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Abstract

Conjugated microporous polymers are synthesized through facile one-step direct arylation polymerization of a single monomer unit, 8,11-dibromodithieno[3,2-a:2′,3′-c]phenazine, without preactivation of C-H bonds using organometallic reagents. The resulting polymers exhibit hierarchical porous structures and a narrow bandgap of 1.5 eV.

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A novel strong electron-acceptor unit, 9,10-difluorodithieno[3,2-a:2',3'-c]phenazine (DTPz), is synthesized and applied in the design of two donor-acceptor type emitters displaying long-lived delayed emission. Using either 9,9-dimethyl-9,10-dihydroacridine (DMAC) or triisopropyl-substituted benzo[1,2-b:4,5-b']dithiophene (BDT-TIPS) as the donor component, push-pull type chromophores exhibiting charge-transfer emission are obtained and found to afford either thermally activated delayed fluorescence (TADF) for DMAC or room temperature phosphorescence (RTP) for BDT-TIPS.
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Direct arylation polymerization between derivatives of dibromodiketopyrrolopyrrole (DPP) and thienoisoindigo (TIIG) resulted in two π-conjugated copolymers with average molecular weights up to 24.0 kDa and bandgaps as low as 0.8 eV. The structural analysis of the obtained two polymers revealed well-defined alternating conjugation backbones without obvious structural defects. The introduction of hexyl-group in the β-position of thiophene rings in the DPP units not only reduces the bandgap of conjugated polymer compared to a similar polymer containing bare-thiophene flanked DPP but also affects polymer morphology in thin films. P-type charge-transport characteristics were observed for two polymers in organic field-effect transistors with comparable hole mobilities. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017
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Direct (hetero)arylation polymerization (DHAP) has recently been established as an environmentally benign method for the preparation of conjugated polymers. This synthetic tool features the formation of C-C bonds between halogenated (hetero)arenes and simple (hetero)arenes with active C-H bonds, thereby circumventing the preparation of organometallic derivatives and decreasing the overall production cost of conjugated polymers. Since its inception, selectivity and reactivity of DHAP procedures have been improved tremendously through the careful scrutinity of polymerization outcomes and the fine-tuning of reaction conditions. A broad range of monomers, from simple arenes to complex functionalized heteroarenes, can now be readily polymerized. The successful application of DHAP now leads to nearly defect-free conjugated polymers possessing comparable, if not slightly better, characteristics than their counterparts prepared using classical cross-coupling methods. This comprehensive review describes the mechanisms involved in this process from experimental and theoretical standpoints, presents an up-to-date compendium of materials obtained by this means, and exposes its current limitations and challenges.
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Direct arylation polymerization (DAP) enabled facile synthesis of a narrow bandgap donor–acceptor conjugated polymer (PDFBT-Th4) composed of alternating 5,6-difluoro-2,1,3-benzothiadiazole and alkyl-quaternarythiophene. The optimized reaction condition of DAP catalyzed with Pd(OAc)2/(o-MeOPh)3P/PivOH/K2CO3 in o-xylene led to the target polymer with a number-average molecular weight (Mn) of 14.6 kDa without noticeable homocoupling or β-branching defects. UV-vis absorption spectra of PDFBT-Th4 indicate strong interchain aggregation in films. While the C-H selectivity and the alternating polymer structure of PDFBT-Th4 synthesized via DAP are comparable to those of the same type polymers synthesized via Stille coupling, the batch of PDFBT-Th4 synthesized via optimal DAP, despite its lower Mn, showed higher hole mobility in field effect transistors and larger power conversion efficiency in organic solar cell devices. These results further demonstrate the promising potential of DAP for efficient synthesis of high-performance D-A conjugated polymers for broad optoelectronic applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.
Article
Organic π-conjugated small molecules and polymers, owing to their light-weight, solution-processibility, mechanical flexibility, and large synthetic variety for finely tunable structures and properties, are promising semiconducting materials for a new generation of optoelectronic devices such as light-emitting diodes (LEDs), field-effect transistors (FETs), photovoltaic devices and sensors. A vast library of π-conjugated systems have been synthesized through conventional tools of couplings (e.g. Suzuki coupling, Stille coupling) and have been used in the fabrication of organic optoelectronic devices. In recent years an emerging synthetic technique called direct C-H arylation has been extensively studied as a facile, atom-efficient and environmentally benign pathway for the synthesis of conjugated polymers and small molecules. C-C bond formation between two heteroaryls can be carried via the activation of C-H bonds in a transition-metal catalytic cycle, thereby overcoming additional pre-functionalization steps involving toxic reagents. Direct arylation has been applied to a broad range of monomers and its reaction conditions have been optimized to produce defect-free polymers as well as small molecules that exhibit performances comparable with those made from conventional reactions. In this review, we summarize the recent progress in synthesis of conjugated small molecules, linear polymers and porous polymers by direct C-H arylation. In particular, small molecules and linear polymers based on benzothiadiazole (BT), diketopyrrolopyrrole (DPP), napththalenediimide (NDI), isoindigo (IG), thienoisoindigo (TIIG) and thienothiadiazole (TTD) are discussed in detail. Device performances of some representative polymers synthesized via direct arylation polymerization (DAP) in FETs and bulk heterojunction solar cells are summarized. We finally discuss the present challenges and perspectives of DAP towards future “greener” and more industrially scalable synthesis of π-conjugated semiconducting polymers for a variety of applications.
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A narrow bandgap D-A conjugated polymer based on 5H-dithieno [3,2-b:2′,3'-d]pyran alternating with 5,6-difluoro-2,1,3-benzothiadiazole (denoted as PDFBT-alt-DTP) was synthesized via direct C-H arylation polymerization (DAP) as an atomically efficient protocol. The optimal reaction condition for the DAP gave the target polymers with moderate number-average molecular weights (Mn) using optimized catalytic condition of Pd2 (dba)3/(o-MeOPh)3P/PivOH/K2CO3 in o-xylene. UV-vis-NIR absorption spectra of the obtained polymers show the presence of aggregation and interchain interaction in thin films. ¹H-NMR spectroscopic analysis indicates good C-H selectivity corresponding to an alternating strong-donor-alt-strong-acceptor conjugated backbone. The hole mobility of the resulting polymers in a magnitude of 10⁻⁴ cm²V⁻¹s⁻¹ was reached in bottom-gate top-contact field-effect transistors fabricated and tested under ambient conditions.
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The direct arylation synthesis of π-conjugated network polymers (conjugated microporous polymers: CMP) containing fluoroarene and triazine moieties was successfully achieved. The direct arylation of 1,2,4,5-tetrafluorobenzene or 1,3,5-trifluorobenzene with a tribromoarene having a triazine core under two reaction conditions (Conditions a: in DMAc, Conditions b: in toluene) gave four types of CMPs (CMP1a, CMP1b, CMP2a and CMP2b). Brunauer-Emmett-Teller (BET) surface area of CMP2a and CMP2b was higher than that of CMP1a and CMP1b because of a higher number of branches. The solvents used for the direct arylation polycondensation thus strongly affected the structure of the resulting CMPs.
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Among the various molecular designs developed for the synthesis of conjugated polymers and small molecules for optoelectronic applications, the donor: acceptor (D-A) approach is the most widely explored method over the past decades. Through the covalent linkage of electron-rich and electron-deficient units, a plethora of medium-low band gap materials has been developed and tested in organic photovoltaic devices. In particular, the quinoxaline aromatic structure and its derivatives are among the most studied electron deficient aromatic units used in D-A structures. Quinoxaline based materials are endowed with characteristics that are useful for large scale production in real world applications, such as easy synthetic procedures and excellent stability in air. Moreover, the use of quinoxaline based polymers/small molecules in bulk heterojunction (BHJ) devices led to power conversion efficiencies over 9%. Considering the potential of quinoxaline based materials, this review gathers together quinoxaline based polymers and small molecules reported in the literature during the last 5 years, summarizing and discussing the structure-properties relationships for this class of organic semiconductors, aiming to serve as a background and to promote efforts for the further development of new quinoxaline derivatives with improved and advanced properties for future applications.
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Thienoisoindigo (TIIG) has emerged as an attractive building block for high-performance organic optoelectronic devices. Here we report the first synthesis of a series of π-conjugated TIIG-based small molecules and alternating copolymers via direct C–H arylation, which enables the efficient synthesis without use of flammable and toxic orgametallic reagents in fewer steps compared Suzuki and Stille coupling. The direct arylation coupling between TIIG and two respective mono-bromo aryl reactants clearly shows that the α-H is more reactive than the β-H in the thiophene unit of TIIG. The high regioselectivity of TIIG monomer warrants the successful synthesis of high-quality alternating copolymers with minimal structural defects. PTIIG-BT polymer synthesized via direct arylation polymerization (DAP) showed comparable molecular weight and hole mobility than the same polymer previously synthesized via Suzuki coupling. Moreover, the two new polymers (PTIIG-TF and PTIIG-2FBT) synthesized via DAP showed hole mobility up to 10−3 cm2 V−1 s−1 in FET devices fabricated and tested under ambient conditions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016
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We report the synthesis of well-defined poly(3,3⌄-didodecyl-2,2′:5′,2″:5″,2⌄-quaterthiophene) (PQT12) from a direct heteroarylation polymerization (DHAP) of 5-bromo-3,3⌄-didodecyl-2,2′:5′,2″:5″,2⌄-quaterthiophene (monomer A) and 5-bromo-3′,4″-didodecyl-2,2′:5′,2″:5″,2⌄-quaterthiophene (monomer B). Experiments with different catalysts, ligands, additives, and solvents have revealed that the utilization of Herrmann-Beller catalyst and P(o-NMe2Ph)3 can lead to selective thiophene-thiophene couplings. In this regard, solid-state optical and thermal measurements were particularly useful to detect the presence of β-branching and indicate that minor molecular defects can induce important changes within the supramolecular organization. We also highlight the fact that steric protection around unsubstituted β-positions of α-bromothiophene units is needed to obtain a good selectivity of the cross-couplings at the α-positions. This can be achieved by the presence of a substituent at an adjacent β-position or the utilization of a bulky acidic additive (i.e., neodecanoic acid) in the catalytic system. These synthetic procedures applied to both monomers have led to PQT12 samples showing essentially the same optical and thermal properties and are comparable to those observed with their analogues prepared from chemical oxidation or Stille coupling. (Chemical Equation Presented).
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The synthesis of an ambipolar π-conjugated copolymer consisting of alternating diketopyrrolopyrrole and tetrafluorobenzene via direct arylation polymerization (DAP) is reported. Two different combinations of monomers are investigated under various catalytic conditions for DAP. The target polymer obtained under an optimized catalytic condition shows minimal structural defects, a number-average molecular weight of 33.2 kDa, and balanced electron and hole mobility of 1 × 10(-2) cm(2) V(-1) S(-1) in the organic field-effect transistors fabricated and tested under ambient conditions.
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3D frameworks are important because of their potential to combine the advantageous properties of porous materials with those associated with polymers. A series of novel 3D aromatic frameworks are presented that incorporate the heterocycles thiophene, selenophene, and tellurophene. The specific surface area and pore width of frameworks depends on the element that is used to build the framework. Optoelectronic properties are element-dependent, with heavy atoms red-shifting the optical properties and decreasing the energy gap of the solid. The metalloid nature of tellurophene allows the properties of this material to be tuned based on its oxidation state, even as an insoluble solid. The incorporation of the optoelectronic active thiophene, selenophene, and tellurophene units and the effect that they have on properties was studied. A supercapcitor device was fabricated using these frameworks, showing that these 3D frameworks are promising for optoelectronic uses. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Photocatalytic hydrogen production from water offers an abundant, clean fuel source, but it is challenging to produce photocatalysts that use the solar spectrum effectively. Many hydrogen-evolving photocatalysts are active in the ultraviolet range, but ultraviolet light accounts only 3% of the energy available in the solar spectrum at ground level. Solid-state crystalline photocatalysts have light absorption profiles that are a discrete function of their crystalline phase, and that are not always tunable. Here, we prepare a series of amorphous, microporous organic polymers with exquisite synthetic control over the optical gap in the range 1.94-2.95 eV. Specific monomer compositions give polymers that are robust and effective photocatalysts for the evolution of hydrogen from water in the presence of a sacrificial electron donor, without the apparent need for an added metal co-catalyst. Remarkably, unlike other organic systems, the best performing polymer is only photoactive under visible rather than ultraviolet irradiation.
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Direct arylation (DA) is emerging as a highly promising method to construct inexpensive conjugated materials for large-area electronics from simple and environ-mentally benign building blocks. Here, we show that exclusive α-C−H selectivity is feasible in the DA of π-extended monomers having unsubstituted thiophene or furan units, leading to fully linear materials. Two new naphthalene diimide-based conjugated copolymersP(FuNDIFuF 4) and P(ThNDIThF 4), composed of naphthalene diimide (NDI), furan (Fu) or thiophene (Th), and tetrafluorobenzene (F 4)are synthesized. Insight into structure−function relationships is given by density functional theory (DFT) calculations and variety of experimental techniques, whereby the effect of the heteroatom on the optical, structural, and electronic properties is investigated. The use of furan (Fu) allows for enhanced solubilities, a smaller dihedral angle between NDI and Fu as a result of the smaller size of Fu, and a smaller π−π-stacking distance in the solid state. P(FuNDIFuF 4) also exhibits a more edge-on orientation compared to P(ThNDIThF 4). Despite these advantageous properties of P(FuNDIFuF 4), P(ThNDIThF 4) exhibits the highest electron mobility: ∼1.3 cm 2 /(V s), which is a factor of ∼3 greater than that of P(FuNDIFuF 4). The enhanced OFET performance of P(ThNDIThF 4) is explained by reduced orientational disorder and the formation of a terrace-like thin-film morphology.
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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.
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We review the design and use of microporous polymers for pre- and post-combustion capture of CO2. Microporous organic polymers are promising candidates for CO2 capture materials. They have good physicochemical stabilities and high surface areas. Ultrahigh-surface-area microporous organic polymers could find use in pre-combustion capture, while networks with lower surface areas but higher heats of sorption for CO2 might be more relevant for lower pressure, post-combustion capture. We discuss strategies for enhancing CO2 uptakes including increasing surface area, chemical functionalization to provide high-enthalpy binding sites and the potential for pore size tuning. © 2013 Society of Chemical Industry
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Donor–acceptor alternating copolymers with chlorine atoms on the backbone are synthesized via a straightforward Stille polycondensation. Thiophene and chlorine‐substituted 2,3‐diphenylquinoxaline are chosen as the donor and acceptor moieties, respectively. Compared with the corresponding non‐substituted and fluorine‐substituted analogues, which are also synthesized for systematical studies, the chlorine‐bearing copolymer exhibits the deepest lowest unoccupied molecular orbital (LUMO). The highest occupied molecular orbital (HOMO) level of the chlorine‐bearing copolymer can be modified by applying different donor moieties. Additionally, these chlorine‐bearing copolymers show low self‐absorption and large Stokes Shift. Conjugated polymers bearing chlorine atoms on the backbone are synthesized in a straightforward manner via Stille polycondensation. The chlorine‐bearing polymers exhibit deeper lowest unoccupied molecular orbital (LUMO) levels than non‐substituted and fluoride polymers because the chlorine atoms cause a localized LUMO. The highest occupied molecular orbital (HOMO) level of the chlorine‐bearing copolymers can be individually modified by applying different donor moieties.
Article
Considering the high reactivity of the C–H bonds in fluorobenzenes for direct arylation and special properties of fluorinated polymers, herein, synthesis of fluorinated porous organic polymers via direct C–H arylation polycondensation is explored. The obtained polymers (FPOP-1 and FPOP-2) are well characterized and show high porosities with Brunauer–Emmett–Teller specific surface area of above 1000 m2 g–1. Different pore size distribution (PSD) profiles of porous polymers can be obtained by selecting different core constructing monomers. FPOP-2 exhibits a relatively narrower PSD with the dominant pore size at about 0.63 nm, which is more suitable for adsorption of small gas molecules (H2, CO2, and CH4) than FPOP-1. As a porous fluorinated hydrophobic material, FPOP-2 possesses high adsorption ability for toluene (976 mg g–1 at saturated vapor pressure and room temperature) due to its high porosities and binding affinities between the guest molecules and the host network. The good sorption capacity of FPOP-2 for toluene makes it show potential applications in elimination of harmful small aromatic molecules in the environment.
Article
Porous organic polymers (POPs), a class of highly cross-linked, amorphous polymers possessing micropores, have recently emerged as a versatile platform for the deployment of catalysts. These materials can be divided into three major classes: POPs that incorporate rigid well-defined homogeneous catalysts as building blocks, POPs that can be modified post-synthesis, and POPs that encapsulate metal particles. This perspective article summarizes the recent developments in POP-based catalysis and outlines the potential of POPs as platforms of heterogeneous catalysts along with some of the challenges.
Article
A family of four poly(3-hexylthiophene) (P3HT) based copolymers containing 5, 10, 15, and 20% of 3-cyanothiophene (CNT) incorporated in a random fashion with a regioregular linkage pattern (P3HT-CNT) were successfully synthesized via direct arylation polymerization (DArP). Unique reaction conditions, previously reported for P3HT, were used, which employ very low loadings of Pd(OAc)2 as a catalyst and an inexpensive bulky carboxylic acid (neodecanoic acid) as an essential part of the palladium catalytic center. The chemical structures and optoelectronic properties of DArP P3HT-CNT polymers were found to be similar to those of previously investigated P3HT-CNT polymers synthesized via Stille polycondensation. All polymers are semicrystalline with high hole mobilities and UV–vis absorption profiles that resemble P3HT, while the polymer highest occupied molecular orbital (HOMO) level decreases with increasing content of cyanothiophene in both DArP and Stille P3HT-CNT polymers. In photovoltaic devices with a PC61BM acceptor, DArP P3HT-CNT copolymers showed slightly lower open-circuit voltages (Voc) than their Stille P3HT-CNT analogues but similar fill factors (FF) and significantly enhanced short-circuit current densities (Jsc), leading to overall power conversion efficiencies for the DArP polymers that rivaled or exceeded those of the Stille polymers. This work further emphasizes the generality and relevance of DArP for the synthesis of conjugated polymers for use in organic solar cells and the attractive simplicity and ease of synthesis of random conjugated polymers.
Article
Alternating conjugated polymers of ethylenedioxythiophene and fluorene are prepared using three different synthetic methods to investigate the effects of these synthetic methods on the purity, field-effect transistor (FET) performance, and organic photovoltaic (OPV) performance of the polymer. In this study, microwave-assisted direct arylation polycondensation is used to obtain a high-purity, high-molecular-weight (147 kDa) polymer. This pure polymer exhibits a high FET hole mobility of 1.2 × 10−3 cm2 V−1 s−1 and high OPV performance with a power conversion efficiency of 4%, even though the polymer forms an amorphous film, which absorbs in a limited region of the spectrum.
Article
We report here the synthesis of conjugated microporous polymers (CMPs) based on pyrene building units. The networks are both microporous and highly luminescent. The emission colour and resulting band gap can be fine tuned by introducing different comonomers and by varying the monomer distribution (statistical versus alternating). These materials might find applications in organic electronics, photocatalysis, optoelectronics, or in sensing technologies.
Article
The coupling of aryl halides with catalytically activated aryl C-H bondsprovides a desirable and atom-economical alternative to standard cross-coupling reactions for the construction of new C-C bonds. The reaction, termed direct (hetero)arylation, is believed to follow a base-assisted, concerted metalation-deprotonation (CMD) pathway. During this process, carboxylate or carbonate anions coordinate to the metal center, typically palladium, in situ and assist in the deprotonation transition state. Researchers have employed this methodology with numerous arenes and heteroarenes, including substituted benzenes, perfluorinated benzenes, and thiophenes. Thiophene substrates have demonstrated high reactivity toward C-H bond activation when appropriately substituted with electron-rich and/or electron-deficient groups. Because of the pervasive use of thiophenes in materials for organic electronics, researchers have used this chemistry to modularly prepare conjugated small molecules and, more recently, conjugated polymers. Although optimization of reaction conditions such as solvent system, phosphine ligand, carboxylate additives, temperature, and time is necessary for efficient C-H bond reactivity of each monomer, direct (hetero)arylation polymerization (DHAP) can afford high yielding polymeric materials with elevated molecular weights. The properties of these materials often rival those of polymers prepared by traditional methods. Moreover, DHAP provides a facile means for the synthesis of polymers that were previously inaccessible or difficult to prepare due to the instability of organometallic monomers. The major downfall of direct (hetero)arylation, however, is the lack of C-H bond selectivity, particularly for thiophene substrates, which can result in cross-linked material during polymerization reactions. Further fine-tuning of reaction conditions such as temperature and reaction time may suppress these unwanted side reactions. Alternatively, new monomers can be designed where other reactive bonds are blocked, either sterically or by substitution with unreactive alkyl or halogen groups. In this Account, we illustrate these methods and present examples of DHAP reactions that involve the preparation of common homopolymers used in organic electronics (P3HT, PEDOT, PProDOT), copolymers formed by activation of electron-rich (bithiophene, fused bithiophenes) and electron-deficient monomers (TPD, 1,2,4,5-tetrafluorobenzene, 2,2'-bithiazole). Our group is optimizing these reactions and developing ways to make DHAP a common atom-economical synthetic tool for polymer chemists.
Article
Conjugated microporous polymers (CMPs) with controlled specific surface area have been prepared through Sonogashira-Hagihara cross-coupling reactions in the presence of silica nanoparticles as templating agents. The CMPs act as heterogeneous photosensitizers for producing singlet oxygen in a continuous flow synthesis.
Article
A straightforward synthesis of the fused-aromatic dione benzo[1,2-b:6,5-b']dithiophene-4,5-dione (BDTD) has been developed. This fused-aromatic dione was subjected to various chemical transformations to generate diverse molecules with potential use in π-conjugated materials for organic electronics.
Article
The past decade has seen the development of microporous materials (i.e., materials containing pores of dimensions <2 nm) derived wholly from organic components. Here we review this nascent area with a particular emphasis on amorphous polymers that possess intrinsic microporosity (IM), which is defined as microporosity that arises directly from the shape and rigidity of component macromolecules. Although IM can be readily identified within soluble non-network polymers and oligomers, for network polymers it is harder to differentiate IM from template effects that are responsible for the microporosity within hyper-cross-linked networks. The numerous examples of microporous polymers assembled from rigid monomers by the formation of rigid linking groups are surveyed and their IM assessed. The potential applications of these materials are highlighted.
Article
Two flavors of π: Semiconducting π-conjugated polymers may open new opportunities for the fabrication of ecofriendly, inexpensive optoelectronic devices. These materials can be prepared by direct arylation polycondensation, a straightforward approach that generates little waste and no toxic by-products.
Article
Highly microporous element org. frameworks were synthesized by the Pd catalyzed Suzuki coupling reaction. The crosslinked polymers show sp. surface areas of up to 1380 m2/g with strong hydrophobic character. Thus, they are interesting for the adsorption of nonpolar substances. By variation of the org. linkers, the modular concept of the materials in analogy to the metal-org. frameworks is demonstrated. The polymeric materials have thermal stability up to 573 °K and show no decompn. in aq. environment, allowing excellent handling and processing. The polymers are accessible by a basic synthetic approach, and by their chem. and thermal stabilities they may provide adequate properties for applications in many fields, esp. in adsorptive sepn. processes and storage of nonpolar gases. [on SciFinder(R)]
Article
Porous organic polymers (POPs), a class of highly crosslinked amorphous polymers possessing nano-pores, have recently emerged as a versatile platform for the deployment of catalysts. The bottom-up approach for porous organic polymer synthesis provides the opportunity for the design of polymer frameworks with various functionalities, for their use as catalysts or ligands. This tutorial review focuses on the framework structures and functionalities of catalytic POPs. Their structural design, functional framework synthesis and catalytic reactions are discussed along with some of the challenges.
Article
This Review aims to give an overview of recent research in the area of porous, organic-inorganic and purely organic, functional materials. Possibilities for introducing organic groups that exhibit chemical and/or physical functions into porous materials will be described, with a focus on the incorporation of such functional groups as a supporting part of the pore walls. The number of organic groups in the network can be increased such that porous, purely organic materials are obtained. Pores for thought: This Review describes porous functional materials in which the organic groups act as a part of the pore wall. The focus is on functional mesoporous organosilicas as well as meso- and microporous polymers. The large number of functional groups in such porous materials allows, for example, a new approach to bridging the gap between homogeneous and heterogeneous catalysis.
Article
The microporosity of two microporous polymer networks is investigated in detail. Both networks are based on a central spirobifluorene motif but have different linker groups, namely, imide and thiophene units. The microporosity of the networks is based on the "polymers of intrinsic microporosity (PIM)" design strategy. Nitrogen, argon, and carbon dioxide were used as sorbates in order to analyze the microporosity in greater detail. The gas sorption data was analyzed with respect to important parameters such as specific surface area, pore volume, and pore size (distribution). It is shown that the results can be strongly model dependent and swelling effects have to be regarded. (129)Xe NMR was used as an independent technique for the estimation of the average pore size of the polymer networks. The results indicate that both networks are mainly ultramicroporous (pore sizes < 0.8 nm) in the dry state, which was not expected based on the molecular design. Phase separation and network defects might influence the overall network morphology strongly. Finally, the observed swelling indicates that this "soft" microporous matter might have a different micropore size in the solvent swollen/filled state that in the dry state.
Article
The design of hydrogen storage materials is one of the principal challenges that must be met before the development of a hydrogen economy. While hydrogen has a large specific energy, its volumetric energy density is so low as to require development of materials that can store and release it when needed. While much of the research on hydrogen storage focuses on metal hydrides, these materials are currently limited by slow kinetics and energy inefficiency. Nanostructured materials with high surface areas are actively being developed as another option. These materials avoid some of the kinetic and thermodynamic drawbacks of metal hydrides and other reactive methods of storing hydrogen. In this work, progress towards hydrogen storage with nanoporous materials in general and porous organic polymers in particular is critically reviewed. Mechanisms of formation for crosslinked polymers, hypercrosslinked polymers, polymers of intrinsic microporosity, and covalent organic frameworks are discussed. Strategies for controlling hydrogen storage capacity and adsorption enthalpy via manipulation of surface area, pore size, and pore volume are discussed in detail.
Article
This review covers the development and advances in transition-metal-catalyzed aryl-aryl bond formation by direct arylation as well as its application to the synthesis of important compounds including natural products, pharmaceuticals, catalyst ligands and materials. Studies focused on developing milder, lower temperature direct arylation reactions are discussed in addition to recent studies that focused on the fine-tuning of catalyst systems to allow for the use of more inexpensive and industrially attractive aryl chlorides. It is emphasized that these studies will help both synthetic and material chemicals a great deal, making direct arylation a valuable tool for diverse academic and industrial applications.
Article
Rigid wiry nets: Conjugated microporous polymer networks are formed by Sonogashira–Hagihara coupling. Although these materials are amorphous, the micropore size and surface area can be controlled by varying the length of the phenyleneethynylene struts (see picture; the network is shown in blue, and one 1,3,5‐substituted benzene node and three connected struts are highlighted with C gray and H white).
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