptycene-based polyimide framework with high surface area (1050 m2 g−1) and thermal stability was synthesized. It exhibits relatively high CO2 (3.4 mmol g−1 at 273 K and 1 bar), H2 (7 mmol g−1 at 77 K and 1 bar), and olefin sorption capacity, good CO2/N2 (45) and CO2/CH4 (9.6) selectivity at 273 K and 1 bar, as well as promising C2H4/CH4 and C3H6/CH4 selectivities at 298 K, making it a potential candidate for CO2 capture, H2 storage, and hydrocarbon gas separation applications.

New phenazine-containing ladder polymer of intrinsic microporosity from a spirobisindane-based AB-type monomer

A new solution-processable ladder polymer (PSBI-AB) of intrinsic microporosity with dibenzodioxane linkages and bis(phenazine) units was designed and synthesized by self-polymerization of an AB-type monomer containing both catechol and aromatic dichloride groups. Such polymerization is an effective way to synthesize high molecular weight polymers and has a significant advantage over AA-BB polycondensation due to the lack of the requirement for strict control over stoichiometric balance. This protocol can be used to prepare a variety of phenazine-containing ladder type PIMs from their aromatic tetramethoxy precursors. The obtained polymer had high average molecular mass, excellent thermal stability, a high BET surface area of 705 m2 g−1 and good solubility in some organic solvents such as chloroform, m-cresol and dichlorobenzene. Gas permeation measurements showed comparable results to the previously reported analogous PIM-7 for films made under the same formation protocol.

High-Pressure CO2 Sorption in Polymers of Intrinsic Microporosity under Ultrathin Film Confinement

Ultrathin microporous polymer films are pertinent to the development and further spread of nanotechnology with very promising potential applications in molecular separations, sensors, catalysis, or batteries. Here, we report high-pressure CO2 sorption in ultrathin films of several chemically different polymers of intrinsic microporosity (PIMs), including the prototypical PIM-1. Films with thicknesses down to 7 nm were studied using interference-enhanced in situ spectroscopic ellipsometry. It was found that all PIMs swell much more than non-microporous polystyrene and other high-performance glassy polymers reported previously. Furthermore, chemical modifications of the parent PIM-1 strongly affected the swelling magnitude. By investigating the behavior of relative refractive index, nrel, it was possible to study the interplay between micropores filling and matrix expansion. Remarkably, all studied PIMs showed a maximum in nrel at swelling of 2-2.5% indicating a threshold point above which the dissolution in the dense matrix started to dominate over sorption in the micropores. At pressures above 25 bar, all PIMs significantly plasticized in compressed CO2 and for the ones with the highest affinity to the penetrant, a liquidlike mixing typical for rubbery polymers was observed. Reduction of film thickness below 100 nm revealed pronounced nanoconfinement effects and resulted in a large swelling enhancement and a quick loss of the ultrarigid character. On the basis of the partial molar volumes of the dissolved CO2, the effective reduction of the Tg was estimated to be ∼200 °C going from 128 to 7 nm films.

Synthesis of Highly Gas-Permeable Polyimides of Intrinsic Microporosity Derived from 1,3,6,8-Tetramethyl-2,7-diaminotriptycene

A simple synthetic route to a novel sterically hindered triptycene-based diamine, 1,3,6,8-tetramethyl-2,7-diaminotriptycene (TMDAT), and its use in the preparation of high molecular weight polyimides of intrinsic microporosity (PIM-PIs) are reported. The organosoluble TMDAT-derived polyimides displayed high Brunauer–Emmett–Teller surface areas ranging between 610 and 850 m2 g–1 and demonstrated excellent thermal stability of up to 510 °C. Introduction of the rigid three-dimensional paddlewheel triptycene framework and the tetramethyl-induced restriction of the imide bond rotation resulted in highly permeable polyimides with moderate gas-pair selectivity. The best performing polyimide made from TMDAT and a triptycene-based dianhydride showed gas transport properties located between the 2008 and 2015 polymer permeability/selectivity trade-off curves with H2 and O2 permeabilities of 2858 and 575 barrer combined with H2/N2 and O2/N2 selectivities of 24 and 4.8, respectively, after 200 days of physical aging.