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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., (© 2021. Springer-Verlag GmbH Germany, part of Springer Nature.)

CO 2 reduction offers an attractive alternative green synthetic route for ethylene, especially where CO 2 could be sourced from industrial exhausts and in combination with green power sources. However, practical applications are currently limited due to the unfortunately low selectivity of cathode materials towards ethylene. This work uses polymers with intrinsic microporosity (PIMs) to improve the performance of copper gas diffusion electrodes for CO 2 reduction to ethylene. We report an improved selectivity and activity towards ethylene with the addition of a thin PIMs layer, which is seen as improved Faradaic efficiency, increased stability and a shift in the reduction to lower overpotential. This improvement is highly dependent on the thickness of the added polymer layer, with too thick a layer having a detrimental impact on the hydrophobicity of the gas diffusion layer. With a compromise in loading, PIMs can be used to enhance the activity and selectivity of catalysts for targeted CO 2 reduction to ethylene., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Microporous polymer nanosheets with thicknesses in the range 3-5 nm and with high apparent surface area (Brunauer-Emmett-Teller surface area 940 m 2 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 CO 2 permeability and CO 2 /CH 4 selectivity, compared to pure PIM-1., (© 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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 CO 2 permeance up to seven times higher than dense PIM membranes using only 0.04 % of the mass of PIM without a significant decrease in CO 2 /N 2 selectivity., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A highly gas-permeable polymer with enhanced selectivities is prepared using spirobifluorene as the main structural unit. The greater rigidity of this polymer of intrinsic microporosity (PIM-SBF) facilitates gas permeability data that lie above the 2008 Robeson upper bound, which is the universal performance indicator for polymer gas separation membranes., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This work explores the use of a polymer of intrinsic microporosity (PIM-1) as the active layer within a laser sensor to detect nitroaromatic-based explosive vapors. We show successful detection of dinitrobenzene (DNB) by monitoring the real-time photoluminescence. We also show that PIM-1 has an inherent memory, so that it accumulates the analyte during exposure. In addition, the optical gain and refractive index of the polymer were studied by amplified spontaneous emission and variable-angle ellipsometry, respectively. A second-order distributed feedback PIM-1 laser sensor was fabricated and found to show an increase in laser threshold of 2.5 times and a reduction of the laser slope efficiency by 4.4 times after a 5-min exposure to the DNB vapor. For pumping at 2 times threshold, the lasing action was stopped within 30 s indicating that PIM-1 has a very fast responsivity and as such has a potential sensing ability for ultra-low-concentration explosives.

The challenge of storing hydrogen at high volumetric and gravimetric density for automotive applications has prompted investigations into the potential of cryo-adsorption on the internal surface area of microporous organic polymers. A range of Polymers of Intrinsic Microporosity (PIMs) has been studied, the best PIM to date (a network-PIM incorporating a triptycene subunit) taking up 2.7% H(2) by mass at 10 bar/77 K. HyperCrosslinked Polymers (HCPs) also show promising performance as H(2) storage materials, particularly at pressures >10 bar. The N(2) and H(2) adsorption behaviour at 77 K of six PIMs and a HCP are compared. Surface areas based on Langmuir plots of H(2) adsorption at high pressure are shown to provide a useful guide to hydrogen capacity, but Langmuir plots based on low pressure data underestimate the potential H(2) uptake. The micropore distribution influences the form of the H(2) isotherm, a higher concentration of ultramicropores (pore size <0.7 nm) being associated with enhanced low pressure adsorption.

This tutorial review describes recent research directed towards the synthesis of polymer-based organic microporous materials termed Polymers of Intrinsic Microporosity (PIMs). PIMs can be prepared either as insoluble networks or soluble polymers with both types giving solids that exhibit analogous behaviour to that of conventional microporous materials such as activated carbons. Soluble PIMs may be processed into thin films for use as highly selective gas separation membranes. Preliminary results also demonstrate the potential of PIMs for heterogeneous catalysis and hydrogen storage.

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]

Redox flow batteries (RFBs) are promising for large‐scale long‐duration energy storage owing to their inherent safety, decoupled power and energy, high efficiency, and longevity. Membranes constitute an important component that affects mass transport processes in RFBs, including ion transport, redox‐species crossover, and the net volumetric transfer of supporting electrolytes. Hydrophilic microporous polymers, such as polymers of intrinsic microporosity (PIM), are demonstrated as next‐generation ion‐selective membranes in RFBs. However, the crossover of redox species and water migration through membranes are remaining challenges for battery longevity. Here, a facile strategy is reported for regulating mass transport and enhancing battery cycling stability by employing thin film composite (TFC) membranes prepared from a PIM polymer with optimized selective‐layer thickness. Integration of these PIM‐based TFC membranes with a variety of redox chemistries allows for the screening of suitable RFB systems that display high compatibility between membrane and redox couples, affording long‐life operation with minimal capacity fade. Thickness optimization of TFC membranes further improves cycling performance and significantly restricts water transfer in selected RFB systems. [ABSTRACT FROM AUTHOR]

Urine citrate analysis is relevant in the screening and monitoring of patients with prostate cancer and calcium nephrolithiasis. A sensitive, fast, easy, and low-maintenance electrochemiluminescence (ECL) method with conductivity detection for the analysis of citrate in urine is developed and validated by employing polymer of intrinsic microporosity-1 nanoparticles/nitrogen-doped carbon quantum dots (nano-PIM-1/N-CQDs). Using optimum conditions, the sensor was applied in ECL experiments in the presence of different concentrations of citrate ions. The ECL signals were quenched gradually by the increasing citrate concentration. The linear range of the relationship between the logarithm of the citrate concentration and ΔECL (ECL of blank − ECL of sample) was obtained between 1.0 × 10−7 M and 5.0 × 10−4 M. The limit of detection (LOD) was calculated to be 2.2 × 10−8 M (S/N = 3). The sensor was successfully applied in real samples such as human serum and patient urine. [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]

Redox flow batteries (RFBs) based on aqueous organic electrolytes are a promising technology for safe and cost‐effective large‐scale electrical energy storage. Membrane separators are a key component in RFBs, allowing fast conduction of charge‐carrier ions but minimizing the cross‐over of redox‐active species. Here, we report the molecular engineering of amidoxime‐functionalized Polymers of Intrinsic Microporosity (AO‐PIMs) by tuning their polymer chain topology and pore architecture to optimize membrane ion transport functions. AO‐PIM membranes are integrated with three emerging aqueous organic flow battery chemistries, and the synergetic integration of ion‐selective membranes with molecular engineered organic molecules in neutral‐pH electrolytes leads to significantly enhanced cycling stability. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g‐C3N4) with photo‐attached platinum (Pt@g‐C3N4) is known to generate hydrogen under illumination in aqueous environments in the presence of carbohydrate hole quenchers. Here, Pt@g‐C3N4 is embedded into a polymer of intrinsic microporosity (PIM‐1) host material with a molecularly rigid structure to maintain active unblocked catalyst surfaces and to control transport to/from the photocatalyst. A Clark‐type oxygen/hydrogen sensor is employed with Pt@g‐C3N4 embedded into PIM‐1 applied as a film to be the gas‐permeable sensor membrane. Oxygen reduction and hydrogen production are observed in situ as a function of light exposure and quencher concentration. Significant size‐selectivity favouring smaller more flexible saccharides or carbohydrate/ hydrocarbon quenchers is observed and attributed to rate limiting PIM‐1 micropore transport. Effective hydrogen production through a Teflon membrane is demonstrated. The underlying hydrogen production/ photocurrent enhancing effects of the microporous PIM‐1 film on the photochemical process are revealed. [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]

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]

Abstract: Membrane separation for gas purification is an energy‐efficient and environment‐friendly technology. However, the development of high performance membranes is still a great challenge. In principle, mixed matrix membranes (MMMs) have the potential to overcome current materials limitations, but in practice there is no straightforward method to match the properties of fillers and polymers (the main components of MMMs) in such a way that the final membrane performance reflects the high performance of the microporous filler and the processability of the continuous polymer phase. This issue is especially important when high flux polymers are utilized. In this work, we demonstrate that the use of small amounts of a glassy polymer in combination with high performance PIM‐1 allow for the preparation of metal–organic framework (MOF)‐based MMMs with superior separation properties and low aging rates under humid conditions, meeting the commercial target for post‐combustion CO2 capture. [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]

The development of polymeric anion-exchange membranes (AEMs) combining high ion conductivity and long-term stability is a major challenge for materials chemistry. AEMs with regularly distributed fixed cationic groups, based on the formation of microporous polymers containing the V-shape rigid Tröger's base units, are reported for the first time. Despite their simple preparation, which involves only two synthetic steps using commercially available precursors, the polymers provide AEMs with exceptional hydroxide conductivity at relatively low ion-exchange capacity, as well as a high swelling resistance and chemical stability. An unprecedented hydroxide conductivity of 164.4 mS cm−1 is obtained at a relatively a low ion-exchange capacity of 0.82 mmol g−1 under optimal operating conditions. The exceptional anion conductivity appears related to the intrinsic microporosity of the charged polymer matrix, which facilitates rapid anion transport. [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 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 work explores the use of a polymer of intrinsic microporosity (PIM-1) as the active layer within a laser sensor to detect nitroaromatic-based explosive vapors. We show successful detection of dinitrobenzene (DNB) by monitoring the real-time photoluminescence. We also show that PIM-1 has an inherent memory, so that it accumulates the analyte during exposure. In addition, the optical gain and refractive index of the polymer were studied by amplified spontaneous emission and variable-angle ellipsometry, respectively. A second-order distributed feedback PIM-1 laser sensor was fabricated and found to show an increase in laser threshold of 2.5 times and a reduction of the laser slope efficiency by 4.4 times after a 5-min exposure to the DNB vapor. For pumping at 2 times threshold, the lasing action was stopped within 30 s indicating that PIM-1 has a very fast responsivity and as such has a potential sensing ability for ultra-low-concentration explosives. [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]

Microporous polymers derived from the 1,2- and 1,4-regioisomers of di(3′,4′-dihydroxyphenyl)tetraphenylbenzene have very different properties with the former being composed predominantly of cyclic oligomers whereas the latter is of high molar mass suitable for the formation of robust solvent-cast films of high gas permeability. [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]

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]

Graphical abstract Highlights • New microporous polymer networks based on porphyrins as monomers (PIM). • New microporous polymer networks with apparent BET surface areas in the range 600–1200 m2g−1. • New insoluble metalloporphyrins derivatives as catalysts in heterogeneous medium. • New examples of PIM materials with high catalytic activity and selectivity in oxidation process. • PIM materials with thermal and chemical stability and good recyclability. Abstract New microporous polymer networks, constructed by a nucleophilic substitution reaction between two different porphyrins and metalloporphyrins are reported. The meso -tetrakis-(pentafluorophenyl)porphyrin HP1 (monomer A1) and/or its manganese complex MP1 (monomer A2) was reacted with the meso -tetrakis-(3,4-dihydroxyphenyl)porphyrin HP2 (monomer B1) and/or its manganese complex MP2 (monomer B2), giving rise to four new porphyrin-based microporous network polymers (P1 - P4) with apparent BET surface areas in the range 600–1200 m2 g−1. The catalytic performance of the polymers was evaluated by oxidation reactions using cyclooctene and cyclohexane as substrates and Iodosylbenzene as oxidant in cytochrome P-450 model reactions. The catalytic activity and selectivity of these porous polymer networks are similar or superior to those of the analogous homogeneous manganese porphyrins MP1 and MP2. The robustness of the materials in terms of thermal stability and good recyclability showed that they hold great promise as biomimetic heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Palladium nanoparticles embedded in a polymer of intrinsic microporosity (PIM-EA-TB) acts as artificial formate oxidase. • Surface cavities formed by PIM-EA-TB allow doubling the H 2 O 2 production by protonation of tertiary amines. • Percholrate anions enhance H 2 O 2 production. • A DFT model confirms artificial formate oxidase reaction pathway. • A blue colour linked to H 2 O 2 formation in the presence of TMB is accumulated into a printed Nafion pattern. Surface cavities formed by molecularly rigid polymers of intrinsic microporosity affect catalytic processes. Palladium nanoparticles of typically 3 nm diameter are formed in an intrinsically microporous polyamine (PIM-EA-TB) by borohydride reduction. These particles are shown to indirectly catalyse the oxidative colour change of indicator dye 3,5,3′,5′-tetramethylbenzidine (TMB) in the presence of formic acid via formation of H 2 O 2. Investigation reveals that oxygen reduction on the palladium is rate limiting with optimised H 2 O 2 production at approximately pH 3 to 4, and first order in formate, followed by purely homogeneous TMB oxidation. The H 2 O 2 production is therefore studied separately as a nanozyme-like catalytic process equivalent to formate oxidase reactivity, linked to the molecularly rigid polyamine host (PIM-EA-TB) providing ammonium sites (in molecularly rigid surface cavities) that enhance both (i) 2-electron formate oxidation and (ii) 2-electron oxygen reduction to H 2 O 2. Beneficial effects of hydrophobic ClO 4 - anions are noted as indirect evidence for the effect of ammonium sites in surface cavities. A computational DFT model for the artificial formate oxidase reactivity is developed to underpin and illustrate the hypothesis of PIM-EA-TB as an active catalyst component with implications for future nanozyme sensor development. [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]

Abstract: The synthesis of novel monomers based upon the rigid 1,1′-spiro-bis(1,2,4,5-tetrahydro-6,7-dihydroxynaphthalene) framework is reported. These monomers can be used for the synthesis of polymers of intrinsic microporosity (PIMs) due to their reactive catechol units and nonlinear shape, which introduces the necessary sites of contortion into the resulting PIM. [Copyright &y& Elsevier]

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]

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]

[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]

The enzymeless and operationally simple electrocatalytic oxidation of carbohydrates by “heterogenised” 4-benzoyloxy-TEMPO either (i) immobilised as microcrystals at a glassy carbon electrode surface or (ii) embedded into a polymer of intrinsic microporosity (PIM-EA-TB with 1027 m 2 g −1 BET surface area and highly rigid framework structure) has been studied in aqueous phosphate buffer of pH 12. It is shown that in contrast to microcrystal deposits, 4-benzolyoxy-TEMPO co-immobilised within PIM-EA-TB give stable catalytic responses for both, stationary and rotating disc electrode systems and for oxidation of glucose, sorbitol, and sucrose. The rigidity and intrinsic microporosity of PIM-EA-TB allow (slow) substrate and product diffusion, whilst maintaining 4-benzoyloxy-TEMPO immobilised in active molecular form. [ABSTRACT FROM AUTHOR]

A water-insoluble Polymer with Intrinsic Microporosity (or PIM, here for the particular case of the Tröger Base system PIM-EA-TB, BET area ca. 10 3 m 2 g - 1 ) is demonstrated to act as a rigid host environment for highly water-insoluble molecular catalysts, here tetraphenylporphyrinato-iron (FeTPP), surrounded by aqueous solution-filled micropores. A PIM-EA-TB film containing catalyst is deposited onto the electrode and immersed for voltammetry (i) with 4-(3-phenyl-propyl)-pyridine to give an organogel, or (ii) bare directly into aqueous solution. The porous host allows processes to be optimised as a function of solution phase, composition, and catalyst loading. Effective electron transfer as well as effective electrocatalysis is reported for aqueous oxygen and peroxide reduction. Given the use of completely water-insoluble catalyst systems, the methodology offers potential for application with a wide range of hitherto unexplored molecular electrocatalysts and catalyst combinations in aqueous media. [ABSTRACT FROM AUTHOR]

Abstract: Sorbent hollow fibres, generally prepared by fully encapsulating an adsorbent within a polymer binder such as polyethersulfone (PES), provide a low pressure drop alternative to conventional packed beds. These fibres have a high external surface area to volume ratio, enabling smaller bed sizes, and a highly porous structure resulting in low mass transfer resistance while maximising sorption efficiency. However, adsorbent hollow fibres prepared with PES suffer from loss of some adsorption capacity due to the polymer binder. This paper describes a novel formulation of composite hollow fibres containing activated carbon and PIM-1, a polymer of intrinsic microporosity, as an active binder designed to enhance the total adsorption capacity. Octane has been selected as a model hydrocarbon, and nitrogen and octane isotherms are reported for both PES and PIM-1 based hollow fibres, each containing the same activated carbon. Theoretical BET surface areas were calculated for each type of fibre based on a weighted average of the surface areas of its individual components (i.e. polymer and carbon). The measured surface area of the PIM-1 fibres was remarkably consistent with the theoretical value, while the measured surface area and octane uptake for PES fibres were ∼10% lower than the theoretical values, indicating some blockage of the adsorbent by the polymer matrix. PIM-1 adsorbent fibres were found to fully utilise the capacity of the supported carbon, as well as providing additional sites for adsorption on the polymer, resulting in a maximum octane uptake of 50%w/w – approximately twice that of the PES-based fibres. [Copyright &y& Elsevier]