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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]

Polymers of intrinsic microporosity (PIMs) offer a useful combination of processability and inherent microporous features arising from their contorted and rigid structures, with the potential for the immobilisation of light harvesting groups for use in photochemistry. Herein, we report on the chemical incorporation of photosensitisers based on the benzo[c][1,2,5]thiadiazole (BTZ) group into PIM-EA-TB through a copolymerisation strategy, allowing up to 5% BTZ incorporation without compromising processability or microporosity. The BTZ-doped PIMs were then utilised as either homogeneous or heterogeneous visible light photosensitisers of oxygen under both batch and continuous flow conditions. The advantages of the solution processability of these materials was demonstrated by the simple deposition of the photoactive microporous polymer onto glass beads, which were then fixed within a column reactor for continuous flow photochemistry. [ABSTRACT FROM AUTHOR]

Ionic diodes are components in ionic circuits for AC‐electricity driven desalination and ion extraction processes. Independent of the ionic diode type/mechanism, achieving ionic current rectification at high ionic strengths is challenging but important, for example in seawater desalination and treatment of brine. Here, the butylation of a molecularly rigid (glassy) polymer of intrinsic microporosity (PIM‐EA‐TB) is shown to give anionic diodes with ultrahigh rectification effects (associated with interfacial resistivity) even in high ionic strength aqueous 2 M NaCl solution. The effect is rationalised based on polymer structure affecting ion transport. [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]

Polymeric carbon nitrides (C3N4) are photochemically active organic semiconductors that can be produced in a wide range of structural types. Here, a poly-(heptazine imide) containing nickel single atoms (Ni-PHI) is employed for photochemical hydrogen production and is compared to the non-nickel-doped semiconductor. Film deposits are formed on a platinum disk electrode (to detect hydrogen) and a coating of the molecularly rigid polymer of intrinsic microporosity PIM-1 is applied to (i) mechanically stabilize the photo-catalyst film without impeding photocatalysis and (ii) assist in the interfacial hydrogen capture/oxygen suppression process. In the presence of hole quenchers such as methanol or ethanol, anodic photocurrents linked to hydrogen production/oxidation are observed. A comparison with an experiment on glassy carbon confirms the formation of interfacial hydrogen as a mediator. The effects of hole quencher concentration are evaluated. The system Pt/Ni-PHI/PIM-1 is employed in a single-compartment photo-fuel cell. [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]

A blue light mediated photochemical process using solid graphitic carbon nitride (g-C3N4) in ambient air/isopropanol vapour is suggested to be linked to "nanophase" water inclusions and is shown to produce approx. 50 μmol H2O2 per gram of g-C3N4, which can be stored in the solid g-C3N4 for later release for applications, for example, in disinfection or anti-bacterial surfaces. [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]

The enhancement of separation processes and electrochemical technologies such as water electrolysers1,2, fuel cells3,4, redox flow batteries5,6 and ion-capture electrodialysis7 depends on the development of low-resistance and high-selectivity ion-transport membranes. The transport of ions through these membranes depends on the overall energy barriers imposed by the collective interplay of pore architecture and pore–analyte interaction8,9. However, it remains challenging to design efficient, scaleable and low-cost selective ion-transport membranes that provide ion channels for low-energy-barrier transport. Here we pursue a strategy that allows the diffusion limit of ions in water to be approached for large-area, free-standing, synthetic membranes using covalently bonded polymer frameworks with rigidity-confined ion channels. The near-frictionless ion flow is synergistically fulfilled by robust micropore confinement and multi-interaction between ion and membrane, which afford, for instance, a Na+ diffusion coefficient of 1.18 × 10−9 m2 s–1, close to the value in pure water at infinite dilution, and an area-specific membrane resistance as low as 0.17 Ω cm2. We demonstrate highly efficient membranes in rapidly charging aqueous organic redox flow batteries that deliver both high energy efficiency and high-capacity utilization at extremely high current densities (up to 500 mA cm–2), and also that avoid crossover-induced capacity decay. This membrane design concept may be broadly applicable to membranes for a wide range of electrochemical devices and for precise molecular separation.The authors develop a strategy that allows the diffusion limit of ions in water to be approached for large-area, free-standing, synthetic membranes using covalently bonded polymer frameworks with rigidity-confined ion channels. [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]

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]

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]

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]

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]

Redox flow batteries using aqueous organic-based electrolytes are promising candidates for developing cost-effective grid-scale energy storage devices. However, a significant drawback of these batteries is the cross-mixing of active species through the membrane, which causes battery performance degradation. To overcome this issue, here we report size-selective ion-exchange membranes prepared by sulfonation of a spirobifluorene-based microporous polymer and demonstrate their efficient ion sieving functions in flow batteries. The spirobifluorene unit allows control over the degree of sulfonation to optimize the transport of cations, whilst the microporous structure inhibits the crossover of organic molecules via molecular sieving. Furthermore, the enhanced membrane selectivity mitigates the crossover-induced capacity decay whilst maintaining good ionic conductivity for aqueous electrolyte solution at pH 9, where the redox-active organic molecules show long-term stability. We also prove the boosting effect of the membranes on the energy efficiency and peak power density of the aqueous redox flow battery, which shows stable operation for about 120 h (i.e., 2100 charge-discharge cycles at 100 mA cm−2) in a laboratory-scale cell. Aqueous organic redox flow batteries are promising for grid-scale energy storage, although their practical application is still limited. Here, the authors report highly ion-conductive and selective polymer membranes, which boost the battery's efficiency and stability, offering cost-effective electricity storage. [ABSTRACT FROM AUTHOR]

Binding of PdCl42− into the polymer of intrinsic microporosity PIM-EA-TB (on a Nylon mesh substrate) followed by borohydride reduction leads to uncapped Pd(0) nano-catalysts with typically 3.2 ± 0.2 nm diameter embedded within the microporous polymer host structure. Spontaneous reaction of Pd(0) with formic acid and oxygen is shown to result in the competing formation of (i) hydrogen peroxide (at low formic acid concentration in air; with optimum H2O2 yield at 2 mM HCOOH), (ii) water, or (iii) hydrogen (at higher formic acid concentration or under argon). Next, a spontaneous electroless gold deposition process is employed to attach gold (typically 10- to 35-nm diameter) to the nano-palladium in PIM-EA-TB to give an order of magnitude enhanced production of H2O2 with high yields even at higher HCOOH concentration (suppressing hydrogen evolution). Pd and Au work hand-in-hand as bipolar electrocatalysts. A Clark probe method is developed to assess the catalyst efficiency (based on competing oxygen removal and hydrogen production) and a mass spectrometry method is developed to monitor/optimise the rate of production of hydrogen peroxide. Heterogenised Pd/Au@PIM-EA-TB catalysts are effective and allow easy catalyst recovery and reuse for hydrogen peroxide production. [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]

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‐EA‐TB provides a molecularly rigid micropore structure containing tertiary amine sites and is shown here to interact with hydrogen bonding guest molecules such as caffeic acid. Voltammetric data with a PIM‐EA‐TB film on glassy carbon electrodes show that in both acidic solution (pH 2; PIM‐EA‐TB is protonated) and in neutral solution (pH 6; PIM‐EA‐TB is not protonated) caffeic acid is slowly accumulated into the microporous host. Binding constants are estimated and suggested to be linked to hydrogen bonding causing accumulation of caffeic acid. When employing PIM‐EA‐TB as an asymmetric membrane coated onto a 5 μm thick Teflon support film with 10 μm diameter microholes (using either a single microhole or a 10×10 array of microholes), binding of caffeic acid is shown to cause a modulation of the ionic current without affecting the pH‐dependent ionic diode behaviour. Two complementary types of effects of caffeic acid guests are discussed based on blocking anion diffusion pathways and based on removal of positive charges. The caffeic acid transport mechanism/efficiency is investigated in view of selective molecular pumping. [ABSTRACT FROM AUTHOR]

A series of nine polymers of intrinsic microporosity (PIMs) derived from different bis-catechol monomers and 2,3,7,8-tetrafluoro-5,5′,10,10′-tetraoxidethianthrene (TOT) were synthesised and tested for their potential use as gas separation membranes. As powders, they demonstrate significant nitrogen adsorption at 77 K allowing apparent BET surface areas ranging from 432–785 m2 g−1 to be calculated. Six of the polymers were found to be soluble in quinoline facilitating the casting of self-standing films to allow the assessment of their gas separation properties. Spirobifluorene-based polymers exhibited the highest gas permeability, approaching the performance of the archetypal PIM-1, and the data for some are placed close to the 2008 Robeson upper bounds for O2/N2 and CO2/CH4. Ageing studies showed a gradual decrease in permeability, accompanied by an increase in selectivity that moved the data more-or-less parallel to the Robeson upper bounds. The two polymers with the lowest and highest gas permeability were both tested over the temperature range 25–55 °C and an enhancement in permeability for all gases, with the exception of CO2, was observed along with decreased selectivity for almost all gas pairs. The latter seems to be due to the simultaneous drop in both diffusivity selectivity and solubility selectivity for all gas pairs, but especially those involving CO2, due to a strong decrease in solubility with increasing temperature. The analysis of the energetic and entropic selectivity provides further insight into the remarkable transport properties of PIMs. Overall, the tetraoxidethianthrene unit proves to be a suitable building block for use in PIM synthesis for applications in gas separation membranes and these PIMs have a one to two orders of magnitude higher permeability than more common polysulfones. [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]

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]

Membranes which allow fast and selective transport of protons and cations are required for a wide range of electrochemical energy conversion and storage devices, such as proton‐exchange membrane (PEM) fuel cells (PEMFCs) and redox flow batteries (RFBs). Herein we report a new approach to designing solution‐processable ion‐selective polymer membranes with both intrinsic microporosity and ion‐conductive functionality. Polymers are synthesized with rigid and contorted backbones, which incorporate hydrophobic fluorinated and hydrophilic sulfonic acid functional groups, to produce membranes with negatively charged subnanometer‐sized confined ionic channels. The ready transport of protons and cations through these membranes, and the high selectivity towards nanometer‐sized redox‐active molecules, enable efficient and stable operation of an aqueous alkaline quinone redox flow battery and a hydrogen PEM fuel cell. [ABSTRACT FROM AUTHOR]

Membranes which allow fast and selective transport of protons and cations are required for a wide range of electrochemical energy conversion and storage devices, such as proton‐exchange membrane (PEM) fuel cells (PEMFCs) and redox flow batteries (RFBs). Herein we report a new approach to designing solution‐processable ion‐selective polymer membranes with both intrinsic microporosity and ion‐conductive functionality. Polymers are synthesized with rigid and contorted backbones, which incorporate hydrophobic fluorinated and hydrophilic sulfonic acid functional groups, to produce membranes with negatively charged subnanometer‐sized confined ionic channels. The ready transport of protons and cations through these membranes, and the high selectivity towards nanometer‐sized redox‐active molecules, enable efficient and stable operation of an aqueous alkaline quinone redox flow battery and a hydrogen PEM fuel cell. [ABSTRACT FROM AUTHOR]

An analysis of the diffusivity of light gases through Polymers of Intrinsic Microporosity (PIMs) shows that smaller H2 and He gas molecules have a transport mechanism that is similar to that of porous materials, whereas larger gas molecules, CH4, N2, O2 and CO2, show activated transport similar to that of conventional dense polymers. A typical and defining feature of PIMs, which differentiates their properties from other high free volume polymers, glassy polymers and rubbers, is the change in slope of the plot of the diffusion coefficient as a function of the gas diameter, with a stronger size-selective trend for the larger gas molecules than for He and H2. Deviation from this trend is observed for a polymer-gas combination with strong mutual affinity (i.e. an amine modified PIM with CO2). Molecular modelling shows that size selectivity in PIMs originates from the presence of bottlenecks between the individual free volume elements. For the latest generation of highly rigid PIMs, ageing studies show that diffusivity is differentially reduced for larger gas molecules, thus further enhancing their size-selectivity. [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]

A hydrophobic polymer of intrinsic microporosity (PIM-EA-TB) is employed to stabilize an organogel/aqueous electrolyte phase boundary based on an organic water-insoluble 4-(3-phenylpropyl)-pyridine phase. The organogel with electrocatalytic metal complexes embedded is immobilized on glassy carbon or on transparent mesoporous tin-doped indium oxide (ITO) electrodes. Liquid/liquid ion transfer voltammetry is investigated for a 4-(3-phenylpropyl)-pyridine organogel/aqueous electrolyte interface for two types of redox systems: tetraphenylporphyrinato-Mn(III/II) (MnTPP) and phthalocyanato-Mn(III/II) (MnPc). Electron transfer is shown to be coupled to reversible liquid/liquid anion transfer processes for PF6−, ClO4−, SCN−, and NO3−, with a change in mechanism for the more hydrophilic anions Cl−, F−, and SO42−. In situ UV-Vis spectroelectrochemistry reveals reversible Mn(III/II) redox processes coupled to ion transfer for MnTPP. But further complexity and a detrimental side reaction are observed for MnPc causing gradual loss of the electrochemical response in the presence of dioxygen. [ABSTRACT FROM AUTHOR]

Hydrogen oxidation and oxygen reduction are two crucial energy conversion reactions, which are shown to be both strongly affected by the presence of intrinsically microporous polymer coatings on electrodes. Polymers of intrinsic microporosity (PIMs) are known to possess extremely high internal surface area and ability to bind gases under dry conditions. It is shown here that both, hydrogen‐ and oxygen gas binding into PIMs, also occurs under wet or "triphasic" conditions in aqueous electrolyte environments (when immersed in 0.01 M phosphate buffer at pH 7). For two known PIM materials (PIM‐1 and PIM‐PY), nanoparticles are formed by an anti‐solvent precipitation protocol and then cast as a film onto platinum or glassy carbon electrodes. Voltammetry experiments reveal evidence for hydrogen and oxygen binding. Both, PIM‐1 and PIM‐PY, locally store hydrogen or oxygen gas at the electrode surface and thereby significantly affect electrocatalytic reactivity. The onset of oxygen reduction on glassy carbon is shifted by 0.15 V in the positive direction. One for three: Due to their hydrophobic and molecularly rigid nature, intrinsically microporous polymers affect the conditions for gas|liquid electrolyte|solid electrode triphasic reactions. [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 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]

Membranes composed of Polymers of Intrinsic Microporosity (SBF-PIMs) have potential for commercial gas separation. Here we report a combined simulation and experimental study to investigate the effect on polymer microporosity and gas permeability by placing simple substituents such as methyl, t-butyl and fused benzo groups onto PIMs derived from spirobifluorene (PIM-SBFs). It is shown that methyl or t-butyl substituents both cause a large increase in gas permeabilities with four methyl groups enhancing the concentration of ultramicropores (＜0.7 nm), which contribute to selective gas transport. The t-butyl substituents lower selectivity by generating a greater concentration of larger, less selective, micropores (＞1.0 nm). Long-term ageing studies (＞3.5 years) demonstrate the potential of PIM-SBFs as high-performance membrane materials for gas separations. In particular, the data for the PIM derived from tetramethyl substituted SBF reaches the proposed 2015 Robeson upper bound for O2/N2 and, hence, hold promise for the oxygen or nitrogen enrichment of air. Mixed gas permeation measurements for CO2/CH4 of the aged PIM-SBFs also demonstrate their potential for natural gas or biogas upgrading. [ABSTRACT FROM AUTHOR]

Polymers of intrinsic microporosity (PIMs) have been identified as potential next generation membrane materials for the separation of gas mixtures of industrial and environmental relevance. Based on the exceptionally rigid methanopentacene (MP) structural unit, a Polymer of Intrinsic Microporosity (PIM-MP-TB) was designed to demonstrate high selectivity for gas separations. PIM-MP-TB was prepared using a polymerisation reaction involving the formation of Tröger's base linking groups and demonstrated an apparent BET surface area of 743 m2 g−1 as a powder. The microporosity of PIM-MP-TB was also characterized by chain packing simulations. PIM-MP-TB proved soluble in chlorinated solvents and was cast as a robust, free-standing film suitable for gas permeation measurements. Despite lower gas permeability as compared to previously reported PIMs, high selectivities for industrially relevant gas pairs were obtained, surpassing the 2008 Robeson upper bound for H2/CH4 and O2/N2, (e.g., PO2 = 999 Barrer; αO2/N2 = 5.0) and demonstrating a clear link between polymer rigidity and selectivity. Upon aging, the permeability data move parallel to the Robeson upper bounds with a decrease of permeability, compensated by a related increase in selectivity. Mixed gas permeation measurement for CO2/CH4 and CO2/N2 mixtures confirmed the excellent selectivity of PIM-MP-TB for potentially relevant separations such as biogas upgrading and CO2 capture from flue gas. Importantly, unlike other high performing PIMs, PIM-MP-TB is prepared in four simple steps from a cheap starting material. [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]

Polymers of intrinsic microporosity (PIMs) are a class of porous organic polymer (POP) that form microporous solids due to the inefficient packing of their rigid and contorted macromolecular chains. In contrast to other types of POP, PIMs are not comprised of a network of cross-linked covalent bonds so that they can be dissolved in organic solvents and processed into robust films, coatings or fibres. Here, over twelve years' accumulated research on the synthesis of PIMs is reviewed. To date, three types of polymerisation reaction have been used successfully to prepare PIMs of sufficient molecular mass to form robust self-standing films. These involve the formation of dibenzodioxin, Tröger's base and imide linkages between monomeric units. This rapid development of synthetic methods for preparing PIMs has been driven by their rich potential for numerous diverse applications and this synergistic relationship between synthesis and functionality is set to continue. [ABSTRACT FROM AUTHOR]

Silver microparticles (ca. 1 μm average size clustered into cage-like aggregates of 10-20 μm diameter) are shown to adhere to a glassy carbon electrode surface to give voltammetric current responses, which are considerably enhanced/stabilised when applying a coating with a molecularly rigid polymer of intrinsic microporosity (PIM-EA-TB). In preliminary voltammetric experiments characteristic Ag(0/I) surface oxidation and back-reduction processes are observed in aqueous phosphate buffer (associated with silver phosphate layer formation on the silver surface). In contrast to the oxidation, which is dominated by a nucleation process causing a sharp well-defined current signal, for the back-reduction stochastic current responses are observed possibly associated with density fluctuations in the surrounding liquid phase ('Brownian activation') as an essential part of the mechanism of conversion of surface-oxidised silver back to silver metal. [ABSTRACT FROM AUTHOR]

Polymers of intrinsic microporosity (PIM or here PIM-EA-TB) offer a highly rigid host environment into which hexachloroplatinate(IV) anions are readily adsorbed and vacuum carbonised (at 500 °C) to form active embedded platinum nanoparticles. This process is characterised by electron and optical microscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and electrochemical methods, which reveal that the PIM microporosity facilitates the assembly of nanoparticles of typically 1.0 to 2.5-nm diameter. It is demonstrated that the resulting carbonised 'Pt@cPIM' from drop-cast films of ca. 550-nm average thickness, when prepared on tin-doped indium oxide (ITO), contain not only fully encapsulated but also fully active platinum nanoparticles in an electrically conducting hetero-carbon host. Alternatively, for thinner films (50-250 nm) prepared by spin coating, the particles become more exposed due to additional loss of the carbon host. In contrast to catalyst materials prepared by vacuum-thermolysed hexachloroplatinate(IV) precursor, the platinum nanoparticles within Pt@cPIM retain high surface area, electrochemical activity and high catalyst efficiency due to the molecular rigidity of the host. Data are presented for oxygen reduction, methanol oxidation and glucose oxidation, and in all cases, the high catalyst surface area is linked to excellent catalyst utilisation. Robust transparent platinum-coated electrodes are obtained with reactivity equivalent to bare platinum but with only 1 μg Pt cm (i.e. ~100% active Pt nanoparticle surface is maintained in the carbonised microporous host). [ABSTRACT FROM AUTHOR]