Synthesis of Triazine‐Based Materials by Functionalization with Alkynes

Braml, Nicole E.; Stegbauer, Linus; Lotsch, Bettina V.; Schnick, Wolfgang

doi:10.1002/chem.201405023

Cited by 9 publications

(1 citation statement)

References 44 publications

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“…This surprising finding suggests that the active chemical species responsible for the cooperative near-doubling of the hydrogen evolution rate in the blend is likely a low molecular weight oligomer or molecular unit rather than an extended higher-dimensional nanostructure. These results appear to be consistent with recent reports by Lotsch et al, 10,11,58,92 suggesting that oligomers and molecular heptazine-based materials may be promising future targets for next-generation organic photocatalysts.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Ultrafast Spectroscopy Reveals Electron-Transfer Cascade That Improves Hydrogen Evolution with Carbon Nitride Photocatalysts

2017

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Solar hydrogen generation from water represents a compelling component of a future sustainable energy portfolio. Recently, chemically robust heptazine-based polymers known as graphitic carbon nitrides (g-CN) have emerged as promising photocatalysts for hydrogen evolution using visible light while withstanding harsh chemical environments. However, since g-CN electron-transfer dynamics are poorly understood, rational design rules for improving activity remain unclear. Here, we use visible and near-infrared femtosecond transient absorption (TA) spectroscopy to reveal an electron-transfer cascade that correlates with a near-doubling in photocatalytic activity from 2050 to 3810 μmol h g when we infuse a suspension of bulk g-CN with 10% mass loading of chemically exfoliated carbon nitride. TA spectroscopy indicates that exfoliated carbon nitride quenches photogenerated electrons on g-CN at rates approaching the molecular diffusion limit. The TA signal for photogenerated electrons on g-CN decays with a time constant of 1/k' = 660 ps in the mixture versus 1/k = 4.1 ns in g-CN alone. Our TA measurements suggest that the charge generation efficiency in g-CN is greater than 65%. Exfoliated carbon nitride, which liberates only trace hydrogen levels when photoexcited directly, does not appear to independently sustain appreciable long-lived charge generation. Thus, the activity enhancement in the two-component infusion evidently results from a cooperative effect in which charge is generated on g-CN, followed by electron transfer to exfoliated carbon nitride containing photocatalytic chain terminations. This correlation between electron transfer and photocatalytic activity provides new insight into structural modifications for controlling charge separation dynamics and activity of carbon-based photocatalysts.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Ultrafast Spectroscopy Reveals Electron-Transfer Cascade That Improves Hydrogen Evolution with Carbon Nitride Photocatalysts

2017

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Twinned Growth of Metal‐Free, Triazine‐Based Photocatalyst Films as Mixed‐Dimensional (2D/3D) van der Waals Heterostructures

et al. 2017

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Design and synthesis of ordered, metal-free layered materials is intrinsically difficult due to the limitations of vapor deposition processes that are used in their making. Mixed-dimensional (2D/3D) metal-free van der Waals (vdW) heterostructures based on triazine (C N ) linkers grow as large area, transparent yellow-orange membranes on copper surfaces from solution. The membranes have an indirect band gap (E = 1.91 eV, E = 1.84 eV) and are moderately porous (124 m g ). The material consists of a crystalline 2D phase that is fully sp hybridized and provides structural stability, and an amorphous, porous phase with mixed sp -sp hybridization. Interestingly, this 2D/3D vdW heterostructure grows in a twinned mechanism from a one-pot reaction mixture: unprecedented for metal-free frameworks and a direct consequence of on-catalyst synthesis. Thanks to the efficient type I heterojunction, electron transfer processes are fundamentally improved and hence, the material is capable of metal-free, light-induced hydrogen evolution from water without the need for a noble metal cocatalyst (34 µmol h g without Pt). The results highlight that twinned growth mechanisms are observed in the realm of "wet" chemistry, and that they can be used to fabricate otherwise challenging 2D/3D vdW heterostructures with composite properties.

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Exploring triazine and heptazine based self assembled molecular materials through first principles investigations

2018

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Two-dimensional materials formed from the molecular self assembly of monomers through noncovalent interactions are of great importance in designing complex nanostructures with desired properties. The carbon nitride based heterocyclic systems, triazine and heptazine, are found to be promising candidates for generating various self assembled materials through (N....H) hydrogen bonding. Here, we explored graphyne and graphdiyne-like self assembled structures for carbon nitride materials using the density functional theory calculations. We systematically investigated the monolayer structures, stacked structures in different configurations, as well as the surface assembled structures on the Au(111) surface. In all four different monolayer structures, the monomers interact through the N...H hydrogen bonding. The electronic structure results indicate that the electronic properties in these structures can be tuned through the variation in the length of the acetylinic unit. The minimum energy stacked bilayer structure of triazine based material exactly matches with the experimentally reported structure. Surface assembled studies of the triazine based system show strong interaction between the Au(111) surface and the carbon nitride monolayer. Graphical abstract Self assembled two-dimensional molecular materials as well as the surface assemblies of triazine and heptazine based precursors are computationally investigated.

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Synthesis of Triazine‐Based Materials by Functionalization with Alkynes

Cited by 9 publications

References 44 publications

Ultrafast Spectroscopy Reveals Electron-Transfer Cascade That Improves Hydrogen Evolution with Carbon Nitride Photocatalysts

Ultrafast Spectroscopy Reveals Electron-Transfer Cascade That Improves Hydrogen Evolution with Carbon Nitride Photocatalysts

Twinned Growth of Metal‐Free, Triazine‐Based Photocatalyst Films as Mixed‐Dimensional (2D/3D) van der Waals Heterostructures

Exploring triazine and heptazine based self assembled molecular materials through first principles investigations

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