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Dibenzomethanopentacene (DBMP) is shown to be a useful structural component for making Polymers of Intrinsic Microporosity (PIMs) with promise for making efficient membranes for gas separations. DBMP-based monomers for PIMs are readily prepared using a Diels-Alder reaction between 2,3-dimethoxyanthracene and norbornadiene as the key synthetic step. Compared to date for the archetypal PIM-1, the incorporation of DBMP simultaneously enhances both gas permeability and the ideal selectivity for one gas over another. Hence, both ideal and mixed gas permeability data for DBMP-rich co-polymers and an amidoxime modified PIM are close to the current Robeson upper bounds, which define the state-of-the-art for the trade-off between permeability and selectivity, for several important gas pairs. Furthermore, long-term studies (over ~3 years) reveal that the reduction in gas permeabilities on ageing is less for DBMP-containing PIMs relative to that for other high performing PIMs, which is an attractive property for the fabrication of membranes for efficient gas separations.

Low-temperature electrolysis by using polymer electrolyte membranes (PEM) can play animportant role in hydrogen energy transition. This work presents a study on the performance of aproton exchange membrane in the water electrolysis process at room temperature and atmosphericpressure. In the perspective of applications that need a device with small volume and low weight, aminiaturized electrolysis cell with a 36 cm2active area of PEM over a total surface area of 76 cm2of thedevice was used. H2and O2production rates, electrical power, energy efficiency, Faradaic efficiencyand polarization curves were determined for all experiments. The effects of different parameters suchas clamping pressure and materials of the electrodes on polarization phenomena were studied. ThePEM used was a catalyst-coated membrane (Ir-Pt-Nafion(TM)117 CCM). The maximum H2productionwas about 0.02 g min-1with a current density of 1.1 A cm-2and a current power about 280 W.Clamping pressure and the type of electrode materials strongly influence the activation and ohmicpolarization phenomena. High clamping pressure and electrodes in titanium compared to carbonelectrodes improve the cell performance, and this results in lower ohmic and activation resistances (PDF) Green H2 Production by Water Electrolysis Using Cation Exchange Membrane: Insights on Activation and Ohmic Polarization Phenomena.

Low-temperature electrolysis by using polymer electrolyte membranes (PEM) can play an important role in hydrogen energy transition. This work presents a study on the performance of a proton exchange membrane in the water electrolysis process at room temperature and atmospheric pressure. In the perspective of applications that need a device with small volume and low weight, a miniaturized electrolysis cell with a 36 cm2 active area of PEM over a total surface area of 76 cm2 of the device was used. H2 and O2 production rates, electrical power, energy efficiency, Faradaic efficiency and polarization curves were determined for all experiments. The effects of different parameters such as clamping pressure and materials of the electrodes on polarization phenomena were studied. The PEM used was a catalyst-coated membrane (Ir-Pt-Nafion™ 117 CCM). The maximum H2 production was about 0.02 g min−1 with a current density of 1.1 A cm−2 and a current power about 280 W. Clamping pressure and the type of electrode materials strongly influence the activation and ohmic polarization phenomena. High clamping pressure and electrodes in titanium compared to carbon electrodes improve the cell performance, and this results in lower ohmic and activation resistances.

Polymer-based membranes can be used for energy efficient gas separations. Successful exploitation of new materials requires accurate knowledge of the transport properties of all gases of interest. An open source database of such data is of significant benefit to the research community. The Membrane Society of Australasia (https://membrane-australasia.org/) hosts a database for experimentally measured and reported polymer gas permeabilities. However, the database is incomplete, limiting its potential use as a research tool. Here, missing values in the database were filled using machine learning (ML). The ML model was validated against gas permeability measurements that were not recorded in the database. Through imputing the missing data, it is possible to re-analyse historical polymers and look for potential “missed” candidates with promising gas selectivity. In addition, for systems with limited experimental data, ML using sparse features was performed, and we suggest that once the permeability of CO2 and/or O2 for a polymer has been measured, most other gas permeabilities and selectivities, including those for CO2/CH4 and CO2/N2, can be quantitatively estimated. This early insight into the gas permeability of a new system can be used at an initial stage of experimental measurements to rapidly identify polymer membranes worth further investigation.

Polymers of intrinsic microporosity (PIMs), such as the archetypal spirobisindane-based PIM-1, are among the most promising new materials for making gas separation membranes with high permeance for potential use in high-throughput applications. Here it is shown that ultrapermeable PIMs can be prepared by fusing rigid and bulky triptycene (Trip) to the spirobisindane (SBI) unit. PIM-SBI-Trip and its copolymer with PIM-1 (PIM-1/SBI-Trip) are both ultrapermeable after methanol treatment (PCO2 > 20 000 Barrer). Old films, although less permeable, are more selective and therefore provide data that are close to the recently redefined Robeson upper bounds for the important CO2/CH4, CO2/N2, and O2/N2 gas pairs. Temperature-dependent permeation measurements and analysis of the entropic and energetic contributions of the gas transport parameters show that the enhanced performance of these polymers is governed by strong size-sieving character, mainly due to the energetic term of the diffusivity, and related to their high rigidity. Both polymers show a relatively weak pressure-dependence in mixed gas permeability experiments up to 6 bar, suggesting a potential use for CO2 capture from flue gas or for the upgrading of biogas.

This manuscript describes the gas separation performance of PIM-2, a partially fluorinated linear copolymer synthesized from 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethylspirobisindane (TTSBI) and decafluorobiphenyl (DFBP). As one of the early members of the family of polymers of intrinsic microporosity, it had never been tested as a gas separation membrane because of insufficient mechanical resistance. This has been solved only recently, allowing the preparation of robust self-standing films. Molecular modelling studies demonstrated a high fractional free volume (34%) and an elevated surface area (642 m2 g-1), and the latter is in good agreement with experimental BET results. Pure gas permeabilities measured on a fixed-volume time-lag instrument at 1 bar compare well with the results of mixed separation tests on a variable volume setup from 1-6 bar(a). Molecular modelling and independent sorption measurements on a gravimetric sorption balance both show strong dual-mode sorption behaviour, especially for CO2 and to a lesser extent for CH4. Temperature-dependent pure gas permeation measurements show typical Arrhenius behaviour, with a clear increase in the activation energy for diffusion with the increasing molecular size of the gas, indicating high size-selectivity. This is in agreement with the highly rigid PIM structure, determined by AFM force spectroscopy measurements. The dual-mode behaviour results in a moderate pressure dependence of the CO2 permeability and the CO2/N2 and CO2/CH4 selectivity, all slightly decreasing with increasing pressure. The presence of humidity in the gas stream has a remarkable small effect on the membrane performance, which is probably due to the high fluorine content and the consequently low water vapour solubility in the polymer, as confirmed by gravimetric sorption measurements. The manuscript describes an extensive study on the structure-property relationships in PIM-2. © 2019 Elsevier B.V. European Commission, EC Grantová Agentura Ceské Republiky, GA Ä?R: 18-05484S --Research on biogas upgrading presented in this work was supported by EU structural funding in the frame of Operational Programme Research, Development and Education, project No. CZ.02.1.01./0.0/0.0/17_049/0008419 “COOPERATION”. This work was further supported by the CNR-CAS bilateral agreement 2016–2018 “Innovative polymeric membranes for pervaporation and advanced gas and vapour separations” and by the Czech Science Foundation (grant no. 18-05484S ). Appendix A

The relationship, during physical aging, between the transport properties and Young’s modulus for films of polymers of intrinsic microporosity (PIM) was investigated using pure gas permeability and atomic force microscopy (AFM) in force spectroscopy mode. Excellent agreement of Young’s modulus measured for the archetypal PIM-1 with values obtained by other techniques in the literature, confirms the suitability of AFM force spectroscopy for the rapid and convenient assessment of mechanical properties. Results from different polymers including PIM-1 and five ultrapermeable benzotriptycene-based PIMs provide direct evidence that size selectivity is strongly correlated to Young’s modulus. In addition, film samples of one representative PIM (PIM-DTFM-BTrip) were subjected to both normal physical aging and to accelerated aging by thermal conditioning under vacuum for comparison. Accelerated aging resulted in a similar decrease in permeability and increase in Young’s modulus as normal aging, however, significant differences suggest that thermally induced accelerated aging occurs throughout the bulk of the polymer film whereas normal aging occurs predominantly at the surface of the film. For all PIMs, the increased in film rigidity upon aging led to an increase in gas size selectivity.

A detailed analysis of the basic transport parameters of two triptycene-based polymers of intrinsic microporosity (PIMs), the ultrapermeable PIM-TMN-Trip and the more selective PIM-BTrip, as a function of temperature from 25 to 55 degrees C, is reported. For both PIMs, high permeability is based on very high diffusion and solubility coefficients. The contribution of these two factors on the overall permeability is affected by the temperature and depends on the penetrant dimensions. Energetic parameters of permeability, diffusivity, and solubility are calculated using Arrhenius-van't Hoff equations and compared with those of the archetypal PIM-1 and the ultrapermeable, but poorly selective poly(trimethylsilylpropyne). This considers, for the first time, the role of entropic and energetic selectivities in the diffusion process through highly rigid PIMs. This analysis demonstrates that how energetic selectivity dominates the gas-transport properties of the highly rigid triptycene PIMs and enhances the strong size-sieving character of these ultrapermeable polymers.

The growing interest towards the hydrogen utilization as energy carrier placed a high demand on hydrogen permeable membranes as compact devices for hydrogen separation and purification. Many studies in this scientific field demonstrated that the composite Pd-based membranes are particularly effective for the aforementioned purposes, particularly if compared to the utilization of self-supported Pd-based membranes for their high cost and mechanical limitations. As a case study, a composite membrane based on a thin Pd-Au (8 μm of metallic layer and 12 wt% of Au) supported on α-Al2O3 substrate was produced by electroless plating deposition. Permeation tests were performed with pure gases (H2, N2, CO2, CH4) by varying the temperature between 300 °C and 400 °C and the feed pressure from 150 to 350 kPa. The exponential factor (n-value) in the equation describing the relationship between the hydrogen flux permeating through the membrane and its driving force was analyzed as a function of temperature and pressure variation. An apparent activation energy of 11 kJ/mol has been reached and it is comparable to other data present in the open literature. A H2/N2 ideal selectivity of around 500 was reached at 400 °C and 50 kPa of transmembrane pressure and it remained stable up to 600 h under operation. The presence of defects on the metallic layer has affected the membrane performance in terms of H2 perm-selectivity as testified by the post-mortem analysis on the exhausted membrane.

Polymers of Intrinsic Microporosity (PIMs) combine the desirable processability of polymers, with a significant degree of microporosity generated from the inefficient packing of their rigid and contorted macromolecular structures. They are attracting attention for a number of industrial gas separation applications, such as oxygen or nitrogen separation from air (i.e. separation O2/N2) or natural gas treatment and biogas upgrading (i.e. separation CO2/CH4). However, a further enhancement of the polymer transport properties is desirable to be cost effective in comparison with the traditional separation technology, currently applied for CO2 capture or removal. In this work, we report a series of benzotriptycene-based PIMs showing outstanding CO2/CH4 and CO2/N2 permselectivity properties [1], due to the inefficient packing of their 2D polymeric chains which results in large interconnected pores that enhance gas permeability. These benzotriptycene-based PIMs demonstrate ultrapermeability (PCO2>20000 Barrer) and interesting selectivity, and their combination allows the introduction of a new upper bound to define the current state-of-the-art for CO2 membrane separation processes (Figure 1). Their gas transport properties will be discussed in terms of permeability, diffusivity and solubility on freshly methanol treated and aged samples. The effect of the temperature on the transport properties will be also discussed. Particular attention will be paid to the relative contribution of diffusivity coefficients with the analysis of the size-selectivity in terms of entropic and energetic selectivity [2], and as a function of the effective diameter of the penetrant gas [3]. The latter analysis demonstrates that the diffusivity of light gases through PIMs shows that smaller H2 and He gas molecules have a transport mechanism that is similar to that of porous materials, whereas larger gas molecules, CH4, N2, O2 and CO2, show activated transport similar to that of conventional dense polymers. A typical and defining feature of PIMs, which differentiates their properties from other high free volume polymers, glassy polymers and rubbers, is the change in slope of the plot of the diffusion coefficient as a function of the gas diameter, with a stronger size-selective trend for the larger gas molecules than for He and H2. References: [1]B. Comesaña-Gándara, J. Chen, C.G. Bezzu, M. Carta, I. Rose, M.-C. Ferrari, E. Esposito, A. Fuoco, J.C. Jansen, N.B. McKeown, Redefining the Robeson upper bounds for CO 2 /CH 4 and CO 2 /N 2 separations using a series of ultrapermeable benzotriptycene-based polymers of intrinsic microporosity, Energy Environ. Sci. (2019). doi:10.1039/C9EE01384A. [2]A. Fuoco, B. Comesaña-Gándara, M. Longo, E. Esposito, M. Monteleone, I. Rose, C.G. Bezzu, M. Carta, N.B. McKeown, J.C. Jansen, Temperature Dependence of Gas Permeation and Diffusion in Triptycene-Based Ultrapermeable Polymers of Intrinsic Microporosity, ACS Appl. Mater. Interfaces. 10 (2018) 36475-36482. doi:10.1021/acsami.8b13634. [3]A. Fuoco, C. Rizzuto, E. Tocci, M. Monteleone, E. Esposito, P.M. Budd, M. Carta, B. Comesaña-Gándara, N.B. McKeown, J.C. Jansen, The origin of size-selective gas transport through polymers of intrinsic microporosity, J. Mater. Chem. A. 7 (2019) 20121-20126. doi:10.1039/C9TA07159H.

This paper presents Atomic Force Microscopy (AFM) as a powerful alternative to the more commonly used tensile tests for the analysis of the mechanical properties of polymeric membranes. The Young's modulus measurements by the traditional tensile tests were compared with AFM operated in Force Spectroscopy mode. AFM measurements were carried out with nanometric and micrometric tips on dense membranes of neat Pebax®1657 and on mixed matrix membranes of Pebax®1657 with different concentrations of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]. The use of a nanometric AFM tip enables the determination of the local Young's modulus of the individual domains of the microphase-separated block-copolymer, while a larger tip gives average values of the bulk polymer. We found excellent correlation between the data obtained with common tensile tests and those obtained in compression by AFM with the micrometric tip, with important additional information on morphological features, when using the nanometric tip. This offers good perspectives for the analysis of samples where traditional tensile tests cannot be used, for instance composite membranes or particularly small samples.