Conjugated microporous polymer

Last updated

Conjugated microporous polymers (CMPs) are a sub-class of porous materials that are related to structures such as zeolites, metal-organic frameworks, and covalent organic frameworks, but are amorphous in nature, rather than crystalline. CMPs are also a sub-class of conjugated polymers and possess many of the same properties such as conductivity, mechanical rigidity, and insolubility. CMPs are created through the linking of building blocks in a π-conjugated fashion and possess 3-D networks. [1] Conjugation extends through the system of CMPs and lends conductive properties to CMPs. Building blocks of CMPs are attractive in that the blocks possess broad diversity in the π units that can be used and allow for tuning and optimization of the skeleton and subsequently the properties of CMPs. Most building blocks have rigid components such as alkynes that cause the microporosity. [1] CMPs have applications in gas storage, heterogeneous catalysis, light emitting, light harvesting, and electric energy storage. [2]

Contents

CMP showing rigid alkynes and aromatic rings Conjugated Microporous Polymer.png
CMP showing rigid alkynes and aromatic rings

Design and synthesis

Building blocks that make up the network of CMPs must contain an aromatic system and have at least two reactive groups. To generate the porous structure of CMPs, cross-coupling of building blocks with different geometries to create a 3-D polymer backbone is necessary, while self-condensation reactions occur in the homo-coupling of building blocks with similar geometry. [2] Geometries of building blocks are based on their point group. C2, C3, C4, C6 are the geometries seen for building blocks of CMPs.

Suzuki coupling

Since 1979, Suzuki coupling has been an efficient method for aryl-aryl bond formation. [3] The reaction conditions of Suzuki coupling for the formation of a biphenyl repeat unit for CMPs include the palladium catalyzed cross-coupling of an organo-boron reagent with an organic halide or sulfonate in the presence of some base. An advantage of using this method to synthesize CMPs is that reaction conditions are mild, there is commercial availability of organo-boron reagents, and the reaction has high functional group tolerance. This method is best used for large scale synthesis of CMPs. [4] A drawback to Suzuki coupling is the reaction being oxygen sensitive, often leading to side products, as well as the reaction needing to be degassed. [2]

Suzuki Coupling CMPs.png

Sonogashira coupling

Sonogashira cross-coupling of aryl halides and alkynl groups occur with a palladium-copper co-catalyst in the presence of a base. A co-catalyst of palladium-copper is used in the coupling due to the improved reactivity that is achieved. [5] Sonogashira coupling reactions are advantageous in that the reaction has technical simplicity as well as functional group compatibility. CMPs are easily formed using this method due to the ease of rotation of alkynes in planar monomers to achieve a 3-D network. [6] The strength of these planar monomers can be tuned to control the pore diameters of CMPs. [7] Solvents in the Sonogashira coupling reaction can also play a role in the formation of CMPs. Solvents that facilitate the synthesis of CMPs best are dimethylformamide,1,4-dioxane, and tetrahydrofuran. [2] These solvents help neutralize the formation of the hydrogen halide produced as a byproduct. A disadvantage of using terminal alkynes as a monomer, is that terminal alkynes readily undergo homocoupling under the presence of oxygen, so the reaction must be carried out without the presence of oxygen and water. [8]

Sonogashira Coupling CMPs.png

Yamamoto coupling

In Yamamoto coupling, carbon-carbon bonds of aryl halogenide compounds are formed via mediation from a transition metal catalyst, most commonly bis(cyclooctadiene)nickel(0), often written as Ni(cod)2. An advantage to Yamamoto coupling is only a single halogen functionalized monomer is required, leading to diversity in monomer species, as well as a simple reaction procedure. While most research in CMPs focus on controlling pore size and surface area, the lack of flexibility in the monomers used in Yamamoto couplings give way to free volumes and porosity in CMPs. [9] Only recently have controlled pore size and surface area CMPs via Yamamoto coupling been reported. [2] Ifzan et al also recently reported contra-prepositionally substituted [6]CMP using Yamamoto coupling reaction. [10]

Yamamoto Coupling CMPs.png

Schiff base reaction

Most of the approaches currently used to synthesize CMPs must be carried out under anhydrous and oxygen-free environments due to the presence of metal catalysts. Due to the use of metal catalysts, polymers inevitably have trace metals present. [11] Reactions, such as the Schiff base reaction, have garnered much attention in that the reactions are metal free. In Schiff base, amine based monomers and aldehyde containing monomers undergo a reaction to create the repeat unit for CMPs. Schiff base is a preferred metal free method due to industrial scale cheap monomers containing multiple aldehyde functional groups. Another benefit of Schiff base is nitrogen is produced in creating CMPs, which could be beneficial for many applications. [12]

Schiff Base Reaction CMPs.png

Cyano cyclotrimerization

Cyano cyclotrimerization reactions occur under ionothermal conditions, where CMPs are obtained in molten zinc chloride at high temperatures. [13] Building units can produce C3N3 rings. These rings are then linked to a triangular plane as a secondary building unit. Cyclotrimerization is often used to link tetrahedral monomers to create CMPs. CMPs that are synthesized via cyano cyclotrimerization exhibit narrow micropore size distribution, high enthalpies of H2 adsorption and fast selective gas adsorption. [14]

Cyano Cyclotrimerization CMPs.png

Properties

Several physical properties of CMPs can be attributed to their extended conjugation or microporosity.

Electrical properties

Much like conductive metals, conjugated polymers exhibit electronic bands. The electrons of the conjugated system occupy the valence band and removal of electrons from this band or addition of electrons to the higher energy conductive band can lead to conductivity. [15] Conjugated materials can in many cases absorb visible light because of their delocalized π-system. These properties have led to applications in organic electronics and organic photonics. [16]

Physical properties

CMPs exhibit a high level of tunability with respect to surface area and pore size. Monomers can be designed with longer rigid moieties to increase surface area. The series of CMP-1,4 to CMP-5 shows a dramatic increase in surface area from 500 m2/g to 1000 m2/g. The increase in surface area can drastically improve their ability to be filled with various organic and inorganic compounds for different applications. The increased surface area can also improve gas sorption capabilities.

Series of extended linker CMPs CMPseries.png
Series of extended linker CMPs

A main drawback of CMPs is their inherent insolubility. This insolubility is cause by the long rigid moieties of the monomers. Several efforts have been made to increase solubility by the addition of solubilizing side-chains but this still remains a barrier to broad applications.

Applications

CMPs have been investigated for several applications since their discovery. Surface areas in CMPs can exceed 1000 m2/g in many cases, although related porous aromatic frameworks, [17] which lack extended conjugation, can have much higher surface areas of more than 5500 m2/g. The porosity of these materials has led to their evaluation as sorbents. Recent work has focused on their potential in terms of catalysis, [18] [19] [20] for example in the form of 'metal-organic CMPs', [21] and also for light harvesting, [22] and supercapacitors [23] taking advantage of their highly conjugated nature. A further advantage claimed for CMP materials is the ability to derivatize them with a wide range of functional groups. [19] [24]

CMPs have several been applied in several areas that take advantage of both their electronic properties and porous nature. Pores can be filled with inorganic materials, such as TiO2, for applications in photovoltaics. [25] They can be processed to serve as electronic junctions. They allow flow in and out of the pores that can be utilized for surface electrochemical applications.

Related Research Articles

Organolithium reagent

Organolithium reagents are organometallic compounds that contain carbon–lithium bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom to the substrates in synthetic steps, through nucleophilic addition or simple deprotonation. Organolithium reagents are used in industry as an initiator for anionic polymerization, which leads to the production of various elastomers. They have also been applied in asymmetric synthesis in the pharmaceutical industry. Due to the large difference in electronegativity between the carbon atom and the lithium atom, the C−Li bond is highly ionic. Owing to the polar nature of the C−Li bond, organolithium reagents are good nucleophiles and strong bases. For laboratory organic synthesis, many organolithium reagents are commercially available in solution form. These reagents are highly reactive, and are sometimes pyrophoric.

The Heck reaction is the chemical reaction of an unsaturated halide with an alkene in the presence of a base and a palladium catalyst to form a substituted alkene. It is named after Tsutomu Mizoroki and Richard F. Heck. Heck was awarded the 2010 Nobel Prize in Chemistry, which he shared with Ei-ichi Negishi and Akira Suzuki, for the discovery and development of this reaction. This reaction was the first example of a carbon-carbon bond-forming reaction that followed a Pd(0)/Pd(II) catalytic cycle, the same catalytic cycle that is seen in other Pd(0)-catalyzed cross-coupling reactions. The Heck reaction is a way to substitute alkenes.

The Suzuki reaction is an organic reaction, classified as a cross-coupling reaction, where the coupling partners are a boronic acid and an organohalide and the catalyst is a palladium(0) complex. It was first published in 1979 by Akira Suzuki, and he shared the 2010 Nobel Prize in Chemistry with Richard F. Heck and Ei-ichi Negishi for their contribution to the discovery and development of palladium-catalyzed cross-couplings in organic synthesis. This reaction is also known as the Suzuki–Miyaura reaction or simply as the Suzuki coupling. It is widely used to synthesize polyolefins, styrenes, and substituted biphenyls. Several reviews have been published describing advancements and the development of the Suzuki reaction. The general scheme for the Suzuki reaction is shown below, where a carbon-carbon single bond is formed by coupling an organoboron species (R1-BY2) with a halide (R2-X) using a palladium catalyst and a base.

The Sonogashira reaction is a cross-coupling reaction used in organic synthesis to form carbon–carbon bonds. It employs a palladium catalyst as well as copper co-catalyst to form a carbon–carbon bond between a terminal alkyne and an aryl or vinyl halide.

<i>N</i>,<i>N</i>-Diisopropylethylamine Chemical compound

N,N-Diisopropylethylamine, or Hünig's base, is an organic compound and an amine. It is named after the German chemist Siegfried Hünig. It is used in organic chemistry as a base. It is commonly abbreviated as DIPEA,DIEA, or i-Pr2NEt.

A dendralene is a discrete acyclic cross-conjugated polyene. The simplest dendralene is buta-1,3-diene (1) or [2]dendralene followed by [3]dendralene (2), [4]dendralene (3) and [5]dendralene (4) and so forth. [2]dendralene (butadiene) is the only one not cross-conjugated.

Pentacene Chemical compound

Pentacene is a polycyclic aromatic hydrocarbon consisting of five linearly-fused benzene rings. This highly conjugated compound is an organic semiconductor. The compound generates excitons upon absorption of ultra-violet (UV) or visible light; this makes it very sensitive to oxidation. For this reason, this compound, which is a purple powder, slowly degrades upon exposure to air and light.

Coordination polymer Polymer consisting of repeating units of a coordination complex

A coordination polymer is an inorganic or organometallic polymer structure containing metal cation centers linked by ligands. More formally a coordination polymer is a coordination compound with repeating coordination entities extending in 1, 2, or 3 dimensions.

Nanoporous materials

Nanoporous materials consist of a regular organic or inorganic bulk phase in which a porous structure is present. Nanoporous materials exhibit pore diameters that are most appropriately quantified using units of nanometers. The diameter of pores in nanoporous materials is thus typically 100 nanometers or smaller. Pores may be open or closed, and pore connectivity and void fraction vary considerably, as with other porous materials. Open pores are pores that connect to the surface of the material whereas closed pores are pockets of void space within a bulk material. Open pores are useful for molecular separation techniques, adsorption, and catalysis studies. Closed pores are mainly used in thermal insulators and for structural applications.

[n]Radialenes are alicyclic organic compounds containing n cross-conjugated exocyclic double bonds. The double bonds are commonly alkene groups but those with a carbonyl (C=O) group are also called radialenes. For some members the unsubstituted parent radialenes are elusive but many substituted derivatives are known.

Metal–organic framework

Metal–organic frameworks (MOFs) are a class of compounds consisting of metal ions or clusters coordinated to organic ligands to form one-, two-, or three-dimensional structures. They are a subclass of coordination polymers, with the special feature that they are often porous. The organic ligands included are sometimes referred to as "struts" or "linkers", one example being 1,4-benzenedicarboxylic acid (BDC).

Covalent organic frameworks (COFs) are a class of materials that form two- or three- dimensional structures through reactions between organic precursors resulting in strong, covalent bonds to afford porous, stable, and crystalline materials. COFs emerged as a field from the overarching domain of organic materials as researchers optimized both synthetic control and precursor selection. These improvements to coordination chemistry enabled non-porous and amorphous organic materials such as organic polymers to advance into the construction of porous, crystalline materials with rigid structures that granted exceptional material stability in a wide range of solvents and conditions. Through the development of reticular chemistry, precise synthetic control was achieved and resulted in ordered, nano-porous structures with highly preferential structural orientation and properties which could be synergistically enhanced and amplified. With judicious selection of COF secondary building units (SBUs), or precursors, the final structure could be predetermined, and modified with exceptional control enabling fine-tuning of emergent properties. This level of control facilitates the COF material to be designed, synthesized, and utilized in various applications, many times with metrics on scale or surpassing that of the current state-of-the-art approaches.

Mesoporous organosilica are a type of silica containing organic groups that give rise to mesoporosity. They exhibit pore size ranging from 2 nm - 50 nm, depending on the organic substituents. In contrast, zeolites exhibit pore sizes less than a nanometer. PMOs have potential applications as catalysts, adsorbents, trapping agents, drug delivery agents, stationary phases in chromatography and chemical sensors.

Two-dimensional polymer

A two-dimensional polymer (2DP) is a sheet-like monomolecular macromolecule consisting of laterally connected repeat units with end groups along all edges. This recent definition of 2DP is based on Hermann Staudinger's polymer concept from the 1920s. According to this, covalent long chain molecules ("Makromoleküle") do exist and are composed of a sequence of linearly connected repeat units and end groups at both termini.

Kim Kimoon

Kim Kimoon is a South Korean chemist and professor in the Department of Chemistry at Pohang University of Science and Technology (POSTECH). He is the first and current director of the Center for Self-assembly and Complexity at the Institute for Basic Science. Kim has authored or coauthored 300 papers which have been cited more than 30,000 times and he holds a number of patents. His work has been published in Nature, Nature Chemistry, Angewandte Chemie, and JACS, among others. He has been a Clarivate Analytics Highly Cited Researcher in the field of chemistry in 2014, 2015, 2016.

Pentacyanocyclopentadiene Chemical compound

Pentacyanocyclopentadiene is a derivative of cyclopentadiene with five cyano groups with the molecular formula C5H(CN)5. The corresponding anion, pentacyanocyclopentadienide, is a ligand with the molecular formula C
5(CN)−
5. In contrast to other anions based on a C5 ring unit it binds to metals through the pendant cyano groups rather than the C5 ring. The anion was first synthesised by Webster in the 1960s and its conjugate acid much later on. More recently Wright has discovered its extensive coordination chemistry. By virtue of a combination of mesomeric and aromatic stabilization of its anion, pentacyanocyclopentadiene is a superacid, with an estimated aqueous pKa of −11. The free acid was prepared by Reed in 2004 and was assigned a polymeric structure with protons that bridge planar C5(CN)5 units.

Montréalone

Montréalone is a mesoionic heterocyclic chemical compound.

Irshad Hussain Pakistani Scientist

Irshad Hussain is a Pakistani Scientist in the field of chemistry and among the few pioneers to initiate nanomaterials research in Pakistan.

Polymers of intrinsic microporosity (PIMs) are a unique class of microporous material developed by research efforts led by Neil McKeown, Peter Budd, et al. PIMs contain a continuous network of interconnected intermolecular voids less than 2 nm in width. Classified as a porous organic polymer, PIMs generate porosity from their rigid and contorted macromolecular chains that do not efficiently pack in the solid state. PIMs are composed of a fused ring sequences interrupted by Spiro-centers or other sites of contortion along the backbone. Due to their fused ring structure PIMs cannot rotate freely along the polymer backbone, ensuring the macromolecular components conformation cannot rearrange and ensuring the highly contorted shape is fixed during synthesis.

Conductive metal-organic frameworks

Conductive MOFs are a class of metal−organic frameworks with intrinsic ability of electronic conduction. Metal ions and organic linker self-assemble to form a framework which can be 1D/2D/3D in connectivity. In 2009, the first conductive MOF was described. This MOF Cu[Cu(pdt)2] (pdt=2,3-pyrazinedithiol) exhibited electrical conductivity of 6 × 10−4 S cm−1 at 300 K.

References

  1. 1 2 Xu Y, Jin S, Xu H, Nagai A, Jiang D (October 2013). "Conjugated microporous polymers: design, synthesis and application". Chem Soc Rev. 42 (20): 8012–31. doi:10.1039/c3cs60160a. PMID   23846024.
  2. 1 2 3 4 5 Liu, Q.; Tang Z.; Wu M.; Zhou Z. (2014). "Design, preparation, and application of conjugated microporous polymers". Polymer International. 63 (3): 381–392. doi:10.1002/pi.4640.
  3. ↑ Miyaura, N.; Yamada K.; Suzuki A. (1979). "A new stereospecific cross-coupling by the palladium-catalyzed reaction of 1-alkenylboranes with 1-alkenyl or 1-alkynyl halides". Tetrahedron Lett. 20 (36): 3437. doi:10.1016/s0040-4039(01)95429-2. hdl: 2115/44006 .
  4. ↑ Chen, L.; Honsho Y.; Seki S.; Jiang D. (2010). "Light-harvesting conjugated microporous polymers: rapid and highly efficient flow of light energy with a porous polyphenylene framework as antenna". J Am Chem Soc. 132 (19): 6742–8. doi:10.1021/ja100327h. PMID   20218681.
  5. ↑ Doucet H, Hierso JC (2007). "Palladium-based catalytic systems for the synthesis of conjugated enynes by sonogashira reactions and related alkynylations". Angew. Chem. Int. Ed. Engl. 46 (6): 834–71. doi:10.1002/anie.200602761. PMID   17335070.
  6. ↑ Cooper AI (2009). "Conjugated Microporous Polymers". Advanced Materials. 21 (12): 1291–1295. doi:10.1002/adma.200801971. ISSN   0935-9648.
  7. ↑ Jiang, JX.; Su F.; Trewin A.; Wood CD.; Niu H.; Jones J.; et al. (2009). "Microporous Poly(tri(4-ethynylphenyl)amine) Networks: Synthesis, Properties, and Atomistic Simulation". Macromolecules. 42 (7): 2658–2666. Bibcode:2009MaMol..42.2658J. doi:10.1021/ma802625d.
  8. ↑ Kotora, M. (2002). Handbook of Organopalladium Chemistry for Organic Synthesis. New York: Wiley Interscience. p. 973. ISBN   978-0-471-31506-3.
  9. ↑ Roncali, J.; Leriche, P.; Cravino, A. (2007). "From One- to Three-Dimensional Organic Semiconductors: In Search of the Organic Silicon?". Advanced Materials. 19 (16): 2045–2060. doi:10.1002/adma.200700135. ISSN   0935-9648.
  10. ↑ Arshad, Ifzan; Saeed, Aamer; Channar, Pervaiz Ali; Shehzadi, Syeda Aaliya; Irfan, Rana Muhammad (2019-09-05). "Synthesis of a Contrapositionally Substituted Cyclohexa-meta-phenylene: A Ready-to-Use Precursor for Cyclohexa-meta-phenylene-Based Materials". Synlett. 30 (16): 1886–1890. doi:10.1055/s-0039-1690676. ISSN   0936-5214.
  11. ↑ Holst, James R.; Stöckel, Ev; Adams, Dave J.; Cooper, Andrew I. (2010). "High Surface Area Networks from Tetrahedral Monomers: Metal-Catalyzed Coupling, Thermal Polymerization, and "Click" Chemistry". Macromolecules. 43 (20): 8531–8538. Bibcode:2010MaMol..43.8531H. doi:10.1021/ma101677t. ISSN   0024-9297.
  12. ↑ Kaur N, Delcros JG, Imran J, Khaled A, Chehtane M, Tschammer N, Martin B, Phanstiel O (March 2008). "A comparison of chloroambucil- and xylene-containing polyamines leads to improved ligands for accessing the polyamine transport system". J. Med. Chem. 51 (5): 1393–401. doi:10.1021/jm070794t. PMID   18281932.
  13. ↑ Kuhn P, Antonietti M, Thomas A (2008). "Porous, covalent triazine-based frameworks prepared by ionothermal synthesis". Angew. Chem. Int. Ed. Engl. 47 (18): 3450–3. doi:10.1002/anie.200705710. PMID   18330878.
  14. ↑ McKeown, Neil B.; Gahnem, Bader; Msayib, Kadhum J.; Budd, Peter M.; Tattershall, Carin E.; Mahmood, Khalid; Tan, Siren; Book, David; Langmi, Henrietta W.; Walton, Allan (2006). "Towards Polymer-Based Hydrogen Storage Materials: Engineering Ultramicroporous Cavities within Polymers of Intrinsic Microporosity". Angewandte Chemie International Edition. 45 (11): 1804–1807. doi:10.1002/anie.200504241. ISSN   1433-7851. PMID   16470904.
  15. ↑ Inzelt, Gyorgy (2008). Conducting Polymers: A new era in electrochemistry. Monographs in Electrochemistry. Berlin, Heidelberg: Springer. doi:10.1007/978-3-540-75930-0. ISBN   9783540759300.
  16. ↑ Liu, Qingquan; Zhe Tang; Minda Wu; Zhihua Zhou (2014). "Design, preparation and application of conjugated microporous polymers". Polymer International. 63 (3): 381–392. doi:10.1002/pi.4640.
  17. ↑ Ben, T.; Ren, H; Ma, S. Q.; Cao, D. P.; Lan, J. H.; Jing, X. F.; Wang, W. C.; Xu, J; Deng, F; Simmons, J. M; Qiu, S. L; Zhu, G. S. (2009). "Targeted synthesis of a porous aromatic framework with high stability and exceptionally high surface area". Angew. Chem. Int. Ed. 48 (50): 9457–9460. doi:10.1002/anie.200904637. PMID   19921728.
  18. ↑ Zhang, K.; D. Kopetzki; P. Seeberger; M. Antonietti; F. Vilela (2013). "Surface area control and photocatalytic activity of conjugated microporous poly(benzothiadiazole) networks". Angewandte Chemie International Edition. 52 (5): 1432–1436. doi:10.1002/anie.201207163. PMID   23345129.
  19. 1 2 Urakami, Hiromitsu; K. Zhang; F. Vilela (2013). "Modification of conjugated microporous poly-benzothiadiazole for photosensitised singlet oxygen generation in water". Chemical Communications. 49 (23): 2353–2355. doi:10.1039/C3CC38956A. PMID   23407715. S2CID   23552285.
  20. ↑ Xie, Z. G.; Wang, C; deKrafft, K. E.; Lin, W. B. (2011). "Highly stable and porous cross-linked polymers for efficient photocatalysis". J. Am. Chem. Soc. 133 (7): 2056–2059. doi:10.1021/ja109166b. PMID   21275413.
  21. ↑ Jiang, J.-X.; C. Wang; A. Laybourn; T. Hasell; R. Clowes; Y. Z. Khimyak; J. L. Xiao; S. J. Higgins; D. J. Adams; A. I. Cooper (2011). "Metal-organic conjugated microporous polymers". Angew. Chem. Int. Ed. 50 (5): 1072–1075. doi:10.1002/anie.201005864. PMID   21268197.
  22. ↑ Chen, L.; Y. Honsho; S. Seki; D. L. Jiang (2010). "Light-harvesting conjugated microporous polymers: Rapid and highly efficient flow of light energy with a porous polyphenylene framework as antenna". J. Am. Chem. Soc. 132 (19): 6742–6748. doi:10.1021/ja100327h. PMID   20218681.
  23. ↑ Yan, K.; Y. Xu; Z. Guo; D. L. Jiang (2011). "Supercapacitive energy storage and electric power supply using an aza-fused π-conjugated microporous framework". Angew. Chem. Int. Ed. 50 (37): 8753–8757. doi:10.1002/anie.201103493. PMID   21842523.
  24. ↑ Dawson, R.; A. Laybourn; R. Clowes; Y. Z. Khimyak; D. J. Adams; A. I. Cooper (2009). "Functionalized conjugated microporous polymers". Macromolecules. 42 (22): 8809–8816. Bibcode:2009MaMol..42.8809D. doi:10.1021/ma901801s.
  25. ↑ Boucle, Johann; Ravirajan, Punniamoorthy; Nelson, Jenny (2007). "Hybrid polymer-metal oxide thin films for photovoltaic applications". Materials Chemistry. 17 (30): 3141–3153. doi:10.1039/b706547g.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.