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Carbon nitride1 (C3N4) was the Molecule of the Week for January 16 of this year. It exists in two major allotropes, β-C3N4, with a diamond-like structure and g-C3N4, whose properties resemble graphite. It turned out that g-C3N4 is the more valuable material, as a semiconductor and photocatalyst.
In recent years, various forms of oxidized graphitic carbon nitride (O-g-C3N4) have been found to have exceptional properties as well. An example of the structure of O-g-C3N4 is shown in the image; in this case, the substance contains hydrogen atoms along with carbon, nitrogen, and oxygen.
Examples of applications of O-g-C3N4 follow:
- Teresa J. Bandosz and co-workers at the City College of New York used a copper–benzene tricarboxylic acid metal–organic framework and O-g-C3N4 nanospheres to prepare a composite with a hierarchical pore structure. The composite was photocatalytically active and could adsorb and detoxify an organophosphate nerve agent surrogate (2016).
- Lorenzo Malavasi, Paolo Quadrelli, and colleagues at the University of Pavia (Italy) found that O-g-C3N4 is a good photocatalyst for generating singlet oxygen (1O2). They gave examples of using generated 1O2 in hetero-Diels–Alder reactions and ene reactions (2019).
- Juan I. Paredes, Alireza Z. Moshfegh, and coauthors at Sharif University of Technology (Tehran) and the Instituto Nacional del Carbón (Oviedo, Spain) used O-g-C3N4 nanosheets for water remediation. The nanosheets were effective adsorbents for removing organic dyes and the antibiotic tetracycline (2019).
- Venkata Krishnan and co-workers at the Indian Institute of Technology in Mandi and Ropar developed O-g-C3N4 as a sustainable metal-free catalyst for hydrogen transfer reactions under mild conditions (2020).
No hazard information for O-g-C3N4 has been reported, but it is expected that its safety profile would be similar to that of the unoxidized form.
1. CAS Reg. No. 143334-20-7.
MOTW updates
Quercetin1 was the Molecule of the Week for December 9, 2013. It is an abundant flavonoid in nature. For many years, it has been used to treat conditions ranging from eczema to cancer, with no scientific proof of its effectiveness. Quercetin is found in grapes and is now suspected of causing headaches associated with red wine.
In November, Apramita Devi, Morris Levin, and Andrew L. Waterhouse* at the University of California, Davis, reported that quercetin, which converts to the more bioavailable quercetin-3-glucuronide2 in vivo, inhibits a variant of the mitochondrial enzyme aldehyde dehydrogenase (ALDH2). Normal ALDH2 eliminates headache-causing acetaldehyde, a metabolite of ethanol; but the dysfunctional variant allows acetaldehyde to accumulate. The authors state that human-subject testing is needed to test their hypothesis.
Guaifenesin3 was the Molecule of the Week for November 21, 2005. It is an expectorant found in over-the-counter cough and cold medicines. It has been around since the 1940s; but in 2014, Agathe Hoffer-Schaefer and colleagues at Virginia Commonwealth University (Richmond) reported that a 378-subject study found no significant differences between guaifenesin and placebo.
Glyphosate4 was the Molecule of the Week for October 5, 2009. It has been a widely used broadleaf herbicide for more than 40 years. In the 2010s, it was suspected of causing non-Hodgkins lymphoma in farm workers; but in 2017, a long-term, 54,000 subject study found no connection between glyphosate use and cancer. Last month, the European Commission announced that glyphosate can remain on the market in the European Union for 10 years with new restrictions, including a ban on use of the chemical to dry crops before harvest and measures to protect nontarget species.
1. CAS Reg. No. 117-39-5.
2. CAS Reg. No. 22688-79-5.
3. CAS Reg. No. 93-14-1.
4. CAS Reg. No. 1071-83-6.
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Oxidized graphitic carbon nitride fast facts
| CAS Reg. No. | 344793-26-6 |
| SciFinder nomenclature | Carbon nitride oxide |
| Empirical formula | CxNxOx |
| Molar mass | Variable |
| Appearance | Off-white to yellowish-brown crystals or powdera |
| Melting point | 600–700 °C (dec.)a |
| Water solubility | Insoluble |
a. Data for unoxidized graphitic carbon nitride.
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