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A novel potentiometric sensor for carbon dioxide (CO2) detection utilizing a composite membrane of Polymer of Intrinsic Microporosity (PIM‐1) and 18‐diazabicyclo[5.4.0]undec‐7‐ene imidazolate (DBU‐imidazolate) is presented. The high surface area and gas permeability of PIM‐1, combined with the chemical affinity and ion‐exchange properties of DBU‐imidazolate, contribute to enhanced CO2 sensitivity and selectivity. The research objectives included the synthesis of PIM‐1 and DBU‐imidazolate, the preparation of composite membranes, and the evaluation of their performance as CO2 sensors. Solvent casting and impregnation methods are employed to prepare the membranes, which are characterized using Thermal Gravimetric Analysis (TGA), and Field Emission Scanning Electron Microscopy (FESEM). CO₂ absorption tests and Electrochemical Impedance Spectroscopy (EIS) are conducted to assess the sensors' performance. The PIM‐1/DBU‐imidazolate membrane exhibited high efficiency in CO₂ capture and release. Open circuit voltage (OCV) measurements are performed under varying concentrations of CO2 exposure and cycles of adsorption/desorption. Results show that the membrane achieves steady state faster at higher CO2 concentrations, with a logarithmic relationship between CO2 concentration and voltage variation, indicating potential for CO2 detection in human environments. These results confirm the sensor's ability to detect varying CO2 concentrations, highlighting its potential for reliable and efficient CO2 monitoring in environmental and industrial applications. [ABSTRACT FROM AUTHOR]

Monosaccharides are vital building blocks in bioengineering applications; however, their extraction from intricate mixtures is challenging and uses substantial amounts of energy. Polymers of intrinsic microporosity (PIMs) offer an innovative avenue for separating monosaccharides. We modified PIM‐1membranes to improve the glucose/xylose separation by incorporating polyethylene glycol monomethyl ether (mPEG). The optimal mPEG (molecular weight: 1000 Da; mass fraction: 2.5 %; solvent: methanol) delivered a xylose separation coefficient of 2.62. With the hybrid membrane of PIM‐1‐mPEG (50 w.t.%) and hydrophilic Tröger's base polymerer (DMBP‐TB, 50 w.t.%), the separation factor for xylose/glucose in an aqueous solution was 2.51 for single‐stage running and 11.32 after five‐stage running. There are large fractions of micropores for PIM‐1‐mPEG, and there is difference on solute‐membrane interactions for pentose/hexose, which are regarded to be the main driving force for the high pentose/hexose selectivity in methanol. The blending of PIM‐1‐mPEG and DMBP‐TB, integrates the microporosity and hydrophilicity, finally endues the high pentose/hexose selectivity in aqueous solution. These microporous membranes are promising materials for efficiently separating monosaccharides and jnl> small organic molecules while minimizing energy consumption. We established a solid foundation for further exploring microporous membranes for various applications, notably in bioengineering. [ABSTRACT FROM AUTHOR]

Superglassy membranes synthesised by polymers of intrinsic microporosity (PIMs) suffer from physical aging and show poor gas permeance over time, especially thin membranes, due to the fast rearrangement of nonequilibrium polymer chains. Herein, we constructed a novel PIM‐1 thin film nanocomposite membrane (TFN) using nanosized UiO‐66−NH2 (≈10 nm)/carboxylated PIM‐1 (cPIM‐1) as the composite filler. Unlike conventional fillers, which interact with the polymer only via the surface, the UiO‐66−NH2/cPIM‐1 forms a stable three‐dimensional (3D) network intertwining with the polymer chains, being very effective to impede chain relaxation, and thus physical aging. Nanosizing of UiO‐66−NH2 was achieved by regulating the nucleation kinetics using carbon quantum dots (CQD) during the synthesis. This led to increased surface area, and hence more functional groups to bond with cPIM‐1 (via hydrogen bonding between −NH2 and −COOH groups), which also improved interfacial compatibility between the 3D network and polymer chains avoiding defect formation. As a result, the novel TFN showed significantly improved performance in gas separation along with reduced aging (i.e. ≈6 % loss in CO2 permeability over 63 days); the aged membranes had a CO2 permeance of 2504 GPU and ideal selectivity values of 37.2 and 23.8 for CO2/N2 and CO2/CH4, respectively. [ABSTRACT FROM AUTHOR]

Polymers of intrinsic microporosity (PIMs) are a class of microporous organic materials that contain interconnected pores of less than 2 nm in diameter. Such materials are of great potential used in membranes for molecular separation, such as drug fractionation in pharmaceutical industry. However, the PIMs membranes are often susceptible to low separation selectivity toward different molecules due to their wide pore size distribution. Herein, a linear polyimide, Matrimid, is incorporated with PIM‐1 (a typical member of PIMs) by solution blending, and the blends are dip‐coated onto a polyimide P84 support membrane to prepare thin‐film composite (TFC) membranes to control pore size distribution while keep high microporosity. The component miscibility, pore characteristics, and molecular separation performances of the Matrimid/PIM‐1 TFC membranes are investigated in detail. The Matrimid and PIM‐1 are partially miscible due to their similar Hansen solubility parameters. The Matrimid endows the selective layers (coatings) with narrower pore size distribution due to more compact chain packing. The prepared Matrimid/PIM‐1 TFC membranes show high selectivity for separation of riboflavin (80% of retention) and isatin (only 5% of retention). The developed membranes exhibit great potential for separating molecules with different molecular weights. [ABSTRACT FROM AUTHOR]

• Solution processable PIMs were synthesized and applied for silver removal. • High Ag+ capacity and selectivity were obtained. • Excellent antibacterial ability was achieved as surface coatings. • Dissolution-separation-precipitation (DSP) approach was proven for adsorbent regeneration. • Distinguished renewability after fouling. Silver ions (Ag+) in waterways pose a growing threat to the environment and living organisms. Achieving an effective and green process for Ag+ removal requires an adsorbent with excellent specificity for silver ions and easy recoverability after fouling or blocking. However, this remains a major challenge. To address this concern, we developed a high-performance adsorbent by grafting polymers of intrinsic microporosity (PIM) with thioamide groups. This thioamide-modified PIM (TPIM-1) adsorbent exhibited an exceptional adsorption capacity of 656 mg g−1 and high selectivity (distribution coefficient of 833.3 mL g−1, selectivity coefficient of 346 over Cd2+) for aqueous Ag+ removal. TPIM-1 also features good solubility in selected solvents, allowing regeneration through a dissolution separation precipitation (DSP) procedure once fouling or blocking occurs. Over 80 % of the adsorption capacity was recovered after nine continuous regeneration cycles, showcasing potential cost-effective reusability. Density Functional Theory (DFT) results reveal that the grafted thioamide groups play a critical role in selective Ag+ adsorption, with a binding energy of 54 kcal mol−1. In addition, the Ag+-loaded PIM-coated glass surface showed excellent antibacterial ability, inhibiting the growth of Bacillus subtilis and E. coli. This study provides a viable strategy for the development of a low-carbon footprint silver removing adsorbent from wastewater. [ABSTRACT FROM AUTHOR]

• Calixarene decorated polymers of intrinsic microporosity were synthesized for lithium isotopes separation. • Excellent lithium adsorption capacity and lithium isotopes separation factor in aqueous phase were achieved. • The tert -butyl group on the upper rim of calixarene favors lithium adsorption and isotopes separation. Due to the importance of lithium isotopes in the nuclear energy industry, there are increasing number of researchs on the lithium isotopes separation in recent years. However, the adsorbents used for lithium isotopes separation suffer from the low adsorption capacity and isotopes separation factor in aqueous phase, and is difficult to meet the requirements for industrial lithium isotopes production. In this work, two types of calix[4]arenes with different rim groups were incorporated into the polymer backbone. Both calix[4]arene decorated PIMs exhibited good lithium adsorption capacities in aqueous phase. Among them, 4- tert -butyl-calix[4]arene decorated PIM showed excellent lithium isotopes separation performance with a maximum lithium adsorption capacity of 67.99 mg·g−1 and an isotopes separation factor of 1.034 ± 0.003 in aqueous phase. The ease of preparing and stable cycling performance makes it potentially useful for industrial lithium isotopes production. [ABSTRACT FROM AUTHOR]

Utilizing polymers of intrinsic microporosity (PIMs) to construct microporous membranes with high free volume fraction and surface area is a promising strategy to realize high-performance carbon capture. However, plasticization and physical aging remarkably limits the practical applications of PIM-based membrane separation. This work proposed a pore-compensation crosslinking strategy to fabricate a crosslinked microporous membrane with firmly inter-/intra-chain arrangement and highly-preserved CO 2 permeation for efficient and long-term gas separation. Amino-functionalized UiO-66 (UiO-66-NH 2) was employed to play the dual-function of crosslinker and pore compensation in the construction of crosslinking network among the bromomethylated PIM (BM-PIM) matrix via multiple covalent-crosslinking reactions. Compared with conventional crosslinking agents, the porous structure of UiO-66-NH 2 crosslinkers provided additional gas transport channels for compensating the reduction of free volume during the formation of crosslinking network. Meanwhile, the unsaturated metal sites on UiO-66-NH 2 crosslinkers enhanced the CO 2 transport. Accordingly, the crosslinked microporous membrane with pore compensation achieved an excellent gas separation (CO 2 /N 2 and CO 2 /CH 4 separation factors of 32.2 and 49.3) and structural stability with superior anti-plasticization (plasticizing pressure up to 0.8 MPa) and anti-aging (CO 2 permeability loss <15 % after 180 days). The pore-compensation crosslinking strategy offers a novel method to fabricate high-performance microporous membrane for efficient carbon capture. [Display omitted] • A pore-compensation crosslinking strategy was proposed to prepare PIMs membrane. • Defective UiO-66-NH 2 played the dual-function of crosslinker and pore compensation. • Inter/intra-molecular crosslinking network within membranes enhanced the stability. • Pore compensation by UiO-66-NH 2 among membranes preserved highly CO 2 permeability. [ABSTRACT FROM AUTHOR]

The ZIF‐8@Agmim core‐shell hybrid material was synthesized via a favorable post‐modification method of ion exchange (PMIE). This infrequent ZIF‐8@Agmim core‐shell structure maintains a well‐integrated pore size that is almost the same as ZIF‐8. The similar equilibrium isotherms with ZIF‐8 and better kinetic separation toward propylene/propane than ZIF‐8 render ZIF‐8@Agmim to be an interesting candidate for propylene/propane separation. The core‐shell hybrid nanomaterial was further used as nanofillers in the polymer of intrinsic microporosity matrix (PIM‐1) for propylene/propane separation. The resultant mixed‐matrix membranes (MMMs) exhibited a simultaneous increase in C3H6 permeability and C3H6/C3H8 ideal selectivity compared to pure polymer membrane owing to a synergistic effect of molecular sieving from ZIF‐8 and π‐complexation of Ag+ with propylene. The separation performance of the prepared MMM surpasses the upper bound line of polymer membranes. Furthermore, the hybrid materials possess superb photochemical stability and the corresponding MMMs exhibit excellent anti‐aging property and long‐term stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • PP@oPIM-1 was synthesized via a one-pot Friedel-Crafts alkylation reaction. • A 3D network structure composed of oPIM-1 existed on the surface of PP@oPIM-1. • For MMMs, interweaving structures between PP@oPIM-1and polymer matrix was formed. • Such robust interweaving structure facilitated the interfacial compatibility. • The obtained MMM shows a significantly improved permeability and selectivity. The trade-off limitation between permeability and selectivity has hindered the widespread applications of polymer membranes. The integration of solid fillers into polymer membranes, namely the development of mixed-matrix membranes (MMMs), can overcome the trade-off effect, serving as an effective method to fabricate high-performance membranes. Porous organic polymer of PP, made from dichloro- p -xylene via Friedel-Crafts alkylation reaction, is excellent candidate for MMMs fabrication. However, tailoring PP for membrane CO 2 separation with desirable performance is still a challenge. Herein, we report the development of a functionalized PP, namely PP@oPIM-1, which is achieved by covalently grafting PIM-1 oligomers (oPIM-1) on the surface of PP. This functionalized product is used as a filler material to construct MMMs. Compared to PP-loaded MMMs, the MMMs containing PP@oPIM-1 filler demonstrate improved interfacial adhesion. Thanks to the excellent interfacial compatibility, the tensile strength of 10 wt% PP@oPIM-1/Matrimid is 59.29 MPa, which is higher than 30.24 MPa and 54.06 MPa for 10 wt% PP/Matrimid and pure Matrimid membrane, respectively. Meanwhile, the interweaving structures between oPIM-1 network on the surface of PP@oPIM-1 and polymer chains of matrix lead to the formation of highly interconnected paths between two phases, which is beneficial to fully demonstrating the advantages of filler in selective permeation of gas molecules. As such, the 10 wt% PP@oPIM-1/Matrimid membrane displays a CO 2 permeability of 17.4 Barrer and CO 2 /N 2 selectivity of 46.7, which are increased by 104.7 % and 51.1 % compared to the bare Matrimid membrane. Additionally, the broad applicability of PP@oPIM-1 in various polymer matrices, such as 6FDA-DAM polyimide and PIM-1, has also been explored. [ABSTRACT FROM AUTHOR]

The prototypical polymer of intrinsic microporosity, PIM-1, was synthesized with branched topology, then acid-hydrolyzed to introduce carboxylic acid functional groups (cPIM-1). Self-standing membranes and thin film nanocomposite (TFN) membranes were fabricated from PIM-1, cPIM-1, and Ni- or Co-MOF-74 nanoparticles (NPs), with a particular focus on TFNs for industrial viability. TFN membranes on polyacrylonitrile support were fabricated utilizing the following methods: (i) conventional blending; (ii) a grafting reaction between the hydroxyl group in the MOF-74 NPs and fluoro-groups of the chain-ends during PIM-1 synthesis; and (iii) an in-situ cross-linking reaction between the carboxylic acid groups in cPIM-1 and the metal ions of MOF-74 synthesized in-situ. Both conventional blending and grafting of PIM-1 with MOF-74 showed significant increase in permeance in TFN membranes. A grafted PIM-1 TFN membrane produced a CO 2 permeance of 9600 GPU, which is roughly 170 % higher than a pristine PIM-1 thin film composite (TFC) membrane, while also improving the selectivity. After 28 days of aging, a blended TFN membrane based on PIM-1 showed a CO 2 permeance of 1000 GPU and selectivities of 20.0 and 20.5 for CO 2 /N 2 and CO 2 /CH 4 , respectively. Crosslinked cPIM-1 TFNs showed significant improvement in ideal selectivity from 65 in cPIM-1 to over 90 for CO 2 /N 2 , with permeance almost unchanged after crosslinking with Ni-MOF-74. However, small differences in the polyacrylonitrile support can result in significant changes in gas separation behavior. In mixed gas conditions, crosslinked cPIM-1/Co-MOF-74 produced an impressive 1842 GPU and CO 2 /N 2 selectivity of 33. These results fall within the performance range that is suitable for post-combustion carbon capture. [Display omitted] • Grafting of MOF with PIM-1 gives more durable film than simple blend. • MMMs of cPIM-1 crosslinked with Co-MOF-74 exceed 2019 CO 2 /N 2 upper bound. • TFN membranes give performance in favorable region for CO 2 capture. • Nature of support affects performance of TFN membranes. [ABSTRACT FROM AUTHOR]

Continuous long-term evaluation of propylene and propane permeation through narrow slit carbon molecular sieve (CMS) membranes is essential for an in-depth study of their steady-state separation performance. CMS membranes are characterized by finely tuned ultramicroporous structures, exceptional thermal and chemical stability, and hold great promise for the energy-intensive separation of propylene and propane. However, the gradual changes in their performance over time due to penetrant-induced structural chain rearrangements have often been overlooked. In this study, we prepared CMS membranes using a polymer of intrinsic microporosity (PIM) with a highly aromatic tetraphenylethylene (TPE) based building block. The presence of bulky and sterically hindered TPE repeat units renders this polymer an excellent precursor for the fabrication of high-performance CMS membranes. The TPE-PIM-based precursor underwent pyrolysis at temperatures ranging from 550 to 700 °C for 1 h. Pure- and mixed-gas permeation tests were accompanied by various characterization techniques to assess the carbonization state of the CMS materials. The CMS pyrolyzed at 700 °C exhibited a decline in pure-gas C 3 H 6 /C 3 H 8 selectivity from an initial value of 300 to 161 at steady state over a 20-day period. Even more notable, under equimolar mixed-gas feed conditions, the isotropic CMS film displayed a substantial C 3 H 6 /C 3 H 8 selectivity reduction from 214 to 62 over a 24-day period. This performance decline can be attributed to competitive sorption and very slow dilation kinetics, which led to moderately reduced propylene permeability while significantly enhancing propane permeability. Our study suggests that long-term, continuously performed mixed-gas permeation experiments are essential to assess the 'steady-state' performance of CMS membranes for mixtures containing highly sorbing feed components, as observed for propylene/propane separation. [Display omitted] • TPE-PIM-derived CMS films require very long time to reach steady-state permeability for C 3 H 8. • Propane sorption at 1 bar in TPE-PIM-based CMS pyrolized at 600–700 °C requires ∼ 3–4 days to reach equilibrium. • Continuous long-term mixed-gas permeability experiments are essential to obtain reliable performance data for C 3 H 6 /C 3 H 8. • Steady-state mixed-gas C 3 H 6 permeability of 7.5 Barrer and C 3 H 6 /C 3 H 8 selectivity of 62 for TPE-PIM-700 °C after 24 days. [ABSTRACT FROM AUTHOR]

Capturing CO 2 from flue gas of coal-burned power plants has been considered to be a promising technology to mitigate the environmental problems caused by rising level of CO 2 at the atmosphere. Amine-functionalized adsorbents, showing impressive CO 2 adsorption capability and selectivity even at low CO 2 partial pressure, face the challenge of permanent structural changes and performance deterioration due to the irreversibly bonding of SO 2 , a common impurity of flue gas, particularly under humid condition. Besides, the reported amine-functionalized adsorbents are usually nano-sized powders, impractical for industrial applications. Therefore, the development of efficient, stable, and structured CO 2 adsorbents is still an urgent need. Herein, we develop a novel structured mixed-matrix adsorbent (PIM-PP-DETA), using a diethylenediamine-appended porous organic copolymer (PP-DETA, prepared by a copolymerization reaction of dichloro- p -xylene and 4,4′-bis(chloromethyl)biphenyl and a one-step amine grafting process) as main adsorbent and PIM-1 as polymer matrix through a phase inversion process. The as-developed PIM-PP-DETA not only exhibits high CO 2 adsorption capacity and outstanding CO 2 selectivity over N 2 , but also shows fast adsorption kinetics and high stability under repeated adsorption-desorption cycling under dynamic flow conditions. Furthermore, PIM-PP-DETA possesses high tolerance towards acidic and moist environments, with CO 2 adsorption capacity remained at a relatively high level after SO 2 and humid exposure, suggesting its potential usage to post-combustion CO 2 capture. [Display omitted] • PP-DETA was prepared from a porous organic copolymer by an amine grafting process. • PIM-PP-DETA was fabricated via a phase conversion process with PIM-1 as the matrix. • PIM-PP-DETA appeared as robust spherical beads with hierarchical porosity. • It showed outstanding CO 2 /N 2 separation performance and fast adsorption kinetics. • It possessed good cycling performance and high tolerance towards SO 2 and moist. [ABSTRACT FROM AUTHOR]

Recently, the polymers of intrinsic microporosity (PIMs) exhibit good potential in high-temperature proton exchange membrane fuel cells (HT-PEMFCs) due to their tunable microporosity and functionality. In this paper, alkaline pyrrolidine and piperidine functional groups were introduced onto PIM-1 via the classical Mannich reaction obtaining PIM-1/PIM-Py-50 and PIM-1/PIM-MePi-50. It was found that, compared with commercial Meta -polybenzimidazole (m -PBI) membrane, PIMs membranes showed superior retention of phosphoric acid (PA) and conductivity due to their grafting alkaline groups and rich micropores. After equilibration under 80 °C/40 % relative humidity (RH) for 150 h, the PA retention of PA doped PIM-1/PIM-Py-50 (PIM-1/PIM-Py-50/PA) and PA doped PIM-1/PIM-MePi-50 (PIM-1/PIM-MePi-50/PA) membranes were 74.13 % and 68.52 %, respectively, much higher than PA doped m -PBI (m -PBI/PA) (45.73 %). PIMs membranes maintain excellent dimensional and conductivity stability at 160 °C operating conditions, e.g. PIM-1/PIM-Py-50/PA membrane showed area swelling retention and volume swelling retention of 84.69 % and 82.19 % after 230 h at 160 °C. In addition, with the similar PA uptake, PIMs membranes displayed higher conductivity and peak power density (PPD) at 160 °C. In the accelerated stress test (AST) the PPD of the fuel cell (FC) with the PIM-1/PIM-Py-50/PA membrane remained 81.25 % after 200 aggressive start-up/shut-down cycles at 80 °C. Therefore, PIM-based membranes alkaline groups exhibit a wider temperature operating window, providing theoretical guidance for the design and study of the next generation of high-temperature proton exchange membranes (HT-PEMs). [Display omitted] • Polymers of intrinsic microporosity with alkaline functional groups were obtained. • PIM-1/PIM-Py-50 showed less swelling and better dimensional stability than m -PBI. • PA and peak power density retention of 74.13 % and 81.25 % for PIM-1/PIM-Py-50/PA. • PIM-1/PIM-Py-50/188 % PA has higher conductivity and peak power density than m -PBI/184 % PA. [ABSTRACT FROM AUTHOR]

• 3D-TB porous network and TB polymer were prepared under the same reaction system. • The in-situ crosslinking of TB to 3D-TB renders MMM with interfacial crosslinking. • The in-situ crosslinking enhances the mechanical properties of MMM. • The obtained MMM shows a significantly improved permeability and selectivity. The typical procedure used to fabricate mixed matrix membranes (MMMs), where the pre-obtained filler and polymer are simply mixed together before casting, often suffers from limited polymer-filler adhesion. Herein, we prepare a series of novel MMMs with improved interfacial compatibility by preparing the matrix (Tröger's base polymer, TB) and the filler (three-dimensional Tröger's base-bridged porous network, 3D-TB) under the same reaction system, where in-situ crosslinking reaction between them happens simultaneously. Thanks to the excellent interfacial miscibility, the as-developed 10 wt%_3D-TB@TB membrane shows the tensile strength and elongation stain at break of 65.4 MPa and 10.12 %, respectively, which are higher than those of its counterpart synthesized by conventional procedure (55.82 MPa and 7.05 %, respectively). More importantly, both the gas permeability and selectivity of the in-situ crosslinked MMMs show an obvious improvement involving CO 2 /N 2 , CO 2 /CH 4 , and O 2 /N 2 separation. Specifically, for O 2 /N 2 binary gas separation, the 10 wt%_3D-TB@TB membrane displayed a O 2 permeability of 53.2 Barrers and O 2 /N 2 selectivity of 6.1, which are improved by 72 % and 45 % in comparison to the unfilled membrane, overcoming the 2008 Robson upper bound. Moreover, the physical aging of the in-situ crosslinked MMMs is also effectively controlled. These results demonstrate that the in-situ polymerization and crosslinking is an outstanding approach for the construction of defect-free MMMs with enhanced gas separation performances. [ABSTRACT FROM AUTHOR]

In this work, thin film composite (TFC) membranes were fabricated with the selective layer based on a blend of polyimide Matrimid®5218 and polymer of intrinsic microporosity (PIM) composed of Tröger’s base, TB, and dimethylethanoanthracene units, PIM-EA(Me2)-TB. The TFCs were prepared with different ratios of the two polymers and the effect of the PIM content in the blend of the gas transport properties was studied for pure He, H2, O2, N2, CH4, and CO2 using the well-known time lag method. The prepared TFC membranes were further characterized by IR spectroscopy and scanning electron microscopy (SEM). The role of the support properties for the TFC membrane preparation was analysed for four different commercial porous supports (Nanostone Water PV 350, Vladipor Fluoroplast 50, Synder PAN 30 kDa, and Sulzer PAN UF). The Sulzer PAN UF support with a relatively small pore size favoured the formation of a defect-free dense layer. All the TFC membranes supported on Sulzer PAN UF presented a synergistic enhancement in CO2 permeance, and CO2/CH4 and CO2/N2 ideal selectivity. The permeance increased about two orders of magnitude with respect to neat Matrimid, up to ca. 100 GPU, the ideal CO2/CH4 selectivity increased from approximately 10 to 14, and the CO2/N2 selectivity from approximately 20 to 26 compared to the thick dense reference membrane of PIM-EA(Me2)-TB. The TFC membranes exhibited lower CO2 permeances than expected on the basis of their thickness—most likely due to enhanced aging of thin films and to the low surface porosity of the support membrane, but a higher selectivity for the gas pairs CO2/N2, CO2/CH4, O2/N2, and H2/N2.

The electrospinning of high-performance polyimides (PI) has recently sparked great interest. In this study, we explore the effect of the electrospinning parameters — namely polymer concentration, voltage, tip-to-collector distance and flow rate — and salt addition on the diameter, morphology, and spinnability of electrospun PI nanofibers. Three different polyimides of intrinsic microporosity (PIM-PIs) with high Brunauer–Emmett–Teller (BET) ranging from 270 to 506 m2 g−1, and two microporous polyimides, were synthesized through the polycondensation of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and aromatic diamines. The addition of tetraethylammonium bromide (TEAB) salt considerably increased the conductivity of all the PI solutions, significantly improved spinability, and resulted in thinner fibers. We also used molecular dynamic simulations to investigate the macromolecular mechanism of improved spinnability and fiber morphology in the presence of an ammonium salt. The small droplets detached from the parent droplet, followed by the rapid evaporation of the ions through the hydration effect, which facilitated the electrospinning. The resulting uniform nanofibers have great potential in environmental applications due to the presence of microporosity and hydrophobic pendant trifluoromethyl groups, which enhance the sorption performance of the fibers for hydrophobic species.

A spirobifluorene polymer of intrinsic microporosity (PIM-SBF) and polyphenylene networks based on triphenylbenzene (TPB), hexaphenylbenzene (HPB) and octaphenylquinquephenyl (OPQ) were synthesised and characterized. Uncrosslinked membranes of PIM-SBF proved suitable for the separation of a toluene/DMSO mixture (77:23 volume ratio) by pervaporation at 65°C, giving a separation factor of 3.9 and a flux of 2.0 kg m-2 h-1. The addition of 5 wt% HPB network enhanced the separation factor, while OPQ and TPB networks increased the flux that could be achieved. [ABSTRACT FROM AUTHOR]

A detailed investigation has been carried out of the pre-polymerisation modification of the polymer of intrinsic microporosity PIM-1 by the addition of two methyl (Me) groups to its spirobisindane unit to create a new chemically modified PIM-1 analogue, termed MePIM. Our work explores the effects of this modification on the porosity of PIM-1 and hence on its gas sorption properties. MePIM was successfully synthesised using either low (338 K) or high (423 K) temperature syntheses. It was observed that introduction of methyl groups to the spirobisindane part of PIM-1 generates additional microporous spaces, which significantly increases both surface area and hydrogen storage capacity. The BET surface area (N2 at 77 K) was increased by ~ 12.5%, resulting in a ~ 25% increase of hydrogen adsorption after modification. MePIM also maintains the advantages of good processability and thermal stability. This work provides new insights on a facile polymer modification that enables enhanced gas sorption properties. [ABSTRACT FROM AUTHOR]

Gas separation properties are reported for self-standing polymer of intrinsic microporosity (PIM) films after addition of palladium (II) acetate or iron (II) acetate by solid state or liquid state mixing. Membranes, with thicknesses in the range 35–55 μm, were prepared from three high molar mass PIMs, two different branched versions of the much-reported PIM-1 (PIM-1a and PIM-1b) and of PIM-Py. Addition of either Fe(OAc) 2 or Pd(OAc) 2 to all three PIMs led to a reduction in permeability and increase in selectivity, but the permeability reduction was much greater for Pd(OAc) 2 , which is able to interact with branch points in the PIM and crosslink the polymer. CO 2 /CH 4 selectivity of membranes containing Pd(OAc) 2 was poor upon aging, especially after solid state addition to the PIM-1 polymers, for which CO 2 permeabilities dropped to below 200 Barrer after 85 days. Hydrogen permeability and H 2 /N 2 selectivity of membranes containing Pd(OAc) 2 did more closely follow conventional permeability/selectivity trade off upon aging. This illustrates the profound differences that can arise in gas permeation properties and aging behaviour from variations in chemical structure and macromolecular characteristics, and from the addition of metal acetates that interact with the polymer in different ways. [Display omitted] • Branched PIM-1 crosslinked with Pd(OAc) 2 produced membranes with reduced permeability. • Loss in CO 2 permeability on aging not matched with increase in CO 2 /CH 4 selectivity. • Loss in H 2 permeability on aging matched with increase in H 2 /N 2 selectivity. • Crosslinks block smaller free volume elements that dominate CO 2 /CH 4 selectivity. • Fe(OAc) 2 mixed PIM-1 membranes maintain permeability/selectivity balance. [ABSTRACT FROM AUTHOR]

Nowadays, nanofiltration is widely used for water treatment due to its advantages, such as energy-saving, sustainability, high efficiency, and compact equipment. In the present work, novel nanofiltration membranes based on the polymer of intrinsic microporosity PIM-1 modified by metal-organic frameworks (MOFs)—MIL-140A and MIL-125—were developed to increase nanofiltration efficiency for the removal of heavy metal ions and dyes. The structural and physicochemical properties of the developed PIM-1 and PIM-1/MOFs membranes were studied by the spectroscopic technique (FTIR), microscopic methods (SEM and AFM), and contact angle measurement. Transport properties of the developed PIM-1 and PIM-1/MOFs membranes were evaluated in the nanofiltration of the model and real mixtures containing food dyes and heavy metal ions. It was found that the introduction of MOFs (MIL-140A and MIL-125) led to an increase in membrane permeability. It was demonstrated that the membranes could be used to remove and concentrate the food dyes and heavy metal ions from model and real mixtures.

Superglassy membranes synthesised by polymers of intrinsic microporosity (PIMs) suffer from physical aging and show poor gas permeance over time, especially thin membranes, due to the fast rearrangement of nonequilibrium polymer chains. Herein, we constructed a novel PIM-1 thin film nanocomposite membrane (TFN) using nanosized UiO-66-NH 2 (≈10 nm)/carboxylated PIM-1 (cPIM-1) as the composite filler. Unlike conventional fillers, which interact with the polymer only via the surface, the UiO-66-NH 2 /cPIM-1 forms a stable three-dimensional (3D) network intertwining with the polymer chains, being very effective to impede chain relaxation, and thus physical aging. Nanosizing of UiO-66-NH 2 was achieved by regulating the nucleation kinetics using carbon quantum dots (CQD) during the synthesis. This led to increased surface area, and hence more functional groups to bond with cPIM-1 (via hydrogen bonding between -NH 2 and -COOH groups), which also improved interfacial compatibility between the 3D network and polymer chains avoiding defect formation. As a result, the novel TFN showed significantly improved performance in gas separation along with reduced aging (i.e. ≈6 % loss in CO 2 permeability over 63 days); the aged membranes had a CO 2 permeance of 2504 GPU and ideal selectivity values of 37.2 and 23.8 for CO 2 /N 2 and CO 2 /CH 4 , respectively., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The electrochemical reduction of CO 2 to give CO in the presence of O 2 would allow the direct valorization of flue gases from fossil fuel combustion and of CO 2 captured from air. However, it is a challenging task because O 2 reduction is thermodynamically favored over that of CO 2. 5% O 2 in CO 2 near catalyst surface is sufficient to completely inhibit the CO 2 reduction reaction. Here we report an O 2 -tolerant catalytic CO 2 reduction electrode inspired by part of the natural photosynthesis unit. The electrode comprises of heterogenized cobalt phthalocyanine molecules serving as the cathode catalyst with >95% Faradaic efficiency (FE) for CO 2 reduction to CO coated with a polymer of intrinsic microporosity that works as a CO 2 -selective layer with a CO 2 /O 2 selectivity of ∼20. Integrated into a flow electrolytic cell, the hybrid electrode operating with a CO 2 feed gas containing 5% O 2 exhibits a FE CO of 75.9% with a total current density of 27.3 mA/cm2 at a cell voltage of 3.1 V. A FE CO of 49.7% can be retained when the O 2 fraction increases to 20%. Stable operation for 18 h is demonstrated. The electrochemical performance and O 2 tolerance can be further enhanced by introducing cyano and nitro substituents to the phthalocyanine ligand. [ABSTRACT FROM AUTHOR]

• A synthetic strategy for hydrophobic polymer pervaporation membrane is presented. • The membrane has the hierarchical structure of micropores-micropores-mesopores. • The membrane shown high permeability and selectivity for dehydration of alcohols. Pervaporation is a promising membrane technology for separation of aqueous organic solution particularly azeotrope and close-boiling point compounds. However, most of pervaporation membranes are based on hydrophilic polymers that suffer decline of separation performance due to their swelling in aqueous solution. Here we present a copolymer synthetic strategy for preparation of hydrophobic polymer pervaporation membrane with hierarchical porosity via uniting both rigid and flexible segments. The synthesized membrane has well-defined micropores and high free volume faction of 8.03% with cavity size of 0.476 nm, and demonstrate exceptional performance with high permeability and selectivity for dehydration of alcohols. In the pervaporation of ethanol-water azeotrope, the membrane displays the high permeabtion flux of 74.6 μm kg m−2 h−1 and water selectivity of 34 (separation factor of 732) at 30 °C. The developed strategy has excellent potential for synthesizing copolymers for high-efficient pervaporation membranes. [ABSTRACT FROM AUTHOR]

Polymer of intrinsic microporosity PIM-1 was used for electrospun polymer nanofiber producing. After pyrolysis, the obtained nanofibers, in a form of entire mat, were used as a support for cathode electrocatalyst for high-temperature polymer electrolyte membrane fuel cell on polymer polybenzimidazole membrane. The material was characterized by the methods of standard contact porosimetry, Raman spectroscopy and scanning electron microscopy. The I-V curves for membrane-electrode assembly suggest a possibility of using the carbon material for electrodes in a fuel cell on polymer membrane. [ABSTRACT FROM AUTHOR]

The exploration and evaluation of new composites possessing both processability and enhanced hydrogen storage capacity are of significant interest for onboard hydrogen storage systems and fuel cell based electric vehicle development. Here we demonstrate the fabrication of composite membranes with sufficient mechanical properties for enhanced hydrogen storage that are based on a polymer of intrinsic microporosity (PIM-1) matrix containing nano-sized fillers: activated carbon (AX21) or metal–organic framework (MIL-101). This is one of the first comparative studies of different composite systems for hydrogen storage and, in addition, the first detailed evaluation of the diffusion kinetics of hydrogen in polymer-based nanoporous composites. The composite films were characterised by surface area and porosity analysis, hydrogen adsorption measurements, mechanical testing and gas adsorption modelling. The PIM-1/AX21 composite with 60 wt% AX21 provides enhanced hydrogen adsorption kinetics and a total hydrogen storage capacity of up to 9.35 wt% at 77 K; this is superior to the US Department of Energy hydrogen storage target. Tensile testing indicates that the ultimate stress and strain of PIM-1/AX21 are higher than those of the MIL-101 or PAF-1 containing composites, and are sufficient for use in hydrogen storage tanks. The data presented provides new insights into both the design and characterisation methods of polymer-based composite membranes. Our nanoporous polymer-based composites offer advantages over powders in terms of safety, handling and practical manufacturing, with potential for hydrogen storage applications either as means of increasing storage or decreasing operating pressures in high-pressure hydrogen storage tanks. [ABSTRACT FROM AUTHOR]

Abstract An understanding of gas transport in polymers of intrinsic microporosity (PIMs) is limited by a lack of directly determined (experimental) sorption data and by quantitative inaccuracies in solubilities calculated indirectly from permeation time-lag analysis. To address this, we provide a detailed gas sorption analysis for seven different PIMs and assess the influence of the non-linear steady-state CO 2 concentration profiles on the apparent solubilities obtained from permeation experiments. Equilibrium sorption was analyzed with dual-mode sorption (DMS) and Guggenheim, Anderson and De Boer (GAB) models, which provided accurate descriptions of the data. The non-linear steady-state CO 2 concentration profiles were calculated using the thermodynamic Fick's law based on the DMS or GAB model coefficients. Once the thermodynamic term was incorporated into the model for permeation, better agreement between directly (gravimetric sorption) and indirectly (time-lag analysis) determined solubility was observed for most membranes. The monolayer capacities were found to be linearly dependent between the models and could be used for a qualitative comparison of the apparent surface area of PIM materials. Diffusivities determined from time-lag analysis were higher (e.g., PIM-Trip-TB, CO 2 , 111·10−8 m2 s−1) than those from sorption measurements (24·10−8 m2 s−1), probably due to substantially low mass uptake in Henry mode (11% of total sorption capacity). Thus, a careful gas sorption analysis in combination with time lag experiments provides a deeper insight into the transport behavior of gases in PIMs than when only time lag measurements are performed. Graphical abstract fx1 Highlights • Sorption of gases in seven polymers of intrinsic microporosity. • CO 2 solubility from time-lag analysis is overestimated in most of the PIMs. • Thermodynamic Fick's law allows for the correction of the solubility. • Apparent surface areas based on DMS, GAB and BET models are comparable and highly correlated. [ABSTRACT FROM AUTHOR]

Abstract Polymers of intrinsic microporosity, such as PIM-1, advantageously combine high surface areas with good processability, which are attractive properties for hydrogen storage applications. Here we address the lack of data on the long-term mechanical stability and hydrogen uptake capacity of PIM-1 in a study carried out over 400 days. Our results show that most mechanical and surface properties of PIM-1 remain stable over this time. In particular, the mechanical strength and elasticity are maintained, and the surface area remains constant over the course of our observations. In contrast, we detected a small but statistically significant decrease of the hydrogen storage capacity of the material over time, particularly in the first stages of aging. We attribute this phenomenon to the slow rearrangement of the polymer scaffold in the solid state. Taken together, our experiments demonstrate that PIM-1 possesses the long-term stability required for realistic applications in hydrogen storage or in gas separation. Highlights • Thin films made of microporous polymer PIM-1 were monitored over 400 days. • The mechanical properties (strength and elasticity) are maintained. • The surface properties (surface area) remain constant. • The hydrogen uptake (up to 10 MPa) slightly decreases over time. • The stability of PIM-1 makes it a promising material for long-term hydrogen storage. [ABSTRACT FROM AUTHOR]

• Preparation of highly selective 3-(trimethoxysilyl)propan-1-aminium acetate and PIM-1 based membrane. • Up to 58.62% and 40.11% increase in CO 2 /CH 4 and CO 2 /N 2 selectivity respectively compared to the pristine membrane. • The selectivity increases attributed to the strong interaction and high solubility of CO 2 in the RTIL. Blend membranes were fabricated by incorporating an ionic liquid, 3-(trimethoxysilyl) propan-1-aminium acetate ([APTMS][Ac]), as a filler into the polymer of intrinsic microporosity PIM-1. The analyses using FTIR spectroscopy, AFM, and SEM confirmed a uniform dispersion and excellent polymer-filler compatibility, even at higher loadings. Gas transport properties were assessed with filler loadings up to 10 wt% of IL, revealing a slight reduction in permeability but an enhancement in selectivity. CO 2 permeability of the blend membrane decreased by 37% at 10% filler loading, while the ideal selectivity increased from 19.6 to 29.0 for CO 2 /CH 4 and from 20.9 to 31.7 for CO 2 /N 2 upon increasing [APTMS][Ac] content (0 wt% − 10 wt%). The CO 2 /CH 4 gas mixture selectivity rose by 58.62% and the CO 2 permeability dropped by 40.44% compared to the pristine PIM-1 membrane. For the CO 2 /N 2 gas mixture, the selectivity and CO 2 permeability were enhanced by 40.11% and reduced by 39.07%, respectively. The permeability reduction can be ascribed to the filling of free volume voids in the PIM-1 polymer matrix by the IL [APTMS][Ac], while the selectivity improvement can be attributed to the strong interaction and high solubility of CO2 in the ionic liquid. The CO 2 solubility coefficient increased with the rising IL concentration, indicating the high solubility of the IL in the polymer matrix. [ABSTRACT FROM AUTHOR]

High free-volume copolymers were prepared via polycondensation with 2,3,5,6,-tetrafluoroterephthalonitrile (TFTPN) in which a portion of the 3,3,3',3'-tetramethyl-1,1'-spirobisindane (TTSBI) of PIM-1 was replaced with dibutyl anthracene maleimide (4bIII). An investigation of free volume using positron annihilation lifetime spectroscopy (PALS), and gas permeation measurements was carried out for the thin film composite copolymer membranes and compared to PIM-1. The average free volume hole size and the gas permeance of the copolymer membranes increased with decreasing TTSBI content in the copolymer.

Poor interfacial compatibility remains a pressing challenge in the fabrication of high-performance polymer-MOF composites. In response, introducing compatible chemistries such as a carboxylic acid moiety has emerged as a compelling strategy to increase polymer-MOF interactions. In this work, we leveraged compatible functionalities in UiO-66-NH 2 and a carboxylic acid-functionalized PIM-1 to fabricate mixed-matrix membranes (MMMs) with improved separation performance compared to PIM-1-based MMMs in industrially relevant conditions. Under pure-gas conditions, PIM-COOH-based MMMs retained selectivity with increasing MOF loading and showed increased permeability due to increased diffusion. The composites were further investigated under industrially relevant conditions, including CO 2 /N 2 , CO 2 /CH 4 , and H 2 S/CO 2 /CH 4 mixtures, to elucidate the effects of competitive sorption and plasticization. Incorporation of UiO-66-NH 2 in PIM-COOH and PIM-1 mitigated the effects of CO 2 - and H 2 S-induced plasticization typically observed in linear polymers. In CO 2 -based binary mixed-gas tests, all samples showed similar performance as that in pure-gas tests, with minimal competitive sorption contributions associated with the amine functional groups of the MOF. In ternary mixed-gas tests, improved plasticization resistance and interfacial compatibility resulted in PIM-COOH-based MMMs having the highest H 2 S/CH 4 and CO 2 /CH 4 selectivity combinations among the films tested in this study. These findings demonstrate that selecting MOFs and polymers with compatible functional groups is a useful strategy in developing high-performing microporous MMMs that require stability under complex and industrially relevant conditions.

High permeance membranes were produced by addition of highly permeable nanoparticulate fillers (hypercrosslinked polystyrene, HCP, and its carbonized form, C-HCP) to a high free volume polymer (polymer of intrinsic microporosity PIM-1) in a thin film (typically 2 µm) on a porous polyacrylonitrile support. Self-standing mixed matrix membranes (MMMs) of thicknesses in the range 40–90 µm were also prepared with the same polymer and fillers. While robust MMMs could only be formed for moderate filler loadings, thin film nanocomposite (TFN) membranes could be produced from dispersions with filler loadings up to 60 wt%. On increasing the filler loading, CO 2 permeance increased in line with the predictions of the Maxwell model for a highly permeable filler. Physical ageing led to some loss of permeance coupled with an increase in CO 2 /N 2 selectivity. However, for TFN membranes the greatest effects of ageing were seen within 90 days. After ageing, TFN membranes showed high permeance with reasonable selectivity; for example, with 60 wt% C-HCP, CO 2 permeance > 9300 GPU, CO 2 /N 2 selectivity ~ 11. [ABSTRACT FROM AUTHOR]

The purification of benzene derivatives, particularly xylene isomers, is one of the most important organic mixture separations practiced in industry. The separation of xylene isomers is especially challenging due to the similarity of their physical properties. Carbon molecular sieve (CMS) membranes are promising materials for such challenging solvent separations due to their thermal and chemical stability, but these materials have not been studied in detail in the case of large organic molecules. Xylene isomer transport and sorption properties in a CMS membrane derived from a prototypical polymer of intrinsic microporosity (PIM-1) reveal that diffusion selectivity is the dominant factor in contributing to the preferential permeation of p-xylene over o-xylene. Moreover, the contributions of “enthalpic” and “entropic” selectivity to the diffusion selectivity are studied in detail and reveal that entropic factors dominate the xylene selection mechanism. Overall, this study provides fundamental insight and guidance into the separation of large organic molecules in amorphous microporous materials. [ABSTRACT FROM AUTHOR]

Physical aging of polymer of intrinsic microporosity PIM-1 is one of the major obstacles for its application as a commercial membrane material for gas separation. In this work, physical aging of PIM-1 and matrices of this same polymer containing graphene-like materials were studied. Graphene-like fillers resulted from the functionalization of graphene oxide (GO) with two alkyl chains of different lengths, using octylamine (OA) and octadecylamine (ODA), and further chemical reduction. Extents of membrane aging were evaluated through changes in gas permeability over time; the separation of gas mixtures comprising carbon dioxide and methane, which are of great interest for industrial applications such as the production of biogas or the purification of natural gas, was carried out. 50:50 vol% CO 2 /CH 4 mixtures were used as feed and separation performance analysed for fresh membranes and at intervals of approximately a month up to 155 days. At the end of this testing period, aged PIM-1 membranes showed a CO 2 permeability of (2.0 ± 0.7) × 10 3 Barrer, which corresponds to a CO 2 permeability reduction of 68% from the value obtained right after their fabrication. The addition of alkyl-functionalized GO is shown to be an efficient strategy to retard the physical aging of PIM-1 membranes; filler loadings as low as 0.05 wt% of reduced octyl-functionalized GO showed a CO 2 permeability of (3.5 ± 0.6) × 10 3 Barrer after 5 months, which is almost three quarters higher than that of pure PIM-1 membrane aged for the same time period and represents a reduction of just 39% from its initial value. Moreover, the addition of graphene-like materials to PIM-1 does not affect its mechanical properties. [ABSTRACT FROM AUTHOR]

PIM-1, PIM-7, and PIM-8 composite membranes have been fabricated for Organic Solvent Nanofiltration (OSN) on two different support membranes. Both support membranes, PAN and crosslinked Ultem 1000, displayed pore sizes within the range of 20–25 nm as characterised by gas liquid porometry. PIM layers of < 500 nm thickness were formed from dip coating on a roll-to-roll pilot line. The resultant composite membranes exhibited typical MWCOs in the region of 500–800 g mol −1 . The quality of coating obtained on the crosslinked Ultem 1000 support membrane was consistently higher for all three PIMs than that obtained on the PAN membrane. The PIM composite membranes coated on to crosslinked Ultem 1000 were stable in a wider range of solvents than those on the PAN support. OSN testing in a model system with isomeric alkane solutes verified that manipulated changes to the molecular architecture of the polymer backbone resulted in a higher separation factor between straight and branched alkane isomers. [ABSTRACT FROM AUTHOR]

Ideal adsorbents are featured by both high adsorption capacity and high adsorption rate. Current adsorptive membranes enjoy good mass transfer performance but have limited sorption capacity. Microporous organic polymer has superiorities of small pore size and high surface area which is conductive to high adsorption capacity, but usually suffers from high mass transfer resistance. In this work, the polymer of intrinsic microporosity PIM-1 was fabricated into microfiber membranes by electrospinning for carbendazim and phenol adsorption. The PIM-1 and its electrospun membranes were characterized by 1 H NMR, GPC, ATR-FTIR, FESEM, TG and BET measurements. The electrospun PIM-1 membrane was demonstrated to have hierarchical porous structure with high surface area. The equilibrium adsorption capacity for carbendazim and phenol was 0.084 mmol/g and 0.804 mmol/g, respectively. The adsorption isotherm fits well with Langmuir model and the adsorption kinetic can be described by film diffusion and chemical reaction model. The membrane can retain 95% of its initial capacity after cycling 10 times. Both the sorption capacity and kinetic coefficients are high when comparing with other sorbents for either carbendazim or phenol, demonstrating that the electrospun PIM-1 is a good adsorbent. [ABSTRACT FROM AUTHOR]

Polymers of intrinsic microporosity (PIMs) are among the most promising candidates for the development of novel polymeric gas separation membranes for processes such as carbon capture and storage, natural gas treatment and biogas upgrading. As one of the approaches to optimize their performance, PIMs are functionalized by CO 2 -philic groups to improve the CO 2 separation by the enhancement of specific noncovalent interactions. In this work, we show the preparation of amine-PIM from the archetypal PIM-1, using borane dimethyl sulphide complexes in order to control the degree of conversion. The PIM-1 to amine-PIM-1 conversion was characterized by ATR-IR and NMR analysis. The influence of the amine moiety on the gas transport behaviour was investigated by two complementary techniques: gas permeation measurements by the time lag method and analysis of the sorption kinetics and the equilibrium sorption isotherms by the gravimetric method. Both techniques show that permeability decreases with increasing degree of conversion. The trends in the indirectly calculated solubility confirm those of direct analysis, although quantitative comparison of the two shows fundamental differences. A pressure and temperature study on a fully converted sample indicates that the solution-diffusion model should be expressed in concentration dependent transport parameters to be correct. The experimental work was supported by quantum mechanics studies and by molecular dynamics simulations to confirm the selective non-covalent interaction of CO 2 with the amino groups. [ABSTRACT FROM AUTHOR]

A linear ladder polymer having a high molecular weight ( M n  > 13,000) and reasonable molecular weight distribution ( M w / M n  = 4.4) is successfully prepared by the solution polycondensation of 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI) with decafluorobiphenyl (DFBP) under reaction conditions that are determined using the model reaction of catechol (CC) with DFBP. Further, we observe an undesired intermolecular reaction of the condensed intermediate (CC*-DFBP) with another molecule of DFBP in the model reaction. Thus, polymerization is conducted in two steps under dilute conditions (0.17 mol/L) to suppress the formation of undesired byproducts. Finally, we successfully obtain an approximately linearly connected desired polymer in a good yield (ca. 80%). This controlled linear polymer has better thermal stability (glass transition ( T g ) = 125 °C, 5 wt% loss temperature ( T d5 ) = 490 °C, N 2 ) than the related uncontrolled branched gel polymer. [ABSTRACT FROM AUTHOR]

This work reports on the preparation and gas transport performance of mixed matrix membranes (MMMs) based on the polymer of intrinsic microporosity (PIM-1) and potassium dodecahydrododecaborate (K2B12H12) as inorganic particles (IPs). The effect of IP loading on the gas separation performance of these MMMs was investigated by varying the IP content (2.5, 5, 10 and 20 wt %) in a PIM-1 polymer matrix. The derived MMMs were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), single gas permeation tests and sorption measurement. The PIM1/K2B12H12 MMMs show good dispersion of the IPs (from 2.5 to 10 wt %) in the polymer matrix. The gas permeability of PIM1/K2B12H12 MMMs increases as the loading of IPs increases (up to 10 wt %) without sacrificing permselectivity. The sorption isotherm in PIM-1 and PIM1/K2B12H12 MMMs demonstrate typical dual-mode sorption behaviors for the gases CO2 and CH4. [ABSTRACT FROM AUTHOR]

The synthesis of three novel aromatic polyimides (PIs) containing spiro units is described. These PIs are soluble at room temperature in most common organic solvents, facilitating their processability. Additionally, they are highly thermally stable, with thermal decomposition temperatures (T d10% ) over 500 °C, and had moderately high T g values between 230 and 265 °C. Robust self-standing thin films were prepared from these polyimides, via the solution casting method, which were suitable for gas transport measurements. The relatively low permeability and selectivity of these PIs, as compared to Polymers of Intrinsic Microporosity (PIMs) that also contain spirocyclic structures, demonstrate the importance of restricting rotation within the polymer chain, which is a key structural feature of the PIMs. [ABSTRACT FROM AUTHOR]

Atomistic simulations were performed to investigate pure- and mixed-gas CO 2 /CH 4 separation properties of a ladder polymer of intrinsic microporosity, PIM-Trip-TB. Despite expected intra-chain rigidity of the polymer, previous experimental reports observed significant loss in CO 2 /CH 4 perm-selectivity under high-pressure mixed-gas conditions. In this work, all-atomistic simulations were applied to accurately predict density, gas uptakes and gas diffusion properties of PIM-Trip-TB. Competitive sorption favoring CO 2 over CH 4 was apparent in mixed-gas sorption simulations, as previously demonstrated by experimental studies from our group. This effect resulted in enhanced mixed-gas CO 2 /CH 4 solubility selectivity. However, this increase did not translate to increased mixed-gas perm-selectivity because a significant increase in CH 4 permeability was observed by co-permeation of CO 2 relative to the pure-gas value. Back-calculated diffusion coefficients indicated very low CO 2 /CH 4 diffusion selectivity under mixed-gas conditions, eliminating any gain from competitive sorption. Structural analysis confirmed intact intra-chain rigidity of the polymer; on the other hand, a significant increase in fractional free volume (FFV) and shift to larger pores in the pore size distribution was revealed by our simulations which may be attributed to polymer dilation due a reduction in inter-chain packing. [Display omitted] • Pure- and mixed-gas CO 2 /CH 4 transport properties of PIM-Trip-TB were modeled accurately. • The effects of competitive sorption and co-permeation under mixed-gas conditions were analyzed. • PIM-Trip-TB preserved its initial intra-chain rigidity under mixed-gas conditions. • CO 2 -induced reduction of inter-chain packing led to loss in mixed-gas CO 2 /CH 4 diffusion- and perm-selectivity. [ABSTRACT FROM AUTHOR]

Polymers of intrinsic microporosity (PIMs) are a promising membrane material for gas separation, because of their high free volume and micro-cavity size distribution. This is countered by PIMs-based membranes being highly susceptible to physical aging, which dramatically reduces their permselectivity over extended periods of time. Supercritical carbon dioxide is known to plasticize and partially solubilise polymers, altering the underlying membrane morphology, and hence impacting the gas separation properties. This investigation reports on the change in PIM-1 membranes after being exposed to supercritical CO2 for two- and eight-hour intervals, followed by two depressurization protocols, a rapid depressurization and a slow depressurization. The exposure times enables the impact contact time with supercritical CO2 has on the membrane morphology to be investigated, as well as the subsequent depressurization event. The density of the post supercritical CO2 exposed membranes, irrespective of exposure time and depressurization, were greater than the untreated membrane. This indicated that supercritical CO2 had solubilised the polymer chain, enabling PIM-1 to rearrange and contract the free volume micro-cavities present. As a consequence, the permeabilities of He, CH4, O2 and CO2 were all reduced for the supercritical CO2-treated membranes compared to the original membrane, while N2 permeability remained unchanged. Importantly, the physical aging properties of the supercritical CO2-treated membranes altered, with only minor reductions in N2, CH4 and O2 permeabilities observed over extended periods of time. In contrast, He and CO2 permeabilities experienced similar physical aging in the supercritical treated membranes to that of the original membrane. This was interpreted as the supercritical CO2 treatment enabling micro-cavity contraction to favour the smaller CO2 molecule, due to size exclusion of the larger N2, CH4 and O2 molecules. Therefore, physical aging of the treated membranes only had minor impact on N2, CH4 and O2 permeability; while the smaller He and CO2 gases experience greater permeability loss. This result implies that supercritical CO2 exposure has potential to limit physical aging performance loss in PIM-1 based membranes for O2/N2 separation.

Polymers of intrinsic microporosity (PIMs) have promising gas adsorption properties for potential applications such as incorporation into high-pressure hydrogen storage tanks in an effort to increase the storage capacity or decrease the operating pressure. Such applications require detailed mechanical characterisation and determination of the structure-properties relationships to enable optimisation of the interface between the polymer and the tank. In this study, we show that Atomic Force Microscopy (AFM) nanoindentation can be used to determine the elastic modulus of cast PIM-1 films and that this property is depth-dependent. Average values of elastic modulus obtained experimentally were 1.87 GPa and are compared with elastic tensile modulus and storage tensile modulus obtained in previous studies. In addition, Scanning Electron Microscopy (SEM) and AFM imaging was performed to investigate the surface structure of the cast PIM-1 film, which has been shown to be highly granular. [ABSTRACT FROM AUTHOR]

Membranes that enable the recovery of organic compounds from dilute aqueous solution are desired for applications such as biobutanol production. The polymer of intrinsic microporosity PIM-1 shows promise for organophilic separations and here it is incorporated into thin film composite (TFC) membranes in order to increase the flux of permeate. Asymmetric polyvinylidene fluoride (PVDF) supports were prepared with pore sizes at the surface in the size range 25–55 nm and fractional surface porosities in the range 0.38–0.69, as determined by atomic force microscopy (AFM). The addition of phosphoric acid to the PVDF dope solution helped to control the pore size and porosity. Supports were coated with PIM-1 to form TFC membranes with active layer thicknesses in the range 1.0–2.9 µm. Membranes were tested for the pervaporation of a 1-butanol/water mixture (5 wt%). At 65 °C, values of total flux up to 9 kg m −2 h −1 were obtained, with separation factors up to 18.5 and values of pervaporation separation index (PSI) up to 112 kg m −2 h −1 . [ABSTRACT FROM AUTHOR]