Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

S-Heptazine oligomers: promising structural models for graphitic carbon nitride.

ABSTRACT: Graphitic carbon nitride (g-CN) has interesting catalytic properties but is difficult to study due to its structure and how it is produced. In this study, linear s-heptazine oligomers were synthesized to serve as well-defined molecular models for g-CN. Cyclic voltammetry, absorption and emission spectroscopies showed a clear shift of properties towards those of g-CN as the number of heptazine units increased. DFT calculations supported the characterizations, and helped refine the properties observed.

SUBMITTER: Zambon A

PROVIDER: S-EPMC5954616 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

<i>s</i>-Heptazine oligomers: promising structural models for graphitic carbon nitride.

Zambon A A Mouesca J-M JM Gheorghiu C C Bayle P A PA Pécaut J J Claeys-Bruno M M Gambarelli S S Dubois L L

Chemical science 20151028 2

Graphitic carbon nitride (g-CN) has interesting catalytic properties but is difficult to study due to its structure and how it is produced. In this study, linear <i>s</i>-heptazine oligomers were synthesized to serve as well-defined molecular models for g-CN. Cyclic voltammetry, absorption and emission spectroscopies showed a clear shift of properties towards those of g-CN as the number of heptazine units increased. DFT calculations supported the characterizations, and helped refine the properti ...[more]

PMID: 29896365

Similar Datasets

From Triazine to Heptazine: Origin of Graphitic Carbon Nitride as a Photocatalyst.

Project description:Graphitic carbon nitride (g-CN) has emerged as a promising metal-free photocatalyst, while the catalytic mechanism for the photoinduced redox processes is still under investigation. Interestingly, this heptazine-based polymer optically behaves as a "quasi-monomer". In this work, we explore upstream from melem (the heptazine monomer) to the triazine-based melamine and melam and present several lines of theoretical/experimental evidence where the catalytic activity of g-CN originates from the electronic structure evolution of the C-N heterocyclic cores. Periodic density functional theory calculations reveal the strikingly different electronic structures of melem from its triazine-based counterparts. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy also provide consistent results in the structural and chemical bonding variations of these three relevant compounds. Both melam and melem were found to show stable photocatalytic activities, while the photocatalytic activity of melem is about 5.4 times higher than that of melam during the degradation of dyes under UV-visible light irradiation. In contrast to melamine and melam, the frontier electronic orbitals of the heptazine unit in melem are uniformly distributed and well complementary to each other, which further determine the terminal amines as primary reduction sites. These appealing electronic features in both the heterocyclic skeleton and the terminated functional groups can be inherited by the polymeric but quasi-monomeric g-CN, leading to its pronounced photocatalytic activity.

| S-EPMC7271407 | biostudies-literature

Structural Insights into Poly(Heptazine Imides): A Light-Storing Carbon Nitride Material for Dark Photocatalysis.

Project description:Solving the structure of carbon nitrides has been a long-standing challenge due to the low crystallinity and complex structures observed within this class of earth-abundant photocatalysts. Herein, we report on two-dimensional layered potassium poly(heptazine imide) (K-PHI) and its proton-exchanged counterpart (H-PHI), obtained by ionothermal synthesis using a molecular precursor route. We present a comprehensive analysis of the in-plane and three-dimensional structure of PHI. Transmission electron microscopy and solid-state NMR spectroscopy, supported by quantum-chemical calculations, suggest a planar, imide-bridged heptazine backbone with trigonal symmetry in both K-PHI and H-PHI, whereas pair distribution function analyses and X-ray powder diffraction using recursive-like simulations of planar defects point to a structure-directing function of the pore content. While the out-of-plane structure of K-PHI exhibits a unidirectional layer offset, mediated by hydrated potassium ions, H-PHI is characterized by a high degree of stacking faults due to the weaker structure directing influence of pore water. Structure-property relationships in PHI reveal that a loss of in-plane coherence, materializing in smaller lateral platelet dimensions and increased terminal cyanamide groups, correlates with improved photocatalytic performance. Size-optimized H-PHI is highly active toward photocatalytic hydrogen evolution, with a rate of 3363 μmol/gh H2 placing it on par with the most active carbon nitrides. K- and H-PHI adopt a uniquely long-lived photoreduced polaronic state in which light-induced electrons are stored for more than 6 h in the dark and released upon addition of a Pt cocatalyst. This work highlights the importance of structure-property relationships in carbon nitrides for the rational design of highly active hydrogen evolution photocatalysts.

| S-EPMC6768190 | biostudies-literature

Graphitic Carbon Nitride for Photocatalytic Air Treatment.

Project description:Graphitic carbon nitride (g-C3N4) is a conjugated polymer, which recently drew a lot of attention as a metal-free and UV and visible light responsive photocatalyst in the field of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability and earth-abundant nature. In the present work, bulk g-C3N4 was synthesized by thermal decomposition of melamine. This material was further exfoliated by thermal treatment. S-doped samples were prepared from thiourea or further treatment of exfoliated g-C3N4 by mesylchloride. Synthesized materials were applied for photocatalytic removal of air pollutants (acetaldehyde and NOx) according to the ISO 22197 and ISO 22197-1 methodology. The efficiency of acetaldehyde removal under UV irradiation was negligible for all g-C3N4 samples. This can be explained by the fact that g-C3N4 under irradiation does not directly form hydroxyl radicals, which are the primary oxidation species in acetaldehyde oxidation. It was proved by electron paramagnetic resonance (EPR) spectroscopy that the dominant species formed on the irradiated surface of g-C3N4 was the superoxide radical. Its production was responsible for a very high NOx removal efficiency not only under UV irradiation (which was comparable with that of TiO2), but also under visible irradiation.

| S-EPMC7372426 | biostudies-literature

Modification of Graphitic Carbon Nitride with Hydrogen Peroxide.

Project description:Graphitic carbon nitride (GCN) was synthetized by heating melamine and then it was thermally exfoliated for 1-3 h in air. Both bulk and exfoliated GCN nanomaterials were treated in the 10-30% aqueous solutions of H2O2 for us to study their modification. The light absorption properties were observed by the reddish color and the red-shifts of their UV-Vis spectra. The content of oxygen increased and hydrogen peroxide was supposed to partially oxidize C-OH groups to C=O ones and to form C-O-C groups instead of edge C-NH-C ones. The GCN structure changes were not observed. However, a surface modification of the GCN materials was recognized by their changed photocatalytic activities tested by means of Acid Orange 7 (AO7) and Rhodamines B (RhB), zeta-potentials, and neutralization titration curves.

| S-EPMC7559342 | biostudies-literature

Quenching-Induced Structural Distortion of Graphitic Carbon Nitride Nanostructures: Enhanced Photocatalytic Activity and Electrochemical Hydrogen Production.

Project description:Engineered nanomaterials are emerging in the field of environmental chemistry. This study involves the analysis of the structural, electronic, crystallinity, and morphological changes in graphitic carbon nitride (g-C3N4), an engineered nanomaterial, under rapid cooling conditions. X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller, Fourier transform infrared, Raman, band gap, and Mott-Schottky analyses strongly proved that the liquid N2-quenched sample of g-C3N4 has structural distortion. The photocatalytic efficiency of engineered g-C3N4 nanostructures was analyzed through the degradation of reactive red 120 (RR120), methylene blue (MB), rhodamine B, and bromophenol as a representative dye. The photocatalytic dye degradation efficiency was analyzed by UV-vis spectroscopy and total organic carbon (TOC) analysis. The photocatalytic efficiency of g-C3N4 under different quenching conditions included quenching at room temperature in ice and liquid N2. The degradation efficiencies are found to be 4.2, 14.7, and 82.33% for room-temperature, ice, and liquid N2 conditions, respectively. The pseudo-first-order reaction rate of N2-quenched g-C3N4 is 9 times greater than the ice-quenched g-C3N4. Further, the TOC analysis showed that 55% (MB) and 59% (RR120) of photocatalytic mineralization were achieved within a time duration of 120 min by the liquid N2-quenched g-C3N4 nanostructure. In addition, the quenched g-C3N4 electrocatalytic behavior was examined via the hydrogen (H2) evolution reaction in acidic medium. The liquid N2-quenched g-C3N4 catalyst showed a lower overpotential with high H2 evolution when compared with the other two g-C3N4-quenched samples. The results obtained provide an insight and extend the scope for the application of engineered g-C3N4 nanostructures in the degradation of organic pollutants as well as for H2 evolution.

| S-EPMC6648192 | biostudies-literature

Nitrogen-doped Carbon Nanospheres-Modified Graphitic Carbon Nitride with Outstanding Photocatalytic Activity.

Project description:Metals and metal oxides are widely used as photo/electro-catalysts for environmental remediation. However, there are many issues related to these metal-based catalysts for practical applications, such as high cost and detrimental environmental impact due to metal leaching. Carbon-based catalysts have the potential to overcome these limitations. In this study, monodisperse nitrogen-doped carbon nanospheres (NCs) were synthesized and loaded onto graphitic carbon nitride (g-C3N4, GCN) via a facile hydrothermal method for photocatalytic removal of sulfachloropyridazine (SCP). The prepared metal-free GCN-NC exhibited remarkably enhanced efficiency in SCP degradation. The nitrogen content in NC critically influences the physicochemical properties and performances of the resultant hybrids. The optimum nitrogen doping concentration was identified at 6.0 wt%. The SCP removal rates can be improved by a factor of 4.7 and 3.2, under UV and visible lights, by the GCN-NC composite due to the enhanced charge mobility and visible light harvesting. The mechanism of the improved photocatalytic performance and band structure alternation were further investigated by density functional theory (DFT) calculations. The DFT results confirm the high capability of the GCN-NC hybrids to activate the electron-hole pairs by reducing the band gap energy and efficiently separating electron/hole pairs. Superoxide and hydroxyl radicals are subsequently produced, leading to the efficient SCP removal.

| S-EPMC7770884 | biostudies-literature

Biopolymer-activated graphitic carbon nitride towards a sustainable photocathode material.

Project description:Photoelectrochemical (PEC) conversion of solar light into chemical fuels is one of the most promising solutions to the challenge of sustainable energy. Graphitic carbon (IV) nitride polymer (g-CN) is an interesting sustainable photocathode material due to low-cost, visible-light sensitivity, and chemical stability up to 500 °C in air. However, grain boundary effects and limited active sites greatly hamper g-CN activity. Here, we demonstrate biopolymer-activation of g-CN through simultaneous soft-templating of a sponge-like structure and incorporation of active carbon-dopant sites. This facile approach results in an almost 300% increase in the cathodic PEC activity of g-CN under simulated solar-irradiation.

| S-EPMC3703604 | biostudies-literature

The role of guanidine hydrochloride in graphitic carbon nitride synthesis.

Project description:Graphitic carbon nitride (CN) was synthesized from guanidine hydrochloride (G), melamine (M) and dicyandiamide (DCDA). The CN materials synthetized from the pure precursors and their mixtures were characterized by common methods, including thermal analysis, and their photocatalytic activities were tested by the degradation of selected organic pollutants, such as amoxicillin, phenol, Rhodamine B (RhB). Remarkable changes in their texture properties in terms of particle sizes, specific surface areas (SSA) and consequently their photocatalytic activity were explained by the role of guanidine hydrochloride in their synthesis. The SSA increased due to the release of NH3 and HCl and its complex reactions with melamine and DCDA forming structure imperfections and disruptions. The photocatalytic activity of the CN materials was found to be dependent on their SSA.

| S-EPMC8566454 | biostudies-literature

Graphitic carbon nitride nanosheet electrode-based high-performance ionic actuator.

Project description:Ionic actuators have attracted attention due to their remarkably large strain under low-voltage stimulation. Because actuation performance is mainly dominated by the electrochemical and electromechanical processes of the electrode layer, the electrode material and structure are crucial. Here, we report a graphitic carbon nitride nanosheet electrode-based ionic actuator that displays high electrochemical activity and electromechanical conversion abilities, including large specific capacitance (259.4 F g(-1)) with ionic liquid as the electrolyte, fast actuation response (0.5±0.03% in 300 ms), large electromechanical strain (0.93±0.03%) and high actuation stability (100,000 cycles) under 3 V. The key to the high performance lies in the hierarchical pore structure with dominant size <2 nm, optimal pyridinic nitrogen active sites (6.78%) and effective conductivity (382 S m(-1)) of the electrode. Our study represents an important step towards artificial muscle technology in which heteroatom modulation in electrodes plays an important role in promoting electrochemical actuation performance.

| S-EPMC4458862 | biostudies-literature

Room temperature synthesis of biodiesel using sulfonated graphitic carbon nitride.

Project description:Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, Sg-CN, which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature.

| S-EPMC5172360 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data