- Photocatalytic Hydrogen Evolution under Ambient Conditions on Polymeric Carbon Nitride/Donor-π-Acceptor Organic Molecule Heterostructures
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Efficient solar-to-hydrogen (STH) energy conversion under ambient conditions (room temperature and atmospheric pressure) is important for pursuing scalable solar hydrogen generation. Modification of polymeric carbon nitride (PCN) by conjugated polymers has attracted great attention for improving photocatalytic hydrogen evolution (PHE) performance. However, the limited interfacial junction between PCN and conjugated polymers leads to a low density of free charges, resulting in unsatisfactory PHE activity. Herein, three donor-π-acceptor-structured organic molecules (OMs) with different electron-donating units (amino, N,N-diethyl and triphenylamine) and same electron-accepting unit (benzothiadiazole) are designed to modify PCN to enlarge the interfacial junction. The optimized PHE performance under AM 1.5G simulated sunlight and ambient conditions can maintain as high as 4.63 mmol h?1 g?1 (the highest record among all the reported PCN-based photocatalysts to the best of the authors knowledge). The improved performance can be partially attributed to the strong visible light harvesting capability of OMs. Specifically, the triphenylamine unit in the formed type II molecule heterojunctions (MHJ) enables efficient charge separation at the interfacial junction, which prolongs the photogenerated electron lifetime for PHE. The designed MHJ photocatalysts show outstanding PHE performance under ambient conditions, which is highly promising for scalable STH conversion.
- Li, Kui,Wang, Lei,Chen, Zhongxin,Yang, Xianfeng,Yu, Yu-Xiang,Zhang, Wei-De,Wang, Ye,Shi, Yumeng,Loh, Kian Ping,Xu, Qing-Hua
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- Modulating Benzothiadiazole-Based Covalent Organic Frameworks via Halogenation for Enhanced Photocatalytic Water Splitting
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Two-dimensional covalent organic frameworks (2D COFs), an emerging class of crystalline porous polymers, have been recognized as a new platform for efficient solar-to-hydrogen energy conversion owing to their pre-designable structures and tailor-made functions. Herein, we demonstrate that slight modulation of the chemical structure of a typical photoactive 2D COF (Py-HTP-BT-COF) via chlorination (Py-ClTP-BT-COF) and fluorination (Py-FTP-BT-COF) can lead to dramatically enhanced photocatalytic H2 evolution rates (HER=177.50 μmol h?1 with a high apparent quantum efficiency (AQE) of 8.45 % for Py-ClTP-BT-COF). Halogen modulation at the photoactive benzothiadiazole moiety can efficiently suppress charge recombination and significantly reduce the energy barrier associated with the formation of H intermediate species (H*) on polymer surface. Our findings provide new prospects toward design and synthesis of highly active organic photocatalysts toward solar-to-chemical energy conversion.
- Chen, Long,Chen, Weiben,He, Feng,Mo, Daize,Wang, Lei,Wen, Zhilin,Wu, Xiaojun,Xu, Hangxun
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- Creating Graphitic Carbon Nitride Based Donor-π–Acceptor-π–Donor Structured Catalysts for Highly Photocatalytic Hydrogen Evolution
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Conjugated polymers with tailored donor–acceptor units have recently attracted considerable attention in organic photovoltaic devices due to the controlled optical bandgap and retained favorable separation of charge carriers. Inspired by these advantages, an effective strategy is presented to solve the main obstructions of graphitic carbon nitride (g-C3N4) photocatalyst for solar energy conversion, that is, inefficient visible light response and insufficient separation of photogenerated electrons and holes. Donor-π–acceptor-π–donor polymers are prepared by incorporating 4,4′-(benzoc 1,2,5 thiadiazole-4,7-diyl) dianiline (BD) into the g-C3N4 framework (UCN-BD). Benefiting from the visible light band tail caused by the extended π conjugation, UCN-BD possesses expanded visible light absorption range. More importantly, the BD monomer also acts as an electron acceptor, which endows UCN-BD with a high degree of intramolecular charge transfer. With this unique molecular structure, the optimized UCN-BD sample exhibits a superior performance for photocatalytic hydrogen evolution upon visible light illumination (3428 μmol h?1 g?1), which is nearly six times of that of the pristine g-C3N4. In addition, the photocatalytic property remains stable for six cycles in 3 d. This work provides an insight into the synthesis of g-C3N4-based D-π–A-π–D systems with highly visible light response and long lifetime of intramolecular charge carriers for solar fuel production.
- Li, Kui,Zhang, Wei-De
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- COVALENT ORGANIC FRAMEWORKS AND APPLICATIONS AS PHOTOCATALYSTS
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Described herein are covalent organic frameworks. The covalent organic frameworks have unique structural and physical properties, which lends them to be versatile in a number of different applications and uses. In one aspect, the covalent organic frameworks are composed of a plurality of fused aromatic groups and electron-deficient chromophores. The covalent organic frameworks are useful as photocatalysts in a number of different applications.
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- High-performing D-π-A-π-D benzothiadiazole-based hybrid local and charge-transfer emitters in solution-processed OLEDs
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Transforming triplet excitons into singlet excitons is a topic of great interest to material scientists in order to surpass the exciton utilization efficiency (EUE) limit of 25% in electro-fluorescent devices. Towards this goal, the donor-acceptor strategy of molecular design has been proven to be an effective approach to obtain high electroluminescence (EL) efficiency. In this context, herein, we report two benzothiadiazole (BTD)-based donor-acceptor π-conjugated fluorescent molecules, 1 and 2, which exhibited an external quantum efficiency (EQE) as high as 7.0% and 8.1%, respectively, in solution-processed doped green OLED devices. The observed high photoluminescence (PL) quantum yield of 81% for 1 and 85% for 2 corroborate the high EUE values of 43% and 48%, respectively, exceeding the traditional limit (25%), hence suggest the utilization of triplet excitons. The reported emitters combine two parameters, i.e. high PL efficiency and high EUE, which are of key importance to harvest maximum EL in OLED devices. Based on the photophysical (solvatochromic experiment) and quantum chemical calculations, the impacts of the D-π-A-π-D molecular design on the regulation of the locally excited and charge transfer components were revealed, which explained the observed high EQE (>5%) and EUE (>25%) values for the BTD-based emitters. The development of emitters with a hybrid local and charge transfer state in combination with the 'hot exciton' mechanism is an important strategy to produce highly efficient fluorescent-emitter materials. Besides the impressive EL properties of the emitters, the studied compound 1 as a chemosensor showed the selective sensing of metal cation (Fe2+) and anion (I-) together with the staining agent of Hibiscus rosa-sinensis pollen grains.
- Bala, Indu,Cheng, Chien-Hong,De, Joydip,Devi, Manisha,Jayakumar, Jayachandran,Jou, Jwo-Huei,Kailasam, Kamalakannan,Pal, Santanu Kumar,Singh, Nitya,Yadav, Rohit Ashok Kumar
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supporting information
p. 17009 - 17015
(2020/12/30)
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- Identification of Prime Factors to Maximize the Photocatalytic Hydrogen Evolution of Covalent Organic Frameworks
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Visible-light-driven hydrogen (H2) production from water is a promising strategy to convert and store solar energy as chemical energy. Covalent organic frameworks (COFs) are front runners among different classes of organic photocatalysts. The photocatalytic activity of COFs depends on numerous factors such as the electronic band gap, crystallinity, surface area, exciton migration, stability of transient species, charge separation and transport, etc. However, it is challenging to fine tune all of these factors simultaneously to enhance the photocatalytic activity. Hence, in this report, an effort has been made to understand the interplay of these factors and identify the key factors for efficient photocatalytic H2 production through a structure-property-activity relationship. Careful molecular engineering allowed us to optimize all of the above plausible factors impacting the overall catalytic activities of a series of isoreticular COFs. The present study determines three prime factors: light absorption, charge carrier generation, and its transport, which influence the photocatalytic H2 production of COFs to a much greater extent than the other factors.
- Abe, Ryu,Baburin, Igor,Ghosh, Samrat,Heine, Thomas,Kaji, Hironori,Kawaguchi, Takahiro,Kuc, Agnieszka,Nakada, Akinobu,Seki, Shu,Springer, Maximilian A.,Suzuki, Hajime,Suzuki, Katsuaki
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supporting information
p. 9752 - 9762
(2020/07/25)
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- Effect of the linkages on the self-assembly and photophysical properties of 4,7-diphenyl-2,1,3-benzothiadiazole-based luminescent polycatenars
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Three series of 4,7-diphenyl-2,1,3-benzothiadiazole (DBTD)based polycatenars containing a central 4,7-diphenyl-2,1,3-benzothiadiazole moiety connected to 3,4,5-trialkoxyl benzene units at both ends through ether (-OCH2-), ester (-OOC-)or amide (-HNCO-)linkages were synthesized via Suzuki coupling reaction as key step. The polarities of the linkages had great effect on their self-assembly and photophycial properties. Both ether and amide compounds were mesogens, while the ester compounds were non-mesogens. The ether compounds displayed Colhex/p6mm phases, while the amide compound displayed two kinds of columnar phases i.e. columnar rectangular phase with p2mm and columnar hexagonal phase with p6mm lattices depending on temperature. The column phases could be aligned in electric field or under mechanical shearing. The ether and amide compounds showed the significant red-shifted maximum absorption and emission. In the solid and gel states, both ether and amide compounds were yellow luminescence, while ester compounds were green luminescence.
- Hu, Jinliang,Xiao, Yulong,Chang, Qing,Gao, Hongfei,Cheng, Xiaohong
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- Fluorescent two-photon absorption benzothiadiazole dyes having photoreleasing quenchers
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Fluorescent two-photon absorption benzothiadiazole dye 5 provides significant fluorescence quenching by introducing nitrobenzene quencher moieties. The florescence intensity is recovered by photoreleasing of the quencher moieties upon irradiation. Copyrig
- Ishi-I, Tsutomu,Nakamura, Nami,Mine, Tomonori,Imamura, Satoru,Shigeiwa, Motoyuki,Gorohmaru, Hideki,Maeda, Shuuichi
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scheme or table
p. 1042 - 1043
(2010/06/17)
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