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Nickel nanoparticle electrodeposition is studied on flat glassy carbon (GC) or on nitrogen‐doped reduced graphene oxide (rGO‐N) substrates. The effects of a very thin (nominally 16 nm) layer polymer of intrinsic microporosity (PIM‐1) are investigated (i) on enhancing nickel nanoparticle nucleation and growth during electrodeposition and (ii) on enhancing hydrogen evolution electrocatalysis. Beneficial effects are tentatively assigned to PIM‐1 suppressing blocking effects from interfacial hydrogen bubble formation. Exploratory data suggest that in aqueous 0.5 M NaCl solution (artificial seawater) nickel nanoparticles grown into a thin film of PIM‐1 could be a viable electrocatalyst with an onset of hydrogen evolution only slightly negative compared to that observed for platinum nanoparticles. [ABSTRACT FROM AUTHOR]

In this work, a new polymeric binder (polymer of intrinsic microporosity, PIM‐1) has been investigated and discussed to prepare and characterize composite materials for the cathodic oxygen reduction reaction. The new binder is a polymer of intrinsic microporosity, a family of organic compounds with molecularly rigid (glassy) structure, good mechanical and chemical stability. Their influence on the electrocatalytic behaviour of a commercial electrocatalyst during the oxygen reduction reaction in acidic and alkaline media has been investigated, discussed and compared to the behaviour of common cationic and anionic polymer binders, using rotating disk electrode (RDE) techniques. Polymers of intrinsic microporosity perform similarly well, and sometimes better (due to rigidity and gas permeation) when compared to commercial binders. Thus, herein, we showed that PIMs do represent a very promising and versatile alternative as binders in electrocatalysis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) is an emerging membrane separation technology, which urgently requires robust, easily processed, OSN membranes possessing high permeance and small solutes‐selectivity to facilitate enhanced industrial uptake. Herein, we describe the use of two 2,2′‐biphenol (BIPOL) derivatives to fabricate hyper‐crosslinked, microporous polymer nanofilms through IP. Ultra‐thin, defect‐free polyesteramide/polyester nanofilms (≈5 nm) could be obtained readily due to the relatively large molecular size and ionized nature of the BIPOL monomers retarding the rate of the IP. The enhanced microporosity arises from the hyper‐crosslinked network structure and monomer rigidity. Specifically, the amino‐BIPOL/PAN membrane exhibits extraordinary permselectivity performances with molecular weight cut‐off as low as 233 Da and MeOH permeance of ≈13 LMH/bar. Precise separation of small dye mixtures with similar M.W. based on both their charge and molecular size are achieved. [ABSTRACT FROM AUTHOR]

Advances in materials science have accelerated the development of diagnostic tools with the last decade witnessing the development of enzyme-free sensors, owing to the improved stability, low cost and simple fabrication of component materials. However, the specificity of non-enzymatic sensors for certain analytes still represents a challenging task, for example the determination of cholesterol level in blood is vital due to its medical relevance. In this work, a reagent displacement assay for cholesterol sensing in serum samples was developed. It is based on coating of a glassy carbon electrode with a polymer of intrinsic microporosity (PIM) that forms a host-guest complex with methylene blue (MB). In the presence of cholesterol, the MB electroactive probe was displaced due to the stronger association of cholesterol guest to the PIM host. The decrease in the oxidative current was proportional to the cholesterol concentration achieving a detection limit of approximately 0.1 nM. Moreover, to further assist the experimental studies, comprehensive theoretical calculations are also performed by using density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The polymer of intrinsic microporosity PIM‐1 is employed to disperse and deposit a Pt@titanate nanosheet photocatalyst film. The resulting microporous films allow electrolyte and oxygen permeation to give conventional oxygen reduction voltammetric responses on glassy carbon or on platinum disk electrodes in the dark. Preliminary data are presented showing that with pulsed light from a blue LED (385 nm) oxygen reduction at the electrode is effectively "switched off". A mechanism is tentatively assigned as photocatalytic depletion of oxygen near the electrode. Photoelectrochemical current responses are observed in aqueous NaOH, NaCl, Na2HPO4 and shown to be light intensity and oxygen concentration dependent. Electroanalytical applications are suggested. [ABSTRACT FROM AUTHOR]

Protonation of the molecularly rigid polymer of intrinsic microporosity PIM-EA-TB can be coupled to immobilisation of Fe(CN)63−/4− (as well as immobilisation of Prussian blue) into 1–2 nm diameter channels. The resulting films provide redox-active coatings on glassy carbon electrodes. Uptake, transport, and retention of Fe(CN)63−/4− in the microporous polymer are strongly pH dependent requiring protonation of the PIM-EA-TB (pKA ≈ 4). Both Fe(CN)64− and Fe(CN)63− can be immobilised, but Fe(CN)64− appears to bind tighter to the polymer backbone presumably via bridging protons. Loss of Fe(CN)63−/4− by leaching into the aqueous solution phase becomes significant only at pH > 9 and is likely to be associated with hydroxide anions directly entering the microporous structure to combine with protons. This and the interaction of Fe(CN)63−/4− and protons within the molecularly rigid PIM-EA-TB host are suggested to be responsible for retention and relatively slow leaching processes. Electrocatalysis with immobilised Fe(CN)63−/4− is demonstrated for the oxidation of ascorbic acid. [ABSTRACT FROM AUTHOR]

Hybrid electrodes with improved O2 tolerance and capability of CO2 conversion into liquid products in the presence of O2 are presented. Aniline molecules are introduced into the pore structure of a polymer of intrinsic microporosity to expand its gas separation functionality beyond pure physical sieving. The chemical interaction between the acidic CO2 molecule and the basic amino group of aniline renders enhanced CO2 separation from O2. Loaded with a cobalt phthalocyanine‐based cathode catalyst, the hybrid electrode achieves a CO Faradaic efficiency of 71 % with 10 % O2 in the CO2 feed gas. The electrode can still produce CO at an O2/CO2 ratio as high as 9:1. Switching to a Sn‐based catalyst, for the first time O2‐tolerant CO2 electroreduction to liquid products is realized, generating formate with nearly 100 % selectivity and a current density of 56.7 mA cm−2 in the presence of 5 % O2. [ABSTRACT FROM AUTHOR]

The performance and safety of lithium (Li) metal batteries can be compromised owing to the formation of Li dendrites. Here, the use of a polymer of intrinsic microporosity (PIM) is reported as a feasible and robust interfacial layer that inhibits dendrite growth. The PIM demonstrates excellent film‐forming ability, electrochemical stability, strong adhesion to a copper metal electrode, and outstanding mechanical flexibility so that it relieves the stress of structural changes produced by reversible lithiation. Importantly, the porous structure of the PIM, which guides Li flux to obtain uniform deposition, and its strong mechanical strength combine to suppress dendrite growth. Hence, the electrochemical performance of the anode is significantly enhanced, promising excellent performance and extended cycle lifetime for Li metal batteries. [ABSTRACT FROM AUTHOR]

Polymers of intrinsic microporosity (PIMs) as molecularly rigid polymers have emerged as a new class of gas‐permeable glassy materials. They offer excellent processability and a range of potential applications also in electrochemical processes. Particularly interesting is the ability of some PIM films to remain gas‐permeable/binding even in the presence of (aqueous) liquid electrolyte to give triphasic interfacial reactivity. Gaseous reagents or products (such as hydrogen or oxygen) are bound probably into hydrophobic regions in the wet PIM film to avoid macroscopic bubble formation and to enhance both the surface reactivity and the apparent activity of the gas solute close to the electrode/catalyst surface. The photoelectrochemical formation of hydrogen gas close to a platinum electrode is enhanced by PIM‐1, which is presented as an example of energy harvesting through molecular H2 "energy carrier" transport. [ABSTRACT FROM AUTHOR]

A film of the polymer of intrinsic microporosity PIM‐7 is coated onto a glassy carbon electrode and the resulting effects on electron transfer reactions are studied for three different types of processes: (i) aqueous solution based, (ii) solid state surface immobilised, and (iii) electrocatalytic processes on electrodeposited palladium. The effects on reactivity for hydroquinone oxidation in aqueous phosphate buffer are shown to be linked to microporosity causing a slightly lower rate of mass transport without detrimental effects on electron transfer and reaction kinetics. Next, water‐insoluble microcrystalline anthraquinone is immobilised directly into the PIM‐7 film and shown to give a chemically reversible reduction process, which is enhanced in the presence of PIM‐7, when compared to the case of anthraquinone immobilised directly onto bare glassy carbon. Electrodeposition of a film of nano‐palladium is demonstrated to give catalytically active electrodes for the reduction/oxidation of protons/hydrogen, the reduction of oxygen, and for the oxidation of formic acid and methanol. With the PIM‐7 film applied onto palladium, a mechanical stabilisation effect occurs. In addition, both the hydrogen insertion and the hydrogen evolution reactions as well as formic acid oxidation are enhanced. Effects are discussed in terms of PIM‐7 beneficially affecting the interfacial reaction under triphasic conditions. The microporous polymer acts as an interfacial "gas management" layer. [ABSTRACT FROM AUTHOR]

The one-step vacuum carbonization synthesis of a platinum nano-catalyst embedded in a microporous heterocarbon (Pt@cPIM) is demonstrated. A nitrogen-rich polymer of an intrinsic microporosity (PIM) precursor is impregnated with PtCl62- to give (after vacuum carbonization at 700 °C) a nitrogen-containing heterocarbon with embedded Pt nanoparticles of typically 1-4 nm diameter (with some particles up to 20 nm diameter). The Brunauer-Emmett-Teller (BET) surface area of this hybrid material is 518 m2 g-1 (with a cumulative pore volume of 1.1 cm3 g-1) consistent with the surface area of the corresponding platinum-free heterocarbon. In electrochemical experiments, the heterocarbon-embedded nano-platinum is observed as reactive towards hydrogen oxidation, but essentially non-reactive towards bigger molecules during methanol oxidation or during oxygen reduction. Therefore, oxygen reduction under electrochemical conditions is suggested to occur mainly via a 2-electron pathway on the outer carbon shell to give H2O2. Kinetic selectivity is confirmed in exploratory catalysis experiments in the presence of H2 gas (which is oxidized on Pt) and O2 gas (which is reduced on the heterocarbon surface) to result in the direct formation of H2O2. [ABSTRACT FROM AUTHOR]

The use of ultrathin films as selective layers in composite membranes offers significant advantages in gas separation for increasing productivity while reducing the membrane size and energy costs. In this contribution, composite membranes have been obtained by the successive deposition of approximately 1 nm thick monolayers of a polymer of intrinsic microporosity (PIM) on top of dense membranes of the ultra-permeable poly[1-(trimethylsilyl)-1-propyne] (PTMSP). The ultrathin PIM films (30 nm in thickness) demonstrate CO2 permeance up to seven times higher than dense PIM membranes using only 0.04 % of the mass of PIM without a significant decrease in CO2/N2 selectivity. [ABSTRACT FROM AUTHOR]

Ionic diode phenomena occur at asymmetric ionomer | aqueous electrolyte microhole interfaces. Depending on the applied potential, either an 'open' or a 'closed' diode state is observed switching between a high ion flow rate and a low ion flow rate. Physically, the 'open' state is associated mainly with conductivity towards the microhole within the ionomer layer and the 'closed' state is dominated by restricted diffusion-migration access to the microhole interface opposite to the ionomer. In this report we explore a 'heterojunction' based on an asymmetric polymer of intrinsic microporosity (PIM) | Nafion ionomer microhole interface. Improved diode characteristics and current rectification are observed in aqueous NaCl. The effects of creating the PIM | Nafion micro-interface are investigated and suggested to lead to novel sensor architectures. [ABSTRACT FROM AUTHOR]

In contrast to most common electrochemiluminescence (ECL) techniques that require either an additional reagent or continuous pulsing between oxidative and reductive potentials, here a fluorescent polymer of intrinsic microporosity (PIM-1) is shown to exhibit intrinsic ECL without the need for a co-reactant at positive applied potentials and as a function of pH. PIM-1 is known to possess high microporosity (based on its rigid and contorted molecular structure) and excellent fluorescence properties. By depositing a nanoparticulate form of the PIM-1 material onto tin-doped indium oxide, we achieve a hierarchically porous deposit with good sustained ECL activity in aqueous media. The mechanism for this reagentless ECL is suggested to be linked to reactive oxygen species produced at positive potentials and discussed in terms of potential analytical applications. [ABSTRACT FROM AUTHOR]

Efficient reactions between fluorine-functionalised biphenyl and terphenyl derivatives with catechol-functionalised terminal groups provide a route to large, discrete organic molecules of intrinsic microporosity (OMIMs) that provide porous solids solely by their inefficient packing. By altering the size and substituent bulk of the terminal groups, a number of soluble compounds with apparent BET surface areas in excess of 600 m2 g−1 are produced. The efficiency of OMIM structural units for generating microporosity is in the order: propellane>triptycene>hexaphenylbenzene>spirobifluorene>naphthyl=phenyl. The introduction of bulky hydrocarbon substituents significantly enhances microporosity by further reducing packing efficiency. These results are consistent with findings from previously reported packing simulation studies. The introduction of methyl groups at the bridgehead position of triptycene units reduces intrinsic microporosity. This is presumably due to their internal position within the OMIM structure so that they occupy space, but unlike peripheral substituents they do not contribute to the generation of free volume by inefficient packing. [ABSTRACT FROM AUTHOR]

Based on almost 20 years of published research, the structure-property relationships of Polymers of Intrinsic Microporosity (PIMs) are considered. Following an analysis of the structure of the archetypal PIM-1 and how it contributes to its now well-understood properties, the key properties of solubility, thermal properties, gas adsorption and gas permeability are related to the structures of more recently prepared PIMs. In order to deliver their technological potential, it is recommended that further synthetic effort should focus both on broadening the structural diversity of PIMs and providing synthetically accessible variants. [ABSTRACT FROM AUTHOR]

A highly rigid amine-based polymer of intrinsic microporosity (PIM), prepared by a polymerization reaction involving the formation of Tröger's base, is demonstrated to act as an ionic diode with electrolyte-dependent bistable switchable states. [ABSTRACT FROM AUTHOR]

The enzymeless glucose oxidation process readily occurs on nano-gold electrocatalyst at pH 7, but it is highly susceptible to poisoning (competitive binding), for example from protein or chloride. Is it shown here that gold nanoparticle catalyst can be protected against poisoning by a polymer of intrinsic microporosity (PIM-EA-TB with BET surface area 1027 m2 g−1). This PIM material when protonated, achieves a triple catalyst protection effect by (i) size selective repulsion of larger protein molecules (albumins) and (ii) membrane ion selection effects, and (iii) membrane ion activity effects. PIM materials allow 'environmental control' to be introduced in electrocatalytic processes. [ABSTRACT FROM AUTHOR]

The microscopic diffusion and the low frequency density of states (VDOS) of PIM-EA-TB(CH3) are investigated by inelastic and quasi-elastic neutron scattering where also the demethylated counterpart of PIM-EA-TB(H2) is considered. These intrinsic microporous polymers are characterized by large BET surface area values of several hundred m2/g and pore sizes between 0.5 and 2 nm. Detailed comparison is made to the archetype of polymers of intrinsic microporosity, PIM-1, and polynorbornenes also bearing a microporosity. Due to the wavelength of neutrons, the diffusion and vibrations can be addressed on microscopic length and time scales. From the inelastic neutron scattering experiments the low frequency density of states (VDOS) is estimated which shows excess contributions to the Debye-type VDOS known as Boson peak. It was found that the maximum frequency of the Boson peak decreases with increasing microporosity characterized by the BET surface area. However, besides the BET surface area, additional factors such as the backbone stiffness govern the maximum frequency of the Boson peak. Further the mean squared displacement related to microscopic motions was estimated from elastic fixed window scans. At temperatures above 175 K, the mean squared displacement PIM-EA-TB(CH3) is higher than that for the demethylated counterpart PIM-EA-TB(H2). The additional contribution found for PIM-EA-TB(CH3) is ascribed to the rotation of the methyl group in this polymer because the only difference between the two structures is that PIM-EA-TB(CH3) has methyl groups where PIM-EA-TB(H2) has none. A detailed comparison of the molecular dynamics is also made to that of PIM-1 and the microporous polynorbornene PTCNSi1. The manuscript focuses on the importance of vibrations and the localized molecular mobility characterized by the microscopic diffusion on the gas transport in polymeric separation membranes. In the frame of the random gate model localized fluctuations can open or close bottlenecks between pores to enable the diffusion of gas molecules. [ABSTRACT FROM AUTHOR]

This paper focuses on polymers that demonstrate microporosity without possessing a network of covalent bonds--the so-called polymers of intrinsic microporosity (PIM). PIMs combine solution processability and microporosity with structural diversity and have proven utility for making membranes and sensors. After a historical account of the development of PIMs, their synthesis is described along with a comprehensive review of the PIMs that have been prepared to date. The important methods of characterising intrinsic microporosity, such as gas absorption, are outlined and structure-property relationships explained. Finally, the applications of PIMs as sensors and membranes for gas and vapour separations, organic nanofiltration, and pervaporation are described. [ABSTRACT FROM AUTHOR]

This study reports for the first time the preparation of an electrospun microfibrous mat of PIM-EA-TB. The electrospinning was carried out using a chloroform/n-Propyl-lactate (n-PL) binary solvent system with different chloroform/nPL ratios, in order to control the morphology of the microfibres. With pure chloroform, porous and dumbbell shape fibres were obtained whereas, with the addition on n-PL, circular and thinner fibres have been produced due to the higher boiling point and the higher conductivity of n-PL. The electrospinning process conditions were investigated to evaluate their impact on the fibres' morphology. These microfibrous mats presented potential to be used as breathable/waterproof materials, with a pore diameter of 11 μm, an air resistance of 25.10−7 m−1 and water breakthrough pressure of 50 mBar. [ABSTRACT FROM AUTHOR]

A novel triptycene-based polymer of intrinsic microporosity (Trip-PIM) displays enhanced surface area (1065 m² g-1) and reversibly adsorbs 1.65% hydrogen by mass at 1 bar/77 K and 2.71% at 10 bar/77 K. [ABSTRACT FROM AUTHOR]

Based on cumulative research from the past two decades, this personal perspective defines the structurally unique features of Polymers of Intrinsic Microporosity (PIMs), which result in a distinct combination of properties, including solution-processability and microporosity, providing organic materials suitable for the fabrication of membranes that perform efficient molecular sieving. Image 1 • Personal reflection on the development of Polymers of Intrinsic Microporosity (PIMs). • Explanation of why PIMs form a distinct class of polymer and microporous material. • Re-definition of PIMs based on their method of synthesis, structure and properties. • Rigidity and sub-nanometre pore size combine to make PIM membranes selective. • Free volume is largely interconnected but only for the transport of small gases. [ABSTRACT FROM AUTHOR]

A detailed comparison of the gas permeability of four Polymers of Intrinsic Microporosity containing Tröger's base (TB-PIMs) is reported. In particular, we present the results of a systematic study of the differences between four related polymers, highlighting the importance of the role of methyl groups positioned at the bridgehead of ethanoanthracene (EA) and triptycene (Trip) components. The PIMs show BET surface areas between 845–1028 m2 g−1 and complete solubility in chloroform, which allowed for the casting of robust films that provided excellent permselectivities for O2/N2, CO2/N2, CO2/CH4 and H2/CH4 gas pairs so that some data surpass the 2008 Robeson upper bounds. Their interesting gas transport properties were mostly ascribed to a combination of high permeability and very strong size-selectivity of the polymers. Time lag measurements and determination of the gas diffusion coefficient of all polymers revealed that physical ageing strongly increased the size-selectivity, making them suitable for the preparation of thin film composite membranes. [ABSTRACT FROM AUTHOR]

Microporous polymer nanosheets with thicknesses in the range 3–5 nm and with high apparent surface area (Brunauer–Emmett–Teller surface area 940 m2 g−1) are formed when the effectively bifunctional (tetrafluoro) monomer used in the preparation of the prototypical polymer of intrinsic microporosity PIM‐1 is replaced with an effectively tetrafunctional (octafluoro) monomer to give a tightly crosslinked network structure. When employed as a filler in mixed‐matrix membranes based on PIM‐1, a low loading of 0.5 wt% network‐PIM‐1 nanosheets gives rise to enhanced CO2 permeability and CO2/CH4 selectivity, compared to pure PIM‐1. [ABSTRACT FROM AUTHOR]

Keywords: modified electrodes; triphasic catalysis; ion conductivity; ionic diodes; gas diffusion electrodes Modified electrodes, triphasic catalysis, ion conductivity, ionic diodes, gas diffusion electrodes. [Extracted from the article]

The effect on the gas transport properties of Matrimid®5218 of blending with the polymer of intrinsic microporosity PIM-EA(H2)-TB was studied by pure and mixed gas permeation measurements. Membranes of the two neat polymers and their 50/50 wt % blend were prepared by solution casting from a dilute solution in dichloromethane. The pure gas permeability and diffusion coefficients of H2, He, O2, N2, CO2 and CH4 were determined by the time lag method in a traditional fixed volume gas permeation setup. Mixed gas permeability measurements with a 35/65 vol % CO2/CH4 mixture and a 15/85 vol % CO2/N2 mixture were performed on a novel variable volume setup with on-line mass spectrometric analysis of the permeate composition, with the unique feature that it is also able to determine the mixed gas diffusion coefficients. It was found that the permeability of Matrimid increased approximately 20-fold with the addition of 50 wt % PIM-EA(H2)-TB. Mixed gas permeation measurements showed a slightly stronger pressure dependence for selectivity of separation of the CO2/CH4 mixture as compared to the CO2/N2 mixture, particularly for both the blended membrane and the pure PIM. The mixed gas selectivity was slightly higher than for pure gases, and although N2 and CH4 diffusion coefficients strongly increase in the presence of CO2, their solubility is dramatically reduced as a result of competitive sorption. A full analysis is provided of the difference between the pure and mixed gas transport parameters of PIM-EA(H2)-TB, Matrimid®5218 and their 50:50 wt % blend, including unique mixed gas diffusion coefficients. [ABSTRACT FROM AUTHOR]

This paper presents a novel method for transient and steady state mixed gas permeation measurements, using a quadrupole residual gas analyser for the on-line determination of the permeate composition. The on-line analysis provides sufficiently quick response times to follow even fast transient phenomena, enabling the unique determination of the diffusion coefficient of the individual gases in a gas mixture. Following earlier work, the method is further optimised for higher gas pressures, using a thin film composite and a thick dense styrene-butadiene-styrene (SBS) block copolymer membrane. Finally, the method is used to calculate the CO2/CH4 mixed gas diffusion coefficients of the spirobisfluorene-based polymer of intrinsic microporosity, PIM-SBF-1. It is shown that the modest pressure dependence of the PIM-SBF-1 permeability can be ascribed to a much stronger pressure dependence of the diffusion coefficient, which partially compensates the decreasing solubility of CO2 with increasing pressure, typical for the strong sorption behaviour in PIMs. The characteristics of the instrument are discussed and suggestions are given for even more versatile measurements under stepwise increasing pressure conditions. This is the first report on mixed gas diffusion coefficients at different pressures in a polymer of intrinsic microporosity. [ABSTRACT FROM AUTHOR]

The gas transport properties of mixed matrix membranes (MMMs), prepared by dispersing nanoparticles of MOFs MIL-101(Cr) or MIL-177(Ti) into highly permeable Polymers of Intrinsic Microporosity PIM-EA-TB or PIM-TMN-Trip, were investigated. The homogeneity of the dispersion was confirmed by means of Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray (EDX) mapping analysis. Single gas time-lag measurements provided the permeability and ideal selectivity of different gas pairs, both after treatment of the MMMs with methanol and after natural aging over an extended period (up to 2000 days). This data demonstrated that the gas size-sieving pores of MIL-101(Cr) and MIL-177(Ti) and their good dispersion into the PIM matrix results in MMMs with enhanced gas separation performance, as compared to films composed solely of the polymer. The comparison of actual permeability with the Maxwell model for PIM-EA-TB with both MOFs confirmed the good dispersion and the absence of anomalies, whereas the inconsistency of permeability with prediction data for PIM-TMN-Trip suggests that the MOFs improved the polymer properties, stiffening or occupying the polymer free volume. In particular, the incorporation of MIL-101(Cr) into PIM-EA-TB significantly enhances the H 2 permeability from ∼6000 to 13,000 Barrer, with a concurrent increase of the H 2 /N 2 selectivity from 14 to 21. MIL-177(Ti) also enhances the H 2 /N 2 selectivity to 20 due to a slight reduction of the N 2 permeability. The addition of MIL-101(Cr) and MIL-177(Ti) into the ultra-permeable PIM-TMN-Trip showed more modest increases in H 2 permeability and H 2 /N 2 selectivity from 4.6 to ∼ 10. Hence the data for some of the MMMs surpass the 2008, and even approach the 2015/2019 Robeson's upper bounds, particularly for gas pairs including H 2. [Display omitted] • The MIL-101(Cr) and MIL-177(Ti) were loaded into PIM-EA-TB or PIM-TMN-Trip for fabrication of MMMs. • Smaller MIL-101 particle-size favour better compatibility with polymers than larger MIL-177. • Mixed gas experiments confirm an excellent separation performance under a long aging. • Data for some MMMs break the 2008 upper approaching the 2015/2019 Robeson's upper bounds. [ABSTRACT FROM AUTHOR]

Fournovel sulfur-containing polymers of intrinsic microporosity(PIMs) were evaluated for use in CO2/CH4gasseparation membranes by means of predictive molecular simulations.It was found that the introduction of sulfur into the monomer backboneprovides an extra, less shape-persistent site of contortion, whichresults in a less porous polymer framework. However, the CO2adsorption isotherms and isosteric heats of adsorption were greatlyincreased in sulfonyl-functionalized PIMs. In addition, the 1:1 mixed-gasadsorption selectivity values of sulfonyl PIMs were shown to be enhancedby the highly polar functionality, which was calculated to be 23 atatmospheric pressure, and 50 for the lowest pressures reported. Themixed-gas adsorption selectivity is shown to be exponentially relatedto the difference between the isosteric heats of adsorption of CO2and CH4normalized by the total void space (Δqst/φ), which is referredto as the adsorbility. The results presented in thiswork should facilitate the purposeful design and screening of newintrinsically microporous polymer membranes with increased CO2/CH4gas separation performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • First observation of electroosmotic flow in polymers of intrinsic microporosity. • Employing NMR to monitor water transport through a microhole membrane. • Rectified water transport associated with ionic diode characteristics. • Water transport via "piston mechanism" linked to the molecularly rigid polymer backbone. Tertiary-amine-based Polymers of Intrinsic Microporosity (PIMs) provide a class of highly porous molecularly rigid materials for the electrochemical transport of both ionic and neutral species. Here, the transport of water molecules together with chloride anions (i.e. the electroosmotic drag coefficient) is studied for the intrinsically microporous polyamine PIM-EA-TB immersed in aqueous 0.01 M NaCl (i) when protonated for pH < 4 or (ii) when not protonated for pH > 4. Preliminary data suggest that in both cases a high electroosmotic drag coefficient is observed based on direct H 2 O transport into a D 2 O-filled compartment (quantified by 1H-NMR). For PIM-EA-TB there is a strong pH dependence with a higher electroosmotic drag coefficient in less acidic solutions (going from approx. 400 H 2 O per anion at pH 3 to approx. 4000 H 2 O per anion at pH 7), although the underlying absolute rate of water transport at a fixed voltage of −1 V appears to be essentially pH independent. Water transport through the PIM-EA-TB microchannels is rationalised based on the relative populations of chloride anions and of water in the micropores (essentially a 'piston' mechanism). [ABSTRACT FROM AUTHOR]

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]

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]

Graphitic carbon nitride with photo-attached platinum nanoparticles of typically 2.5 nm diameter, Pt@g-C 3 N 4 , is known for photo-generation of hydrogen in aqueous environments and in the presence of hole quenchers. Here, the generation of photocurrents from photo‑hydrogen production is observed at a platinum electrode, driven by oxalate or glucose hole quenchers, and enhanced with a polymer of intrinsic microporosity PIM-1 coated over the Pt@g-C 3 N 4 deposit. The ability of PIM-1 to create triphasic conditions and to capture hydrogen leads to enhanced photocurrent responses, even in the presence of ambient oxygen. Effects are discussed in terms of triphasic solid|liquid|hydrogen gas-based electrode processes. A glucose-concentration-dependent (super-Langmuirian) photo-response is observed. Possible applications are proposed in glucose sensing and in hydrogen-mediated photovoltaics. Unlabelled Image • Triphasic photo-electrode enhanced with polymer of intrinsic microporosity • Hydrogen-mediated photo-anode avoiding charge carrier transport • Room temperature processing to give photo-anode • Glucose-concentration-dependent photo-responses [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The expansion of the use of polymeric membranes in gas separation requires the development of membranes based on new polymers with improved properties and their assessment under real operating conditions. In particular, the fabrication of ultrathin films of high performance polymers that can be used as the selective layer in composite membranes will allow large reductions in the amount of the expensive polymer used and, hence, the cost of membrane fabrication. In this contribution, two polymers of intrinsic microporosity (PIMs) with very different chain configurations (two-dimensional, 2D, chains or conventional contorted three-dimensional, 3D, conformation) have been compared in their ability to form ultrathin films, showing the relevance of polymer design to obtain compact and defect-free films. Monolayers of the 2D polymer PIM-TMN-Trip can be efficiently deposited onto poly[1-(trimethylsilyl)-1-propyne] (PTMSP) to obtain composite membranes with a CO 2 /N 2 selectivity similar to that of the corresponding thick membranes of the same PIM using only a small fraction of the selective polymer (less than 0.1%). [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 Composite membranes were developed for gas separation applications, both as flat-sheets and hollow fibres, using a Polymer of Intrinsic Microporosity, composed of Tröger's base, TB, and of ethanoanthracene (PIM-EA(H 2)-TB) as the selective layer. The crucial role of the solvent, dichloromethane and chloroform, used in membrane preparation on the transport properties was evaluated by both thermogravimetric analysis and permeation tests on PIM-EA(H 2)-TB dense self-supported films. Molecular modelling, reproducing the experimental conditions in presence of the two different solvents, was performed to investigate the role of the solvent on the morphological and transport properties of the PIM polymer. The strong interaction of the polymer matrix with chloroform reduces gas permeability due to the partial saturation of the sorption sites and the competition between solvent and permeating gas molecules. Consequently, dichloromethane was chosen as suitable solvent in composite membrane preparation also for its good compatibility with PAN. PAN-based hollow fibres were prepared according to phase inversion method and used as porous supports. They were functionalised by partial conversion of the nitrile groups into carboxyl groups to improve compatibility with the active PIM layer. Controlled temperature and humidity conditions during the coating process reduced the presence of micropores on the membrane surface, favouring the formation of a dense layer on the hollow fibre porous support. Composite PIM-EA(H 2)-TB membranes were successfully developed having selectivity similar to the dense membranes for different gas pairs. Graphical abstract fx1 Highlights • The role of the solvent on gas transport in PIM-EA(H 2)-TB films was evaluated by permeation tests and molecular modelling. • Thin film PIM-EA(H 2)-TB composite membranes were developed as flat-sheets and hollow fibres. • PAN-based hollow fibres, prepared ad hoc and properly functionalized, were the supports for the selective PIM-EA(H 2)-TB layer. • Composite membranes showed selectivity values close to the dense membranes in gas separation. [ABSTRACT FROM AUTHOR]

Triphasic microporous materials (containing solid, liquid, and gas) are of interest in electrocatalysis. In this exploratory study, a polymer of intrinsic microporosity (PIM-EA-TB) is impregnated with PdCl 4 2 − metal precursor and vacuum‑carbonised to give an electrically conductive microporous heterocarbon with embedded Pd nanoparticles of typically 10–30 nm diameter. This microporous composite catalyst is formed (via spin-coating) as “flakes” of typically 100 nm thickness and 1 to 20 μm diameter that are readily re-deposited onto glassy carbon electrode substrates. Due to the triphasic conditions, Pd@cPIM electrocatalytic reactivity is high but only for gases (H 2 oxidation or O 2 reduction). This selectivity is observed even in the presence of excess formic acid fuel in the aqueous/liquid phase. The potential for application in membrane-less micro-fuel cells is discussed. [ABSTRACT FROM AUTHOR]

“Heterojunction” ionic diodes based on a Nafion cation conductor and a polymer of intrinsic microporosity (PIM) interfaced at a 6 μm thickness polyethylene-terephthalate (PET) film with 20 μm diameter microhole exhibit rectification effects in cation (K + ) flux. When combined with the precipitation reaction of potassium cations with perchlorate anions to give insoluble KClO 4 (solubility product ca. 1.05 × 10 −2 M 2 at 25 °C) at the PIM | Nafion interface, inversion of the rectification/diode effect occurs and the formerly “open” state changes into a “closed” state due to blocking of ion flow. The localised interfacial precipitation reaction is due to up to three orders of magnitude accumulation of K + at the PIM | Nafion interface and shown to be fast and reversible. The effects of K + /ClO 4 − concentration and of Na + interference are considered. The blocking process within the heterojunction ionic diode is suggested to be dynamic/fast and potentially useful as a diode sensor mechanism based on solubility product dependent precipitation. [ABSTRACT FROM AUTHOR]

Tröger's base (TB) is often used as a building block for the synthesis of Polymers of Intrinsic Microporosity (PIMs) due to its rigid bicyclic V-shaped structure. In this study the TB component in the structure of a PIM is replaced by 2,3:6,7-dibenzobicyclo[3.3.1]nonane, a purely carbocyclic analogue of TB. This modification results in only a slightly reduced amount of microporosity as determined using nitrogen adsorption. Further comparisons with previously reported PIMs indicate that this building unit (and therefore TB) is significantly less effective for the generation of intrinsic microporosity than spirobisindane, a commonly used structural unit for PIM synthesis. It appears that the V-shape of the 2,3:6,7-dibenzobicyclo[3.3.1]nonane and TB units allows closer contact between polymer chains thereby enhancing packing efficiency. [ABSTRACT FROM AUTHOR]

The initially very promising transport properties of glassy high free volume polymers deteriorate rapidly over time. In this work, we focused on this aging phenomenon in two polymers of intrinsic microporosity (PIMs), namely PIM-1 and PIM-EA-TB. To identify the main mechanisms involved, we studied the time-declines of permeability and diffusivity of methanol vapours in flat membranes with approximately equal thicknesses. The permeation measurements were carried out using a continuous flow permeation method with carrier gas, where the methanol vapours were held at constant activity 0.2 at 25 °C. Two different experimental modes were used: (i) continuous experiments that consisted of one long experiment with a duration of over 650 h for each polymer and (ii) momentary experiments that consisted of a vast number of short ( ca. 6 h) consecutive measurements of transient permeation. The observed decreases of methanol permeability due to aging were more intense in the case of continuous mode for both polymers. In other words, the aging was ca. 1.3 times faster in the continuous mode in comparison with the momentary mode. Using time-aging time superposition, we successfully predicted the continuous experiments from the momentary experiments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxygen gas binding into PIM-1 as a factor in electrochemical reduction of oxygen. • Generator–collector voltammetry with printed electrodes under controlled gas atmosphere. • First quantitative evaluation of gas storage in PIM-1 in aqueous environment. • Enhanced hydrogen peroxide production at graphene foam electrodes. 3D-graphene foam electrodes (Gii-Sens) immersed in a phosphate buffer solution of pH 7 are shown to generate hydrogen peroxide at a significantly faster rate in the presence of a nanoparticulate polymer of intrinsic microporosity (PIM-1). The effect is demonstrated to be associated at least in part with oxygen binding into PIM-1 under triphasic conditions. The release of the oxygen at the electrode|solution interface quadruples H 2 O 2 production. Generator–collector experiments are performed with a graphene foam disk generator and a platinum disk electrode collector to allow in situ detection of hydrogen peroxide and oxygen. [ABSTRACT FROM AUTHOR]

“Ionic diode” (or current rectification) effects are potentially important for a range of applications including water purification. In this preliminary report, we observe novel ionic diode behaviour of thin (300 nm) membranes based on a polymer of intrinsic microporosity (PIM-EA-TB) supported on a poly-ethylene-terephthalate (PET) film with a 20 μm diameter microhole, and immersed in aqueous electrolyte media. Current rectification effects are observed for half-cells with the same electrolyte solution on both sides of the membrane for cases where cation and anion mobility differ (HCl, other acids, NaOH, etc.) but not for cases where cation and anion mobility are more alike (LiCl, NaCl, KCl, etc.). A pH-dependent reversal of the ionic diode effect is observed and discussed in terms of tentatively assigned mechanisms based on both (i) ion mobility within the PIM-EA-TB nano-membrane and (ii) a possible “mechanical valve effect” linked to membrane potential and electrokinetic movement of the membrane as well as hydrostatic pressure effects. [ABSTRACT FROM AUTHOR]

A series of four novel Tröger's base (TB) derived polyimides of intrinsic microporosity (PIM-TB-PI) is reported. The TB diamine monomer (4MTBDA) possesses four methyl groups in order to restrict rotation about the C-N imide bonds in the resulting polymers. The polymers possess apparent BET (Brunauer, Emmett, and Teller) surface areas between 584 and 739 m² g-1, complete solubility in chloroform, excellent molecular mass, high inherent viscosity and good film-forming properties. Gas permeability measurements demonstrate enhanced performance over previously reported polyimide-based Tröger's base (TB) polymers confirming the benefit of the additional methyl groups within the TB diamine monomer. Notably, a polyimide derived from 4MTBDA and pyromellitic anhydride (PMDA) demonstrates gas permeability data above the 2008 upper bounds for important gas pairs such as O2/N2, H2/N2, and H2/CH4. [ABSTRACT FROM AUTHOR]

The limited stability of fuel cell cathode catalysts causes a significant loss of operational cell voltage with commercial Pt-based catalysts, which hinders the wider commercialization of fuel cell technologies. We demonstrate beneficial effects of a highly rigid and porous polymer of intrinsic microporosity (PIM-EA-TB with BET surface area 1027 m 2 g − 1 ) in accelerated catalyst corrosion experiments. Porous films of PIM-EA-TB offer an effective protective matrix for the prevention of Pt/C catalyst corrosion without impeding flux of reagents. The results of electrochemical cycling tests show that the PIM-EA-TB protected Pt/C (denoted here as PIM@Pt/C) exhibit a significantly enhanced durability as compared to a conventional Pt/C catalyst. [ABSTRACT FROM AUTHOR]