Microporous Polymer Networks Research Articles

Melamine-based microporous polymer for highly efficient removal of copper(II) from aqueous solution

In this study, we investigated the ability of a melamine-based microporous polymer network as an adsorbent for removal of copper(II) species from aqueous solutions. A designed Schiff based network (SNW) with high specific surface area was synthesized using melamine and terephthalaldehyde monomers at 180 °C for 3 days followed by a freeze-drying process. The porous structure of the material was confirmed by SEM analysis and CO2 adsorption/desorption studies at 77.3 K. The adsorption character of the SNW polymer for various metal salts, namely Pb(II), Fe(II), Hg(II), Zn(II), Ni(II) and Cd(II), was investigated and a specific sorption behaviour against Cu(II) salts was observed. The role of pH and contact time was examined and the highest adsorption capacity for Cu(II) was found as 92% with pH 3.5 at the end of 300 min. As evidenced by XRD and Fourier transform infrared spectral analysis, the sorption mechanism is attributed to the coordination system formed between amino groups in the porous structure and Cu(II) ions. Reusability of the system was also demonstrated by applying four cycles without any significant loss of activity. © 2016 Society of Chemical Industry

Electrochemically Generated Thin Films of Microporous Polymer Networks: Synthesis, Properties, and Applications

Electrochemical oxidative polymerization of rigid, multifunctional monomers allows for the synthesis of microporous thin films with high surface areas. Multifunctional, carbazole‐ and thiophene‐based rigid monomers have been utilized as rigid 3D building blocks (tectons) toward microporous polymer films with relatively smooth surface morphology. Within the last four years, several studies following this approach have been published that report interesting results on the application of these electrogenerated films in organic electronics, photoluminescence‐based or electrochemical chemodetectors, electrochemical supercapacitors, and light‐harvesting antennae for exciton pumping. In this work, the synthetic approaches for the electrochemical polymerization of multifunctional carbazole‐ and thiophene‐based tectons as well as resulting properties and application possibilities of the electrogenerated microporous polymer films are reviewed. image

Copper(II) removal from the aqueous solution using microporous benzidine-based adsorbent material

In this work, the ability of benzidine-based microporous polymer network as adsorbent for removal of copper(II) species from aqueous solutions was investigated. The designed benzidine-based adsorbent material (BBAM) with high specific surface area was synthesized using phloroglucinol and benzidine monomers with hydrochloric acid catalyst at 180°C for 3 days followed by freeze–drying process. The porosity character of the material was confirmed by SEM analysis and CO2 adsorption/desorption studies at 0°C. The adsorption efficiency of the BBAM for different metal ions, namely Hg(II), Fe(II), Pb(II), Ni(II), Zn(II) and Cd(II) was experimented, however, a specific sorption behavior against Cu(II) ions was observed. The function of pH and contact time was studied and the highest adsorption capacities for Cu(II) were found as 97% with pH of 4.5 at the end of 300min. As verified by FTIR and XRD spectral analysis, the sorption mechanism is attributed to the coordination system formed between amino groups in the porous structure and Cu(II) ions. Reusability of the system was also presented by applying six cycles without any significant loss of activity.

Conjugated microporous polymer networks with adjustable microstructures for high CO2 uptake capacity and selectivity.

A series of phenylene-based conjugated microporous polymers (CMPs) of the A6 + Mx (x = 2, 3, 4, 6) type were synthesized. By tuning the monomer length and geometry, the BET surface area of CMPs can be tuned from 571 to 1115 m2 g-1. Amongst the synthesized CMPs, A6CMP-1 exhibits the highest CO2 adsorption capacity of 1218 mg g-1 at 318 K and 60 bar pressure. In addition, A6CMP-4 shows a high selectivity ratio of 47 for CO2/N2.

Microporous Polymer Networks Made by Cyclotrimerization of Commercial, Aromatic Diisocyanates.

The cyclotrimerization of commercial, aromatic diisocyanates allows for the formation of monolithic, microporous polymer networks with SBET surface areas up to 1300-1500 m2/g. The process has been up-scaled for production of 100 g batches. The monolithic materials show a promising potential for the removal of lipophilic components from aqueous mixtures.

Thiophene-Based Microporous Polymer Networks via Chemical or Electrochemical Oxidative Coupling

Four thiophene-based monomers have been synthesized by Stille- or Suzuki-type couplings followed by chemical or electrochemical polymerization into microporous polymer networks (MPNs) with high BET surface areas (SBET). Similar SBET values of up to 2020 and 2135 m2 g–1 have been determined for tetraphenylmethane-cored bulk MPN powders and thin films, respectively. Electrochemical polymerization in boron trifluoride diethyl etherate (BFEE)/dichloromethane (DCM) mixtures allows for the generation of MPN films with optimized porosity. Moreover, an interesting effect of boron trifluoride on the connectivity of the monomeric units during electropolymerization is observed for 3-thienyl-based monomers. Finally, the electrochemical reduction of 1,3,5-trinitrobenzene at MPN-modified glassy carbon (GC) electrodes shows increased cathodic responses compared to nonmodified GC electrodes due to interaction between electron-deficient nitroaromatic analyte and electron-rich MPN film. The influence of the specific surfac...

Conjugated Microporous Poly(Benzochalcogenadiazole)s for Photocatalytic Oxidative Coupling of Amines under Visible Light.

Metal-free visible-light photocatalysts offer a clean, sustainable solution to many pressing environmental issues. Herein, we present a molecular design strategy to fine-tune the valence and conduction band levels of a series of conjugated microporous polymer networks based on poly(benzochalcogenadiazole) for heterogeneous photocatalysis. Enhanced photocatalytic efficiency was observed by altering the chalcogene moieties in the electron-accepting benzochalcogenadiazole unit of the polymer backbone structure. Photooxidative coupling of benzylamines was chosen as a model reaction. This design strategy leading to enhanced efficiency could potentially improve a wide range of photoredox reactions.

Electrogenerated thin films of microporous polymer networks with remarkably increased electrochemical response to nitroaromatic analytes.

Thin films of microporous polymer networks (MPNs) have been generated by electrochemical polymerization of a series of multifunctional carbazole-based monomers. The microporous films show high Brunauer-Emmett-Teller (BET) surface areas up to 1300 m2 g(-1) as directly measured by krypton sorption experiments. A correlation between the number of polymerizable carbazole units of the monomer and the resulting surface area is observed. Electrochemical sensing experiments with 1,3,5-trinitrobenzene as prototypical nitroaromatic analyte demonstrate an up to 180 times increased current response of MPN-modified glassy carbon electrodes in relation to the nonmodified electrode. The phenomenon probably involves intermolecular interactions between the electron-poor nitroaromatic analytes and the electron-rich, high surface area microporous deposits, with the electrochemical reduction at the MPN-modified electrodes being an adsorption-controlled process for low scan rates. We expect a high application potential of such MPN-modified electrodes for boosting the sensitivity of electrochemical sensor devices.

Melamine‐Based Microporous Network Polymer Supported Palladium Nanoparticles: A Stable and Efficient Catalyst for the Sonogashira Coupling Reaction in Water

AbstractA template consisting of a melamine‐based microporous polymer network was synthesized and utilized as a solid support to stabilize palladium nanoparticles; the resulting Pd/SNW1 material showed good catalytic activity in copper‐free Sonogashira coupling in water. Various aryl iodides were efficiently coupled with arylacetylenes under very low catalyst loadings in an environmentally benign medium. Hot filtration tests confirmed the heterogeneity of the catalyst, which was reused under the optimized conditions without any significant change in its activity. This simple preparation of the catalyst, the stability of the catalyst, product selectivity, and easy recovery and regeneration indicate the possible utilization of this catalytic system in a multitude of catalyzed reactions and industrial processes.

Microporous polymer network films covalently bound to gold electrodes.

Covalent attachment of a microporous polymer network (MPN) on a gold surface is presented. A functional bromophenyl-based self-assembled monolayer (SAM) formed on the gold surface acts as co-monomer in the polymerisation of the MPN yielding homogeneous and robust coatings. Covalent binding of the films to the electrode is confirmed by SEIRAS measurements.

Microporous, tetraarylethylene-based polymer networks generated in a reductive polyolefination process

Highly fluorescent microporous polymer networks with triazine cores have been prepared and tested for their PL quenching response to arylamines.

One-step synthesis of a cyclic 2,17-dioxo[3,3](4,4') biphenylophane and first preparation of a microporous polymer network from a macrocyclic precursor by cyclotrimerization.

One-step synthesis of a cyclic 2,17-dioxo[3,3](4,4')biphenylophane (MC) was achieved in high yield; its structure was verified by single crystal X-ray analysis. As a first example, a microporous polymer network was formed from macrocycle MC via acid-catalysed cyclotrimerization yielding a BET surface area of ca. 570 m(2) g(-1).

Molecular template-directed synthesis of microporous polymer networks for highly selective CO2 capture.

Porous polymer networks have great potential in various applications including carbon capture. However, complex monomers and/or expensive catalysts are commonly used for their synthesis, which makes the process complicated, costly, and hard to scale up. Herein, we develop a molecular template strategy to fabricate new porous polymer networks by a simple nucleophilic substitution reaction of two low-cost monomers (i.e., chloromethylbenzene and ethylene diamine). The polymerization reactions can take place under mild conditions in the absence of any catalysts. The resultant materials are interconnected with secondary amines and show well-defined micropores due to the structure-directing role of solvent molecules. These properties make our materials highly efficient for selective CO2 capture, and unusually high CO2/N2 and CO2/CH4 selectivities are obtained. Furthermore, the adsorbents can be completely regenerated under mild conditions. Our materials may provide promising candidates for selective capture of CO2 from mixtures such as flue gas and natural gas.

Nafion-microporous organic polymer networks composite membranes

A series of new Nafion composite membranes have been prepared by the self-assembly of microporous organic polymer networks (MOPNs) and Nafion. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) reveal that MOPNs and Nafion membranes have good miscibility affording homogeneous composite membranes Nafion-MOPN-x. Compared with the recast Nafion membrane, Nafion-MOPN-x composite membranes show excellent thermal and mechanical properties, good dimensional stability, low methanol permeability, and proper proton conductivity. Also, the passive direct methanol fuel cell (DMFC) of Nafion-MOPN-3 membrane presents a maximum power density of 21.5mWcm−2 at 25°C. These results show the introduction of MOPNs can improve the interface compatibility and lessen the cavity problem between fillers and polymeric matrix during chemical blend. Therefore, it casts a new light on developing stable polymer electrolyte membranes (PEMs) for fuel cell application.

Hypercrosslinked microporous organic polymer networks derived from silole-containing building blocks

Three silole-containing hypercrosslinked microporous organic polymer networks were designed and synthesized via Friedel–Crafts alkylation promoted by anhydrous FeCl3. The results demonstrated that the substitution of methyl group connected with silicon atom by benzene has negligible effect on the surface area and gas uptake ability of the polymer networks. The network-1 produced from 1,1-dimethyl-2,3,4,5-tetraphenylsilole shows a surface area up to 1236 m2 g−1 with the hydrogen uptake ability of 1.33 wt% (77.3 K/1.13 bar) and a carbon dioxide capture capacity of 2.94 mmol g−1 at 273 K/1.13 bar. The isosteric heats of carbon dioxide sorption for all of the polymer networks exceed 25 kJ/mol at the zero coverage because the introduction of silicon atom into the polymer skeleton enhanced the binding affinity between the adsorbent and CO2 molecules. In addition, the selectivity of the polymer networks for CO2/N2 and CO2/CH4 were found to be around 35 and 6 at 273 K, respectively. These results show that these materials are potential candidates for applications in post-combustion CO2 capture and separation.

A tetrathiafulvalene (TTF)-conjugated microporous polymer network.

Conjugated microporous polymer networks have been prepared from the strong electron donor tetrathiafulvalene (TTF) and 1,3,5-triethynylbenzene (TEB) by using the Sonogashira-Hagihara cross-coupling reaction. Optimization of reaction conditions yields polymers with surface areas of up to 434 m(2) g(-1) . The strong electron-donating properties of the network can be proven by iodine exposure. Structural and electronic changes due to formation of the charge-transfer salt from TTFs in the porous network and iodine within the pores are investigated.

Heterogeneous organocatalysts composed of microporous polymer networks assembled by Tröger's base formation

Microporous polymer networks are assembled from triamino-triptycene monomers using a polymerisation reaction based on the formation of Troger's base (TB). The highly rigid triptycene units ensure that the polymer networks demonstrate significant intrinsic microporosity as demonstrated by apparent surface areas of up to 1000 m2 g−1. These networks act as heterogeneous basic catalysts which enhance greatly the rate of a model Knovenagel reaction between malonontrile and benzaldehyde. Indeed, the microporous networks, which possess a high concentration of basic sites, enhance the rate of the Knovenagel reaction even more efficiently than using Troger's base as a homogeneous catalyst.

Tuning porosity and activity of microporous polymer network organocatalysts by co-polymerisation

Microporous polymer networks based on binaphthyl phosphoric acids are suitable heterogeneous asymmetric organocatalysts. Herein we show that the porous characteristics of such networks can be fine-tuned by co-polymerisation. This enables us to investigate the influence of the surface area and porosity in microporous networks on their catalytic performance. In this case, the activity of the polymers in an asymmetric hydrogenation reaction is increased by the use of polymers with higher surface areas.

High surface area hypercrosslinked microporous organic polymer networks based on tetraphenylethylene for CO2 capture

A series of hypercrosslinked microporous organic copolymer networks was synthesized via Friedel–Crafts alkylation of tetraphenylethylene (TPE) and/or 1,1,2,2-tetraphenylethane-1,2-diol (TPD) promoted by anhydrous FeCl3.

Controllable synthesis of hierarchical mesoporous/microporous nitrogen-rich polymer networks for CO2 and Cr(vi) ion adsorption

A facile and scalable one-pot approach has been developed for the preparation of hierarchical meso- and microporous nitrogen-rich polymer networks by sol–gel polymerization of melamine, resorcinol and terephthaldehyde.