- Metal-doped bipyridine linked covalent organic framework films as a platform for photoelectrocatalysts
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The development of efficient photoenergy conversion systems is highly demanded from the viewpoint of solving energy and environmental problems. Covalent organic frameworks (COFs) have attracted much attention as novel photofunctional materials because of their wide-range visible-light absorption, which is related to their large π-conjugation systems. The other important property of COFs is their ability to support a wide variety of metals via coordinate bonds; metal-doped COFs exhibit various electron-transfer catalytic activities depending on the metal species. Here, we newly synthesized free-standing metal-doped COF films as photoelectrocatalysts and evaluated the photoelectrochemical oxygen reduction reaction (ORR) properties of Cu atoms doped in a COF. The photocurrent corresponding to the ORR started to increase under 670 nm irradiation, and the photocurrent for the Cu-doped COF was five times larger than that for the COF without Cu. The action spectra, fluorescence spectra, and in situ X-ray absorption spectra indicate that the electrons photoexcited in the COF were transferred to oxygen via the Cu atoms. Thus, the Cu atoms coordinated to the COF serve as active catalytic sites for the photoinduced ORR. This journal is
- Harada, Takashi,Hosokawa, Tomoya,Iwase, Kazuyuki,Kamiya, Kazuhide,Nakanishi, Shuji,Tsuchida, Kosei,Tsuji, Masaki
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- Covalent Organic Frameworks Enabling Site Isolation of Viologen-Derived Electron-Transfer Mediators for Stable Photocatalytic Hydrogen Evolution
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Electron transfer is the rate-limiting step in photocatalytic water splitting. Viologen and its derivatives are able to act as electron-transfer mediators (ETMs) to facilitate the rapid electron transfer from photosensitizers to active sites. Nevertheless, the electron-transfer ability often suffers from the formation of a stable dipole structure through the coupling between cationic-radical-containing viologen-derived ETMs, by which the electron-transfer process becomes restricted. Herein, cyclic diquats, a kind of viologen-derived ETM, are integrated into a 2,2′-bipyridine-based covalent organic framework (COF) through a post-quaternization reaction. The content and distribution of embedded diquat-ETMs are elaborately controlled, leading to the favorable site-isolated arrangement. The resulting materials integrate the photosensitizing units and ETMs into one system, exhibiting the enhanced hydrogen evolution rate (34600 μmol h?1 g?1) and sustained performances when compared to a single-module COF and a COF/ETM mixture. The integration strategy applied in a 2D COF platform promotes the consecutive electron transfer in photochemical processes through the multi-component cooperation.
- Mi, Zhen,Zhou, Ting,Weng, Weijun,Unruangsri, Junjuda,Hu, Ke,Yang, Wuli,Wang, Changchun,Zhang, Kai A. I.,Guo, Jia
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supporting information
p. 9642 - 9649
(2021/03/16)
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- Nickel(ii)-modified covalent-organic framework film for electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF)
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Electrochemical oxidation of 5-hydroxymethylfurfural (HMF) is a promising synthetic route for 2,5-furandicarboxylic acid (FDCA) production. Here, we prepared a nickel(ii)-modified covalent-organic framework (COF) film TpBpy-Ni@FTO for HMF electrooxidation. With a high conversion of HMF (96%), TpBpy-Ni@FTO afforded a 58% FDCA yield. This work underlines the great potential of COF-based materials in electrocatalysis.
- Cai, Meng,Ding, Sha,Gibbons, Bradley,Yang, Xiaozhou,Kessinger, Matthew C.,Morris, Amanda J.
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supporting information
p. 14361 - 14364
(2020/12/01)
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- Flexibility Matters: Cooperative Active Sites in Covalent Organic Framework and Threaded Ionic Polymer
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The combination of two or more reactive centers working in concert on a substrate to facilitate the reaction is now considered state of the art in catalysis, yet there still remains a tremendous challenge. Few heterogeneous systems of this sort have been exploited, as the active sites spatially separated within the rigid framework are usually difficult to cooperate. It is now shown that this roadblock can be surpassed. The underlying principle of the strategy presented here is the integration of catalytic components with excellent flexibility and porous heterogeneous catalysts, as demonstrated by the placement of linear ionic polymers in close proximity to surface Lewis acid active sites anchored on the walls of a covalent organic framework (COF). Using the cycloaddition of the epoxides and CO2 as a model reaction, dramatic activity improvements have been achieved for the composite catalysts in relation to the individual catalytic component. Furthermore, they also clearly outperform the benchmark catalytic systems formed by the combination of the molecular organocatalysts and heterogeneous Lewis acid catalysts, while affording additional recyclability. The extraordinary flexibility and enriched concentration of the catalytically active moieties on linear polymers facilitate the concerted catalysis, thus leading to superior catalytic performance. This work therefore uncovers an entirely new strategy for designing bifunctional catalysts with double-activation behavior and opens a new avenue in the design of multicapable systems that mimic biocatalysis.
- Sun, Qi,Aguila, Briana,Perman, Jason,Nguyen, Nicholas,Ma, Shengqian
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supporting information
p. 15790 - 15796
(2016/12/16)
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- 5,5′-diamino-2,2′-bipyridine: A versatile building block for the synthesis of bipyridine/catechol ligands that form homo- and heteronuclear helicates
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Herein we present an improved synthesis of 5,5′-diamino-2,2′- bipyridine (1) starting from the pyrrole-protected aminopyridine 4. By standard reactions 1 can easily be transformed into the imine- or amide-bridged dicatechol-bipyridine ligands L1/sup
- Albrecht, Markus,Janser, Ingo,Luetzen, Arne,Hapke, Marko,Froehlich, Roland,Weis, Patrick
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p. 5742 - 5748
(2007/10/03)
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- Synthesis of 5-substituted 2,2′-bipyridines from substituted 2-chloropyridines by a modified Negishi cross-coupling reaction
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A new and practical approach to a number of differently 5-substituted 2,2′-bipyridines starting from substituted 2-chloropyridines has been found through the application of modified Negishi cross-coupling conditions. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Luetzen, Arne,Hapke, Marko
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p. 2292 - 2297
(2007/10/03)
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