Browsing by Author "Hung, Ying-Hui"

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A Hollow Microtubular Triazine- and Benzobisoxazole-Based Covalent Organic Framework Presenting Sponge-Like Shells That Functions as a High-Performance Supercapacitor
(2019-05-02)
El-Mahdy, Ahmed F. M.
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Hung, Ying-Hui
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Mansoure, Tharwat Hassan
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Yu, Hsiao-Hua
;
Chen, Tao
In this paper we report the construction of a hollow microtubular triazine- and benzobisoxazole-based covalent organic framework (COF) presenting a sponge-like shell through a template-free [3+2] condensation of the planar molecules 2,4,6-tris(4-formylphenyl)triazine (TPT-3CHO) and 2,5-diaminohydroquinone dihydrochloride (DAHQ-2HCl). The synthesized COF exhibited extremely high crystallinity, a high surface area (ca. 1855m(2)g(-1)), and ultrahigh thermal stability. Interestingly, a time-dependent study of the formation of the hollow microtubular COF having a sponge-like shell revealed a transformation from initial ribbon-like crystallites into a hollow tubular structure, and confirmed that the hollow nature of the synthesized COF was controlled by inside-out Ostwald ripening, while the non-interaction of the crystallites on the outer surface was responsible for the sponge-like surface of the tubules. This COF exhibited significant supercapacitor performance: a high specific capacitance of 256Fg(-1) at a current density of 0.5Ag(-1), excellent cycling stability (98.8% capacitance retention over 1850cycles), and a high energy density of 43Whkg(-1). Such hollow structural COFs with sponge-like shells appear to have great potential for use as high-performance supercapacitors in energy storage applications.
Synthesis of [3+3] beta-ketoenamine-tethered covalent organic frameworks (COFs) for high-performance supercapacitance and CO2 storage
(2019-10-01)
El-Mandy, Ahmed F. M.
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Hung, Ying-Hui
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Mansoure, Tharwat Hassan
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Yu, Hsiao-Hua
;
Hsu, Yu-Shen
We report three new beta-ketoenamine-linked covalent organic frameworks (COFs) prepared through Schiff-base [3+3] polycondensations of 1,3,5-triformylphloroglucinol (TFP-3OHCHO) with three tris(aminophenyl)-presenting derivatives-featuring amino, carbazole, and pyridine units, respectively under solvothermal conditions. The resultant TFP-COFs possessed high BET specific surface area up to 686 m(2) g(-1) and excellent crystallinity, which showed excellent electrochemical specific capacitances (up to 291.1 F g(-1)) and CO2 uptake efficiency up to 200 mg g(-1) at 273 K. We propose the enhanced performance in supercapacitor and gas storage is owing to the conjugated enamine structures with redox-active triphenyl amino, carbazole, and pyridine moieties. In addition, we further investigate the formation mechanism of the spherical TFP-TPA COF by studying the morphological changes over time. The presence of more highly planar monomer units in the hexagonal structures of the resultant COFs led to stronger quadrupolar interaction with the included CO2 molecules. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.