Synthesis of crumpled nanosheets of polymeric carbon nitride from melamine cyanurate

Carboxymethylation of Cinnamyl Alcohol with Dimethyl Carbonate over Graphitic Carbon Nitrides

A set of graphitic carbon nitride samples was prepared using a straightforward experimental procedure without templates and any subsequent treatments. The materials were studied in-depth using a range of physical and chemical methods such as X-ray diffraction, FTIR spectroscopy, elemental analysis (CHN), nitrogen physisorption, SEM, XPS, TPD CO2. The resulting g-C3N4 was shown to be highly efficient in carboxymethylation of cinnamyl alcohol with dimethyl carbonate yielding up to ca. 82 % of the desired cinnamyl methyl carbonate. In the studied conditions, an increase in the surface N atomic content leads to an increase in selectivity towards the desired carbonate, while a higher surface O content was beneficial for side products. Metal-free graphitic carbon nitride was shown to be one of the most productive (ca. 2 mol/h kgcat) in the investigated reaction among studied heterogeneous catalysts.

Nitrogen-doped lignin-derived electrode materials for supercapacitors were prepared using the domain-limited effect

Supercapacitors, pivotal in mitigating the energy crisis stemming from dwindling fossil fuel reservoirs, necessitate meticulous consideration of electrode material preparation. While lignin-derived carbon materials sourced sustainably exhibit commendable potential as electrode materials, their intrinsic low capacitance limits widespread utilization. Herein, nitrogen atom doping of lignin (CNL) was accomplished employing a chemical modification technique employing cyanuric chloride as a dopant. The resultant nitrogen content measured at 2.85 %. Subsequent to CNL carbonation, the generated C3N4 was selectively confined to the internal surface of the CNLMS-800 through a domain-limited activation method, thereby rendering it suitable for deployment as a supercapacitor electrode material. CNLMS-800 manifests a substantial specific surface area of 1778.0 m2 g-1 and a concomitantly diminutive pore size of 2.6 nm. Noteworthy, the specific capacitance of CNLMS-800 attains 473.0 F g-1 at a current density of 0.5 A g-1 in a 6 M KOH electrolyte. The resultant energy density reaches 39.0 Wh kg-1 at a power density of 338.0 W kg-1. Crucially, even after 20,000 charge/discharge cycles at a current density of 10 A g-1, the capacitance retention attains an impressive 87.5 % in the KOH electrolyte. This innovative utilization of sustainable resources for electrode fabrication epitomizes a seminal advancement in the field of energy technology.

Carbon Vacancies Steer the Activity in Dual Ni Carbon Nitride Photocatalysis

The manipulation of carbon nitride (CN) structures is one main avenue to enhance the activity of CN-based photocatalysts. Increasing the efficiency of photocatalytic heterogeneous materials is a critical step toward the realistic implementation of sustainable schemes for organic synthesis. However, limited knowledge of the structure/activity relationship in relation to subtle structural variations prevents a fully rational design of new photocatalytic materials, limiting practical applications. Here, the CN structure is engineered by means of a microwave treatment, and the structure of the material is shaped around its suitable functionality for Ni dual photocatalysis, with a resulting boosting of the reaction efficiency toward many CX (X = N, S, O) couplings. The combination of advanced characterization techniques and first-principle simulations reveals that this enhanced reactivity is due to the formation of carbon vacancies that evolve into triazole and imine N species able to suitably bind Ni complexes and harness highly efficient dual catalysis. The cost-effective microwave treatment proposed here appears as a versatile and sustainable approach to the design of CN-based photocatalysts for a wide range of industrially relevant organic synthetic reactions.

F,O,S-Codoped Graphitic Carbon Nitride as an Efficient Photocatalyst for the Synthesis of Benzoxazoles and Benzimidazoles

Graphitic carbon nitride (g-C3N4) is a metal-free heterogeneous catalyst that has attracted attention because of its good chemical stability, cost-effectiveness, and environmental friendliness. In the work presented herein, F,O,S-codoped carbon nitride was synthesized by heating a mixture of melamine cyanurate and trifluoromethanesulfonic acid at 550 °C for 50 min. The obtained product was characterized by transmission electron microscopy, infrared spectroscopy, X-ray powder diffraction, CHNS elemental analysis, total combustion-ion chromatography, X-ray photoelectron spectroscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, and UV-Vis spectroscopy. Results point to an F,O,S-codoped g-C3N4. The material was applied as a photocatalyst for the formation of benzoxazoles and benzimidazoles by condensation–aromatization of 2-aminophenol or 1,2-phenylenediamine with suitable aldehydes (viz. benzaldehyde, 4-chlorobenzaldehyde, 2-naphthaldehyde, 2-hydroxybenzaldehyde, and 2-methoxybenzaldehyde), obtaining yields of up to 90% in 15 min under visible light irradiation, with good selectivity and reusability. Thus, the reported findings suggest that this F,O,S-codoped g-C3N4 may hold promise as a metal-free photocatalyst for the rapid synthesis of 2-arylbenzoxazoles and 2-arylbenzimidazoles.

Multifunctional Nanocarriers Based on Chitosan Oligomers and Graphitic Carbon Nitride Assembly

In this study, a graphitic carbon nitride and chitosan oligomers (g-C3N4−COS) nanocarrier assembly, which was obtained by cross-linking with methacrylic anhydride (MA), was synthesized and characterized. Its characterization was carried out using infrared spectroscopy, elemental and thermal analyses, and transmission electron microscopy. The new nanocarriers (NCs), with an average particle size of 85 nm in diameter and a 0.25 dispersity index, showed photocatalytic activity (associated with the g-C3N4 moiety), susceptibility to enzymatic degradation (due to the presence of the COS moiety), and high encapsulation and moderate-high release efficiencies (>95% and >74%, respectively). As a proof of concept, the visible-light-driven photocatalytic activity of the NCs was tested for rhodamine B degradation and the reduction of uranium(VI) to uranium(IV). Regarding the potential of the nanocarriers for the encapsulation and delivery of bioactive products for crop protection, NCs loaded with Rubia tinctorum extracts were investigated in vitro against three Vitis vinifera phytopathogens (viz. Neofusicoccum parvum, Diplodia seriata, and Xylophilus ampelinus), obtaining minimum inhibitory concentration values of 750, 250, and 187.5 µg·mL−1, respectively. Their antifungal activity was further tested in vivo as a pruning wound protection product in young ‘Tempranillo’ grapevine plants that were artificially infected with the two aforementioned species of the family Botryosphaeriaceae, finding a significant reduction of the necrosis lengths in the inner woody tissues. Therefore, g-C3N4-MA-COS NCs may be put forward as a multifunctional platform for environmental and agrochemical delivery applications.

Prolific intercalation of VO2 (D)/polypyrrole/g-C3N4 as an energy storing electrode with remarkable capacitance

VO2 (D)/polypyrrole/g-C3N4 composites are synthesized through in situ chemical oxidation polymerization, and used as an electrode material for excellent energy storage.

A graphitic carbon nitride–titania nanocomposite as a promising catalyst support for electro-oxidation of methanol

A graphitic carbon nitride–titania nanocomposite has been synthesized as a catalyst support for Pt which enhanced the electrocatalytic methanol oxidation reaction.

Effects of Protonation, Hydroxylamination, and Hydrazination of g-C₃N₄ on the Performance of Matrimid®/g-C₃N₄ Membranes

One of the challenges to continue improving polymeric membranes properties involves the development of novel chemically modified fillers, such as nitrogen-rich 2-D nanomaterials. Graphitic carbon nitride (g-C₃N₄) has attracted significant interest as a new class of these fillers. Protonation is known to afford it desirable functionalities to form unique architectures for various applications. In the work presented herein, doping of Matrimid^® with protonated g-C₃N₄ to yield Matrimid^®/g-C₃N₄ mixed matrix membranes was found to improve gas separation by enhancing the selectivity for CO₂/CH₄ by up to 36.9% at 0.5 wt % filler doping. With a view to further enhancing the contribution of g-C₃N₄ to the performance of the composite membrane, oxygen plasma and hydrazine monohydrate treatments were also assayed as alternatives to protonation. Hydroxylamination by oxygen plasma treatment increased the selectivity for CO₂/CH₄ by up to 52.2% (at 2 wt % doping) and that for O₂/N₂ by up to 26.3% (at 0.5 wt % doping). Hydrazination led to lower enhancements in CO₂/CH₄ separation, by up to 11.4%. This study suggests that chemically-modified g-C₃N₄ may hold promise as an additive for modifying the surface of Matrimid^® and other membranes.

Melamine-derived graphitic carbon nitride as a new effective metal-free catalyst for Knoevenagel condensation of benzaldehyde with ethylcyanoacetate

Melamine-derived C₃N₄ was tested in Knoevenagel condensation of benzaldehyde with ethylcyanoacetate.

Photocatalytic activities of coke carbon/g-C3N4 and Bi metal/Bi mixed oxides/g-C3N4 nanohybrids for the degradation of pollutants in wastewater

Different g-C₃N₄ composite systems (coke carbon/g-C₃N₄, Bi/Bi₂WO₆/g-C₃N₄ and Bi/Bi₂MoO₆/g-C₃N₄) have been assessed as photocatalysts for wastewater pollutants removal. The coke carbon/g-C₃N₄ hybrid, produced by thermal treatment at 550 °C of a composite made from melamine cyanurate and coke, only showed activity under UV-light irradiation. On the other hand, inorganic Bi spheres/Bi mixed oxides/g-C₃N₄ nanohybrids (Bi/Bi₂WO₆/g-C₃N₄ and Bi/Bi₂MoO₆/g-C₃N₄ composites), produced by thermal reduction of Bi₂WO₆ or Bi₂MoO₆ by g-C₃N₄, exhibited a remarkable red-shift, up to 620 nm, and allowed the visible-light driven degradation of the contaminant, albeit in combination with some adsorption.