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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]

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]

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]

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]

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]

Greatly enhanced microporosity is obtained for the amorphous porous polymers produced from the AlCl3-mediated coupling of aromatic hydrocarbons by using dichloromethane as the reaction solvent. A polymer of average BET surface area = 2435 m2 g−1 was obtained reproducibly from 1,3,5-triphenylbenzene with the additional porosity being provided as ultramicroporosity as demonstrated by very high CO2 adsorption at 273 K/1 bar. [ABSTRACT FROM AUTHOR]

We describe ion current rectification using a Polymer of Intrinsic Microporosity (PIM) based on Tröger's base (PIM-EA-TB). When deposited asymmetrically over one (or more) 20 μm diameter hole(s) in 6 μm thick poly(ethylene terephthalate) and investigated in a two-compartment electrochemical cell with acidified aqueous NaCl on both sides, novel ionic diode effects are observed. [ABSTRACT FROM AUTHOR]

Porosity in polymers of intrinsic microporosity (PIMs) is closely related to free volume: it arises from a chain structure combining rigid segments with sites of contortion, producing a large concentration of interconnected pores smaller than 1 nm. Membranes of these polymers are subject to physical aging, which decreases their permeability and reduces their performance in gas separation. In this work, a robust interpretation of PIM X-ray scattering features is developed with support from molecular dynamics simulations. The sensitivity of scattering patterns to time, temperature and film thickness is shown to be qualitatively consistent with physical aging, demonstrating that these high-free-volume, porous polymeric glasses present a unique opportunity to study structural changes during physical aging using scattering methods. Quantitative modeling of PIM scattering patterns remains challenging, and the time resolution required to capture the initial aging stages of a single film is difficult to achieve with laboratory instruments. However, the spectrum of glassy states accessed by varying film thickness and aging temperature raises the possibility that there may be two distinct mechanisms of aging in PIMs. [ABSTRACT FROM AUTHOR]

A highly gas permeable polyimide with improved molecular sieving properties isproducedbyusinga bisanhydride monomer based on the rigid ethanoanthracene unit. The polymer (PIM-PI-EA) demonstrates enhanced selectivity for gas separations so that its gas permeability data lie above the 2008 Robeson upper bounds for the important O2 -- N2, H2 -- N2, CO2 -- CH4 and CO2 -- N2 gas pairs. [ABSTRACT FROM AUTHOR]

Polymers of intrinsic microporosity (PIMs) are a promising alternative in gas separation applications; however, their industrial applicability is greatly reduced by their susceptibility toward sorption-induced plasticization. In this study, the effects of swelling during nitrogen adsorption isotherms at 77 K for five PIMs (PIM-1, PIM-1c, PIM-SBF, PIM-SBF-Me, and sPIM-1) were examined through predictive molecular simulations. The structural changes and adsorptive implications of swelling each PIM from 0 to 15% were analyzed by generating swollen “snapshots” of the PIM during the swelling process by means of an effective swelling procedure. The size of the free volume elements increased with the simulated swelling percentage, while the closely packed polymer chains remained associated. By comparing the simulated swollen and available experimental isotherms, this investigation shows that the amount of swelling observed during low-temperature nitrogen adsorption is strongly correlated with the interaction strength of the polymer matrix. Therefore, this study provides further support that PIMs should be designed with functionalities to increase the associative interactions of adjacent polymer chains while simultaneously prohibiting efficient packing to construct a gas separation membrane with limited low-temperature N2 swelling and high free volumes. [ABSTRACT FROM AUTHOR]

Predictive molecular simulations were utilized to screen an array of microporous organic solids in order to provide insight into important design principles for increasing porosity in these types of materials. The computational screening considered 22 organic molecules of intrinsic microporosity (OMIMs) incorporating varying core and end-group geometries. The simulations were validated for a subset of experimentally synthesized biphenyl-core OMIMs by excellent agreement with X-ray scattering data. Analysis of the simulations revealed the role of three structural design aspects for increasing porosity in these types of materials: (i) molecular rigidity, (ii) bulky end groups, and (iii) three-dimensionality. In particular, the porosity increased with molecular rigidity, and ideal simulations of rigid-body molecules resulted in surface areas larger by an order of magnitude. Increasing the bulkiness of the end groups, such as by the addition of awkward tert-butyl and adamantyl functional groups, also encouraged a more inefficient packing. Lastly, molecular shapes that were more three dimensional, instead of planar, provided greater porosity. While these design principles were examined here for OMIMs, they extend to similar classes of discrete organic materials, as well as microporous polymers. [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]

A blue light mediated photochemical process using solid graphitic carbon nitride (g-C 3 N 4 ) in ambient air/isopropanol vapour is suggested to be linked to "nanophase" water inclusions and is shown to produce approx. 50 μmol H 2 O 2 per gram of g-C 3 N 4 , which can be stored in the solid g-C 3 N 4 for later release for applications, for example, in disinfection or anti-bacterial surfaces.

Polymers of intrinsic microporosity (PIMs) are a promising alternative in gas separation applications; however, their industrial applicability is greatly reduced by their susceptibility toward sorption-induced plasticization. In this study, the effects of swelling during nitrogen adsorption isotherms at 77 K for five PIMs (PIM-1, PIM-1c, PIM-SBF, PIM-SBF-Me, and sPIM-1) were examined through predictive molecular simulations. The structural changes and adsorptive implications of swelling each PIM from 0 to 15% were analyzed by generating swollen "snapshots" of the PIM during the swelling process by means of an effective swelling procedure. The size of the free volume elements increased with the simulated swelling percentage, while the closely packed polymer chains remained associated. By comparing the simulated swollen and available experimental isotherms, this investigation shows that the amount of swelling observed during low-temperature nitrogen adsorption is strongly correlated with the interaction strength of the polymer matrix. Therefore, this study provides further support that PIMs should be designed with functionalities to increase the associative interactions of adjacent polymer chains while simultaneously prohibiting efficient packing to construct a gas separation membrane with limited low-temperature N2 swelling and high free volumes.

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.

Microporous materials can be derived directly from soluble polymers whose randomly contorted shapes prevent an efficient packing of the macromolecules in the solid state.

Network polymers exhibiting large surfaces areas (450-950 m2 g-1) are prepared by the phthalocyanine-forming reaction of a bis(phthalonitrile) monomer containing a rigid spirocyclic linking group.