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Covalent Organic Frameworks

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https://www.readbyqxmd.com/read/30516956/zig-zag-sp2-carbon-chains-passing-through-sp3-framework-a-driving-force-toward-room-temperature-ferromagnetic-graphene
#1
Jiří Tuček, Katerina Hola, Giorgio Zoppellaro, Piotr Blonski, Rostislav Langer, Miroslav Medved, Toma Susi, Michal Otyepka, Radek Zbořil
Stabilization of ferromagnetic ordering in graphene-based systems up to room temperature remains an important challenge owing to huge scope for applications in electronics, spintronics, biomedicine, and separation technologies. To date, several strategies have been proposed, including edge engineering, introduction of defects and dopants, and covalent functionalization. However, these techniques are usually hampered by limited temperature sustainability of ferromagnetic ordering. Here, we describe a method for the well-controlled sp3 functionalization of graphene to synthesize zig-zag conjugated sp2 carbon chains that can act as communication pathways among radical motifs...
December 5, 2018: ACS Nano
https://www.readbyqxmd.com/read/30512941/a-highly-ordered-nanoporous-two-dimensional-covalent-organic-framework-with-modifiable-pores-and-its-application-in-water-purification-and-ion-sieving
#2
Valerie Kuehl, Jiashi Yin, Phuoc Duong, Bruce Mastorovich, Brian S Newell, Katie Dongmei Li-Oakey, Bruce A Parkinson, John O Hoberg
The preparation of membranes with high selectivity based on specific chemical properties such as size and charge would impact the effi-ciency of the worlds energy supply, the production of clean water and many other separation technologies. We report a flexible synthetic protocol for preparing highly ordered two dimensional nanoporous polymeric materials (termed covalent organic frameworks or COFs) that allow for placing virtually any function group within the nanopores. We demonstrate that membranes, fabricated with this new fami-ly of materials with carboxylated pores, are very water permeable, as well highly charged and size selective...
December 4, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30511412/nylon-mof-composites-via-postsynthetic-polymerization
#3
Mark Kalaj, Michael Denny, Kyle Bentz, Joseph Palomba, Seth Mason Cohen
Hybridization of metal-organic frameworks (MOFs) and polymers into composites yields materials that display the exceptional properties of MOFs with the robustness of polymers. However, realization of MOF-polymer composites requires efficient dispersion and interactions of MOF particles with polymer matrices, which remains a significant challenge. Herein, we report a simple, scalable, bench-top approach to covalently tethered nylon-MOF polymer composite materials by an interfacial polymerization technique. The copolymerization of a modified UiO-66-NH2 MOF with a growing polyamide fiber (PA-66) during an interfacial polymerization gave hybrid materials with up to ~29 weight percent MOF...
December 3, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/30511056/amorphous-to-crystalline-transformation-toward-controllable-synthesis-of-fibrous-covalent-organic-frameworks-enabling-promotion-of-proton-transport
#4
Weifu Kong, Wei Jia, Rong Wang, Yifan Gong, Changchun Wang, Peiyi Wu, Jia Guo
Reversible imine exchange is adopted to molecularly re-arrange polyazomethine-based amorphous fibers into covalent organic frameworks (COFs) retaining pristine fibrous characters with periodic and oriented micropore channels. Such fibrous COFs can immobilize the assembled Nafion to form long-range proton conduction pathways, thus largely promoting proton transport.
December 4, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/30502198/a-dual-function-molecularly-imprinted-optopolymer-based-on-quantum-dots-grafted-covalent-organic-frameworks-for-the-sensitive-detection-of-tyramine-in-fermented-meat-products
#5
Dianwei Zhang, Huilin Liu, Weitao Geng, Yanping Wang
Molecular imprinting is a technique for polymerization using a template molecule to produce cavities in the polymer with high selectivity. The successful synthesis of a dual-function molecularly-imprinted optopolymer (MIOP) based on quantum dots-grafted covalent-organic frameworks as adsorbents has allowed the simultaneous detection of tyramine by optosensing and solid-phase extraction coupled with high performance liquid chromatography (SPE-HPLC). The MIOP, obtained by a one-pot reverse microemulsion polymerization, selectively measured tyramine from fermented meat products...
March 30, 2019: Food Chemistry
https://www.readbyqxmd.com/read/30499569/a-2-2-bipyridine-containing-covalent-organic-framework-bearing-rhenium-i-tricarbonyl-moieties-for-co-2-reduction
#6
Damir A Popov, John M Luna, Nicholas M Orchanian, Ralf Haiges, Courtney A Downes, Smaranda C Marinescu
The reduction of CO2 into higher energy products such as carbon-based fuels and feedstocks is an attractive strategy for mitigating the continuous rise in CO2 emissions associated with the growing global energy demand. Rhenium tricarbonyl complexes bearing 2,2'-bipyridine (2,2'-bpy) ligands are well-established molecular electrocatalysts for the selective reduction of CO2 to CO. Construction of efficient devices for this electrochemical process requires the immobilization of electrocatalysts to electrode surfaces...
November 30, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/30499568/on-the-impact-of-competing-intra-and-intermolecular-triplet-state-quenching-on-photobleaching-and-photoswitching-kinetics-of-organic-fluorophores
#7
Jochem H Smit, Jasper H M van der Velde, Jingyi Huang, Vanessa Trauschke, Sarah S Henrikus, Si Chen, Nikolaos Eleftheriadis, Eliza M Warszawik, Andreas Herrmann, Thorben Cordes
While buffer cocktails remain the most commonly used method for photostabilization and photoswitching of fluorescent markers, intramolecular triplet-state quenchers emerge as an alternative strategy to impart fluorophores with 'self-healing' or even functional properties such as photoswitching. In this contribution, we evaluated combinations of both approaches and show that inter- and intramolecular triplet-state quenching processes compete with each other. We find that although the rate of triplet-state quenching is additive, the photostability is limited by the faster pathway...
November 30, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/30497825/facile-synthesis-of-covalent-organic-framework-incorporated-electrospun-nanofiber-and-application-to-pipette-tip-solid-phase-extraction-of-sulfonamides-in-meat-samples
#8
Zhiming Yan, Biqing Hu, Qianlian Li, Sunxian Zhang, Jie Pang, Chunhua Wu
In this work, covalent organic frameworks SNW-1 incorporated polyacrylonitrile (SNW-1@PAN) nanofiber was synthesized and used as pipette tip solid phase extraction (PT-SPE) adsorbent for preconcentration of five sulfonamides (SAs) in meat samples. The SNW-1@PAN nanofiber was fabricated via two steps, including the hydrothermal synthesis of SNW-1 and co-electrospinning of the SNW-1/PAN mixture. The three dimensional networks of electrospun nanofiber provide both low backpressure and rapid mass transfer in PT-SPE application, thus preventing the problems of high backpressure and leakage caused by directly packing SNW-1 into PT-SPE cartridge...
November 22, 2018: Journal of Chromatography. A
https://www.readbyqxmd.com/read/30485740/covalent-organic-frameworks-chemistry-beyond-the-structure
#9
Sharath Kandambeth, Kaushik Dey, Rahul Banerjee
Covalent organic frameworks (COFs) represent a new field of rapidly growing chemical research which takes direct inspiration from diverse covalent bonds existing between atoms. The success of linking atoms in two and three dimensions to construct extended framework structures moved the chemistry of COFs beyond the structures to methodologies, highlighting the possibility of prospective applications. Although structure to property relation in COFs has led to fascinating properties, chemical stability, processability and scalability were some of the important challenges that needed to be overcome for their successful implementation...
November 28, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30485087/simulating-powder-x-ray-diffraction-patterns-of-two-dimensional-materials
#10
Yibin Jiang, Lingyun Cao, Xuefu Hu, Zikun Ren, Cankun Zhang, Cheng Wang
Powder X-ray diffraction (PXRD) is widely used to study atomic arrangements in ordered materials. The Bragg equation, which describes diffraction of a three-dimensional crystal, fails in two-dimensional (2D) cases. Complete integration of diffraction signals from a continuum instead of discrete directions in the Bragg equation is thus required for proper data interpretation of 2D materials. Furthermore, modeling of preferred orientation of the 2D crystals as well as geometric disorders are also of vital importance...
November 28, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/30484915/local-electronic-structure-of-molecular-heterojunctions-in-a-single-layer-2d-covalent-organic-framework
#11
Trinity Joshi, Chen Chen, Huifang Li, Christian S Diercks, Gaoqiang Wang, Peter J Waller, Hong Li, Jean-Luc Bredas, Omar M Yaghi, Michael F Crommie
The synthesis of a single-layer covalent organic framework (COF) with spatially modulated internal potentials provides new opportunities for manipulating the electronic structure of molecularly defined materials. Here, the fabrication and electronic characterization of COF-420: a single-layer porphyrin-based square-lattice COF containing a periodic array of oriented, type II electronic heterojunctions is reported. In contrast to previous donor-acceptor COFs, COF-420 is constructed from building blocks that yield identical cores upon reticulation, but that are bridged by electrically asymmetric linkers supporting oriented electronic dipoles...
November 28, 2018: Advanced Materials
https://www.readbyqxmd.com/read/30483681/facile-dual-doping-strategy-via-carbonization-of-covalent-organic-frameworks-to-prepare-hierarchically-porous-carbon-spheres-for-membrane-capacitive-deionization
#12
Yuquan Li, Xingtao Xu, Shujin Hou, Jiaqi Ma, Ting Lu, Jiachen Wang, Yefeng Yao, Likun Pan
For the first time, N,B dual-doped porous carbon spheres (denoted as PCSs) were prepared through direct carbonization of covalent organic frameworks (COFs) and used as an electrode material for membrane capacitive deionization (MCDI). Due to their high accessible surface area and defect-abundant structure offered by N,B-co-doping, the nanostructured PCSs exhibit high desalination ability and are expected to be promisingly applied in MCDI.
November 28, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/30480990/a-new-insight-into-the-anchoring-mechanism-of-polysulfides-inside-nanoporous-covalent-organic-frameworks-for-lithium-sulfur-batteries
#13
Xuedan Song, Mengru Zhang, Man Yao, Ce Hao, Jieshan Qiu
The application prospects of lithium-sulfur (Li-S) batteries are constrained by many challenges, especially the shuttle effect of lithium polysulfides (Li2 Sx ). Recently, microporous covalent organic framework (COF) materials have been used to anchor-electrodes in lithium-sulfur (Li-S) batteries, because of its preferable characteristics, such as self-design ability, suitable pore size and various active groups. In order to identify the ideal anchoring materials that can effectively restrain the shuttle of Li2 Sx species, the anchoring mechanism between COF materials and Li2 Sx species should be investigated in depth...
November 27, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/30465429/insights-into-high-conductivity-of-the-two-dimensional-iodine-oxidized-sp2-c-cof
#14
Qiuju Zhang, Mingzhi Dai, Hezhu Shao, Ziqi Tian, Yichao Lin, Liang Chen, Xiao Cheng Zeng
The conductivity of newly synthesized two-dimensional (2D) sp2-carbon-hybridized -conjugated covalent organic framework (sp2-c-COF) can be enhanced by as much as 12 orders of magnitude after iodine oxidation processing (Science, 2017, 357, 673-676). To understand the chemical mechanism underlying such a huge increase in conductivity due to iodine oxidation, we performed multi-scale computation for the iodine oxidized 2D COF. We find that the high conductivity can be attributed to both hole transfer and ion transfer owing to the presence of both anionic iodine trimer (I3-) with nearly-linear structure and COF cations in the 2D COF...
November 22, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/30461145/a-nitrogen-rich-2d-sp%C3%A2-carbon-linked-conjugated-polymer-framework-as-a-high-performance-cathode-for-lithium-ion-batteries
#15
Shunqi Xu, Gang Wang, Bishnu Prasad Biswal, Matthew Addicoat, Silvia Paasch, Wenbo Sheng, Xiaodong Zhuang, Eike Brunner, Thomas Heine, Reinhard Berger, Xinliang Feng
In this work, we report a novel two-dimensional (2D) sp² carbon-linked conjugated polymer framework (2D CCP-HATN) with a nitrogen-doped skeleton, a periodical dual-pore structure and high chemical stability. The chemical identity of the polymer backbone consisting of hexaazatrinaphthalene (HATN) and cyanovinylene units linked entirely by carbon-carbon double bonds is verified by FT-IR, Raman and solid-state 13C cross-polarization magic-angle spinning (CP-MAS) NMR spectroscopies. In stacked form, together with the imine-linked covalent organic framework analogue 2D C=N HATN, the interior framework architecture of the crystalline 2D CCP-HATN is unambiguously demonstrated by powder X-ray diffraction and N2 adsorption-desorption measurements...
November 21, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/30456404/phase-transformation-in-two-dimensional-covalent-organic-frameworks-under-compressive-loading
#16
Jin Zhang
As a new class of two-dimensional (2D) materials, 2D covalent organic frameworks (COFs) are proven to possess remarkable electronic and magnetic properties. However, their mechanical behaviours remain almost unexplored. In this work, taking the recently synthesised dimethylmethylene-bridged triphenylamine (DTPA) sheet as an example, we investigate the mechanical behaviours of 2D COFs based on molecular dynamics simulations together with density functional theory calculations. A novel phase transformation is observed in DTPA sheets when a relatively large in-plane compressive strain is applied to them...
November 28, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/30444238/encapsulating-mo-3-s-13-2-clusters-in-cationic-covalent-organic-frameworks-enhancing-stability-and-recyclability-by-converting-a-homogeneous-photocatalyst-to-a-heterogeneous-photocatalyst
#17
Yuan-Jie Cheng, Rui Wang, Shan Wang, Xiao-Juan Xi, Lu-Fang Ma, Shuang-Quan Zang
We encapsulated anionic [Mo3S13]2- clusters in cationic COFs (EB-COF) to obtain the novel composite photocatalytic material Mo3S13@EB-COF. Comprehensive studies indicated that the Mo3S13@EB-COF was the product of a successful conversion of a homogeneous to a heterogeneous catalyst, and exhibited excellent stability and recyclability as well as a remarkable photocatalytic hydrogen evolution rate of 13 215 μmol g-1 h-1 under visible-light irradiation over the course of 18 hours.
November 16, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/30433777/interfacial-engineering-in-metal-organic-framework-based-mixed-matrix-membranes-using-covalently-grafted-polyimide-brushes
#18
Hongliang Wang, Sanfeng He, Xuedi Qin, Conger Li, Tao Li
Good interfacial compatibility is the key to realize the full potential of metal-organic framework-based mix matrix membranes for gas separation. Here we report a new approach that uses polyimide brushes covalently grafted on the MOF surface to engineer the MOF-polymer interface. Benefiting from the strong brush-brush interaction, polyimide grafted MOF particles can form a stand-alone membrane at 88 wt% MOF loading without the addition of polymeric matrix. Compared to traditional mixed-matrix membranes, the modified membranes exhibit improved ductility up to 472%, reduced interfacial tearing phenomenon under shear force, decreased matrix chain mobility, and improved plasticization resistance against CO2...
November 15, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30431266/urea-linked-covalent-organic-frameworks
#19
Chenfei Zhao, Christian S Diercks, Chenhui Zhu, Nikita Hanikel, Xiaokun Pei, Omar M Yaghi
2D covalent organic frameworks (COFs) with flexible urea linkages have been synthesized by condensation of 1,3,5-triformylphloroglucinol (TFP) with 1,4-phenylenediurea (BDU) or 1,1'-(3,3'-dimethyl-[1,1'-biphenyl]-4,4'-diyl)diurea (DMBDU). The resulting COF-117 and COF-118 undergo reversible structural dynamics within their layers, in response to inclusion and removal of guest molecules, emanating from urea C-N bond rotation and interlayer hydrogen-bonding interactions. These compounds are the first urea-linked COFs, serving to expand the scope of reticular chemistry...
November 15, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30431253/highly-fluoro-substituted-covalent-organic-framework-and-its-application-in-lithium-sulfur-battery
#20
Degao Wang, Nuo Li, Yiming Hu, Shun Wan, Min Song, Guipeng Yu, Yinghua Jin, Weifeng Wei, Kai Han, Gui-Chao Kuang, Wei Zhang
We report the preparation of a highly fluoro-substituted crystalline covalent organic framework (COF) and its application as a cathode material in lithium sulfur battery (LSB) upon sulfur confinement. A sulfur-functionalized COF with high sulfur content (60 wt%) was obtained through physisorption of elemental sulfur and subsequent SNAr reaction of sulfur with aromatic fluorides on the COF backbone. After such physical and chemical confinement of sulfur through post-functionalization approach, the COF material still shows some structural order, allowing us to investigate the structure-property relationship of such COF materials in LSB application...
November 15, 2018: ACS Applied Materials & Interfaces
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