The choice of reaction solvent has a major influence on the surface area and pore volume in conjugated microporous polymer (CMP) networks synthesized by Sonogashira−Hagihara palladium-catalyzed cross-coupling chemistry of aromatic dibromo monomers with 1,3,5-triethynylbenzene. Four solvents were evaluated for these reactions: N,N-dimethylformamide (DMF), 1,4-dioxane, tetrahydrofuran (THF), and toluene. Networks synthesized in DMF tend to exhibit the highest surface areas (up to 1260 m2/g), whereas those synthesized in toluene have on average significantly lower surface areas and pore volumes. By judicious choice of reaction solvent, microporous materials can be prepared which combine high surface area with a variety of functional groups of interest in applications such as gas storage, molecular separations, and catalysis.
Conjugated microporous polymers (CMPs) are a class of materials with unique structural properties, including extended π-conjugation and permanent microporosity, with a huge synthetic diversity offering up a number of topological strategies for control of their amorphous structure and properties. This provides a platform for the exploration of chemical and electronic structure properties that is not available for other classes of materials. CMPs have applications in gas storage, gas separation, heterogeneous catalysis, chemosensors, light harvesting devices, polymer light emitting diodes and as supercapacitors. There is great potential for as yet undiscovered applications as we further explore their synthetic diversity and gain new strategies for controlling structure. In this chapter, we define the core chemical and structural properties of CMPs and the synthetic strategies adopted. We discuss the various methods of analysing and rationalising the CMP molecular structure and porous properties, the particular challenges in elucidating the structure of amorphous CMPs and strategies for tackling these challenges. Finally, we discuss limitations for CMP materials and future directions that might overcome these challenges and open up new areas for exploration.
A range of conjugated microporous polymer networks has been prepared using Sonogashira−Hagihara cross-coupling of 1,3,5-triethynylbenzene with a number of functionalized dibromobenzenes. Porous poly(arylene ethynylene) networks with surface areas up to 900 m2/g were produced. The surface chemistry of the networks was varied by monomer selection, thus allowing control over physical properties such as hydrophobicity. Additionally, it was shown that the dye sorption behavior of the networks can be controlled by varying the hydrophobicity. This expands significantly on the utility of this approach, allowing high surface area networks to be prepared with properties that can be tailored for applications such as catalysis and separations.
Low band-gap conjugated microporous polymers (CMPs) based on benzothiadiazole (BTZ) and thiophene-benzothiadiazole-thiophene (TBT) functional groups are prepared. The polymers show moderate surface areas and broad light absorption covering the whole visible light region. Fluorescence of one of the polymers can be readily quenched by the in situ blending of fullerene.
Conjugated microporous polymers (CMPs) are a class of materials with unique structural properties, including extended π-conjugation and permanent microporosity, with a huge synthetic diversity offering up a number of topological strategies for control of their amorphous structure and properties. This provides a platform for the exploration of chemical and electronic structure properties that is not available for other classes of materials. CMPs have applications in gas storage, gas separation, heterogeneous catalysis, chemosensors, light harvesting devices, polymer light emitting diodes and as supercapacitors. There is great potential for as yet undiscovered applications as we further explore their synthetic diversity and gain new strategies for controlling structure. In this chapter, we define the core chemical and structural properties of CMPs and the synthetic strategies adopted. We discuss the various methods of analysing and rationalising the CMP molecular structure and porous properties, the particular challenges in elucidating the structure of amorphous CMPs and strategies for tackling these challenges. Finally, we discuss limitations for CMP materials and future directions that might overcome these challenges and open up new areas for exploration.
<p>Water-dispersible porous polymeric dispersions (PPDs) have been synthesised by reversible addition-fragmentation chain transfer mediated polymerisation-induced self-assembly (RAFT-mediated PISA). The core-shell particles posses a microporous core formed from divinylbenzene and fumaronitrile while the outer polyethylene glycol shell enables the particles to be dispersible in a wide range of solvents. The PPD was shown to have a heirarchical structure of small primary nanoparticles within larger, well-defined aggregates of 220 nm as measured by electron microscopy and small angle x-ray scattering (SAXS) and exhibited a surface area of 274 m<sup>2</sup>/g. Furthermore these samples were found to be fluoresent and demonstrate selective detection of harmful nitroaramatics in solution with extremly low limits of detection, 169 ppb for picric acid, as well as possessing a CO<sub>2</sub> uptake of 1.1 mmol/g at 273 K.</p>
Functionalized hypercrosslinked polymers (HCPs) with surface areas between 213 and 1124 m2/g based on a range of monomers containing different chemical moieties were evaluated for CO2 capture using a pressure swing adsorption (PSA) methodology under humid conditions and elevated temperatures. The networks demonstrated rapid CO2 uptake reaching maximum uptakes in under 60 s. The most promising networks demonstrating the best selectivity and highest uptakes were applied to a pressure swing setup using simulated flue gas streams. The carbazole, triphenylmethanol and triphenylamine networks were found to be capable of converting a dilute CO2 stream (>20%) into a concentrated stream (>85%) after only two pressure swing cycles from 20 bar (adsorption) to 1 bar (desorption). This work demonstrates the ease with which readily synthesized functional porous materials can be successfully applied to a pressure swing methodology and used to separate CO2 from N2 from industrially applicable simulated gas streams under more realistic conditions.
Phosphate shortages and the ensuing pressures on food security have led to an interest in processed sewage sludge as a substitute for commercial fertilisers. The presence of heavy metals in this nutrient source causes concerns around environmental release and pollution. This work builds towards a resin-in-pulp sludge detoxification process. It showcases the kinetic and thermodynamic adsorption capabilities of the ion-exchange resins C107E (carboxylic acid functionality), MTS9301 (iminodiacetic acid) and TP214 (thiourea), with respect to Cu(II), Fe(II), Pb(II) and Zn(II), within a simulated sewage sludge weak acid (acetate) leachate. The isotherms produced in this complex system were quite different to those generated when single metals were investigated in isolation, with desorption of lower affinity species clearly observed at higher equilibrium concentration values. Mixed-metal isotherm data were fitted to common two-parameter isotherm models and also a novel modified Langmuir model, which better accounted for the effects of desorption and competition. Kinetic data were also fit to common two-parameter models; results suggesting the system was likely film diffusion-controlled and followed pseudo-2nd-order kinetics. C107E displayed rapid adsorption of lead (t1/2 = 26 ± 3min), and significant uptake of all metals. MTS9301 showed high affinity for copper ions, with concurrent desorption of all the other metals, and also displayed the fastest kinetics (t1/2 = 14.1 ± 0.9, 130 ± 20, 25 ± 5 and 49 ± 6 min for copper, iron(II), lead and zinc, respectively). C107E and MTS9301 showed far slower adsorption for iron(II) than the other three metals, which invited the possibility of kinetic separations. TP214 had reasonable effectiveness in removal of copper, but poor affinity for all other metals. The greatest difficulty in modelling the multi-metal system was the two-stage trends observed in equilibrium experiments, as metal-proton exchanges become metal-metal exchanges. While not having the highest capacity, MTS9301 was recommended as the most appropriate resin for rapid and efficient removal of Cu, Pb and Zn from the acetate medium.
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