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287 results on '"Zhang, Kai A. I."'

1. Direct electron transfer in a covalent triazine framework for enhanced photocatalytic hydrogen evolution.

Author

Qian, Zhuangfei, Zhang, Hao, Wei, Wenxin, Zhao, Yan, and Zhang, Kai A. I.

Subjects
CHARGE exchange, CHARGE transfer, PHOTOSYSTEMS, HYDROGEN, SPINE, ELECTRON donors
Abstract

Inspired by the direct charge transfer in the natural photosystems, herein, we design covalent triazine frameworks (CTFs) with direct electron transfer by constructing the minimal amount of –donor–acceptor 1–acceptor 2– type moieties in the CTF backbone for photocatalytic hydrogen evolution. By introducing only 0.75% of the acceptor 2, the as-prepared CTF exhibited an enhanced hydrogen evolution rate of 3215 μmol g−1 h−1. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Triazine Frameworks for the Photocatalytic Selective Oxidation of Toluene.

Author

Li, Sizhe, Huber, Niklas, Huang, Wei, Wei, Wenxin, Landfester, Katharina, Ferguson, Calum T. J., Zhao, Yan, and Zhang, Kai A. I.

Subjects
PHOTOCATALYTIC oxidation, STRUCTURE-activity relationships, TRIAZINES, REACTIVE oxygen species, TOLUENE, DENSITY functional theory, PHOTOCATALYSTS
Abstract

Investigations into the selective oxidation of inert sp3 C−H bonds using polymer photocatalysts under mild conditions have been limited. Additionally, the structure‐activity relationship of photocatalysts often remains insufficiently explored. Here, a series of thiophene‐based covalent triazine frameworks (CTFs) are used for the efficient and selective oxidation of hydrocarbons to aldehydes or ketones under ambient aerobic conditions. Spectroscopic methods conducted in situ and density functional theory (DFT) calculations revealed that the sulfur atoms within the thiophene units play a pivotal role as oxidation sites due to the generation of photogenerated holes. The effect of photogenerated holes on photocatalytic toluene oxidation was investigated by varying the length of the spacer in a CTF donor‐acceptor based photocatalyst. Furthermore, the manipulation of reactive oxygen species was employed to enhance selectivity by weakening the peroxidative capacity. As an illustrative example, this study successfully demonstrated the synthesis of a precursor of the neurological drug AMG‐579 using a photocatalytic protocol. [ABSTRACT FROM AUTHOR]

Published
2024
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17. Emerging covalent triazine framework-based nanomaterials for electrochemical energy storage and conversion.

Author

Zheng, Yong, Khan, Niaz Ali, Ni, Xuepeng, Zhang, Kai A. I., Shen, Yi, Huang, Niu, Kong, Xin Ying, and Ye, Liqun

Subjects
ENERGY conversion, ENERGY storage, LITHIUM sulfur batteries, CARBON dioxide reduction, HYDROGEN evolution reactions, NANOSTRUCTURED materials
Abstract

Recently, the increasing concerns regarding environmental and energy-related issues due to the use of fossil fuels have triggered extensive research on sustainable electrochemical energy storage and conversion (EESC). In this case, covalent triazine frameworks (CTFs) possess a large surface area, tailorable conjugated structures, electron donating–accepting/conducting moieties, and excellent chemical and thermal stabilities. These merits make them leading candidates for EESC. However, their poor electrical conductivity impedes electron and ion conduction, leading to unsatisfactory electrochemical performances, which limit their commercial applications. Thus, to overcome these challenges, CTF-based nanocomposites and their derivatives such as heteroatom-doped porous carbons, which inherit most of the merits of pristine CTFs, lead to excellent performances in the field of EESC. In this review, initially, we briefly highlight the existing strategies for the synthesis of CTFs with application-targeted properties. Next, we review the contemporary progress of CTFs and their derivatives related to electrochemical energy storage (supercapacitors, alkali-ion batteries, lithium–sulfur batteries, etc.) and conversion (oxygen reduction/evolution reaction, hydrogen evolution reaction, carbon dioxide reduction reaction, etc.). Finally, we discuss perspectives on current challenges and recommendations for the further development of CTF-based nanomaterials in burgeoning EESC research. [ABSTRACT FROM AUTHOR]

Published
2023
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18. Mit sichtbarem Licht geförderte schaltbare selektive Oxidationen von Styrol über kovalente Triazin‐Gerüste in Wasser.

Author

Ayed, Cyrine, Yin, Jie, Landfester, Katharina, and Zhang, Kai. A. I.

Subjects
STYRENE, OXIDATION
Abstract

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2023
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21. A Nanographene‐Based Two‐Dimensional Covalent Organic Framework as a Stable and Efficient Photocatalyst

Author

Jin, Enquan, primary, Fu, Shuai, additional, Hanayama, Hiroki, additional, Addicoat, Matthew A., additional, Wei, Wenxin, additional, Chen, Qiang, additional, Graf, Robert, additional, Landfester, Katharina, additional, Bonn, Mischa, additional, Zhang, Kai A. I., additional, Wang, Hai I., additional, Müllen, Klaus, additional, and Narita, Akimitsu, additional

Published
2021
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22. A Nanographene‐Based Two‐Dimensional Covalent Organic Framework as a Stable and Efficient Photocatalyst

Author

Müllen, Klaus, primary, Jin, Enquan, additional, Fu, Shuai, additional, Hanayama, Hiroki, additional, Addicoat, Matthew A., additional, Wei, Wenxin, additional, Chen, Qiang, additional, Graf, Robert, additional, Landfester, Katharina, additional, Bonn, Mischa, additional, Zhang, Kai A. I., additional, Wang, Hai I., additional, and Narita, Akimitsu, additional

Published
2021
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46. A Nanographene‐Based Two‐Dimensional Covalent Organic Framework as a Stable and Efficient Photocatalyst.

Author

Jin, Enquan, Fu, Shuai, Hanayama, Hiroki, Addicoat, Matthew A., Wei, Wenxin, Chen, Qiang, Graf, Robert, Landfester, Katharina, Bonn, Mischa, Zhang, Kai A. I., Wang, Hai I., Müllen, Klaus, and Narita, Akimitsu

Subjects
POROUS polymers, CRYSTALLINE polymers, LIGHT absorption, X-ray powder diffraction, TRANSMISSION electron microscopy, CONJUGATED polymers
Abstract

Synthesis of covalent organic frameworks (COFs) with desirable organic units furnishes advanced materials with unique functionalities. As an emerging class of two‐dimensional (2D) COFs, sp2‐carbon‐conjugated COFs provide a facile platform to build highly stable and crystalline porous polymers. Herein, a 2D olefin‐linked COF was prepared by employing nanographene, namely, dibenzo[hi,st]ovalene (DBOV), as a building block. The DBOV‐COF exhibits unique ABC‐stacked lattices, enhanced stability, and charge‐carrier mobility of ≈0.6 cm2 V−1 s−1 inferred from ultrafast terahertz photoconductivity measurements. The ABC‐stacking structure was revealed by the high‐resolution transmission electron microscopy and powder X‐ray diffraction. DBOV‐COF demonstrated remarkable photocatalytic activity in hydroxylation, which was attributed to the exposure of narrow‐energy‐gap DBOV cores in the COF pores, in conjunction with efficient charge transport following light absorption. [ABSTRACT FROM AUTHOR]

Published
2022
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47. Proline‐Functionalized Magnetic Nanoparticles as Highly Performing Asymmetric Catalysts.

Author

Álvarez‐Bermúdez, Olaia, Landfester, Katharina, Zhang, Kai A. I., and Muñoz‐Espí, Rafael

Subjects
*MAGNETIC nanoparticles, *MAGNETIC cores, *CATALYTIC activity, *NANOPARTICLES, *ORGANIC solvents, *NITROALDOL reactions
Abstract

Amino acids have a crucial role in the field of asymmetric organocatalysis for the production of chiral compounds with high added value and specific biological activity. In particular, proline offers high activity and stereoselectivity for catalyzing aldol reactions in organic solvents. However, proline‐based catalysts often lack water‐solubility, accessibility, catalytic performance, or recovery in aqueous media. This work reports the design of proline‐functionalized poly(methyl methacrylate) (PMMA) nanoparticles with a magnetic core that offer high availability of chiral units in water and high recyclability. A proline‐based copolymerizable surfactant is designed and integrated onto the surface of PMMA nanoparticles through a miniemulsion polymerization process without using additional surfactants. The miniemulsion technique allows the incorporation of magnetite to the system to create a magnetically separable catalyst. The chiral nanocatalyst presents a high diastereoselective catalytic activity for the intermolecular aldol reaction between p‐nitrobenzaldehyde and cyclohexanone in water. [ABSTRACT FROM AUTHOR]

Published
2024
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