Oxide Carbon Nitride Research Articles

Copper decorated cuprous oxide–carbon nitride plasmonic p-n heterojunction with high-efficiently charge transfer for photodegradation of tetracycline

In this work, a novel copper decorated cuprous oxide–carbon nitride (Cu@Cu2O-g-C3N4) plasmonic p-n heterojunction was prepared by solvothermal method using pre-synthesized carbon nitride and Cu@Cu2O precursors as raw materials. The morphology observation for the sample exhibits that Cu2O precursor is dispersed from micrometer octahedrons to the particles with the sizes of 20 ∼ 200 nm under action of dimethylformamide, forming a close contact between Cu nanoparticles, Cu2O particles and g-C3N4 stacking flakes. The results of photodegradation shown that 96.4 % of 10 mg·L−1 tetracycline (TC) solution was decomposed within 60 min and degradation rate decreased by 9.2 % after five cycles. Photoelectrochemical characterizations indicated that photocatalytic performance of Cu@Cu2O-g-C3N4 was attributed to high-efficiently charge transfer base on the synergistic effect of heterojunction and plasmon resonance. The formation of p-n type built-in electric field between Cu@Cu2O and g-C3N4 enhances photocatalytic oxidative and reductive ability of the catalyst, and dual coupling effects induced by the localized surface plasmon resonance of Cu nanoparticles promote the amount of photogenerated electrons. This work provides a strategy for preparing efficient p-n heterojunction photocatalysts with plasma coupling effects by reconstructing the junction interface using facile solvothermal method.

The surface asymmetric site regulation of carbon nitride oxide enabling peroxymonosulfate activation for degrading tetracycline

Peroxymonosulfate (PMS) activation by the carbonaceous-based materials for degrading antibiotics is a recent emerging hotspot in water environment restoration. Herein, a triazine carbon material is prepared by urea thermal condensation follwed by water-mediated oxidation. The optimized triazine carbon material (CNOR15) can degrade around 100 % of tetracycline within 6 mins, thus pseudo-first-order kinetic constant (kobs) enhances approximately 49 folds compared to pristine carbon material. Experiments and characterizations demonstrate non-radical reactive species of 1O2 plays a crucial role in CNOR15/PMS system to eliminate tetracycline, in which performs at an asymmetric C = O site on the edge of triazine motief. Electron paramagnetic resonance and trapping tests comfirm the novel mechanism of electron conduction from sp/sp2-hybrdized triazine to C = O prompting PMS decomposition for 1O2 generation. Ex-situ argon sputtering XPS technology solidly unveils a underlysing linear corelation between catalysis activity and content of carbonyl-constructed assymetric sites. In addition, membranoid CNOR15/PVDF removes ca. 90 % tetracycline at a rate of 100 mL·min−1 in a continuous flow-cell device, exhibiting a promising application in the practical wastewater purification. Our work emphasized a significance of asymmetric site regulation of carbonaceous materials towards PMS activation for environmental remediation.

Effectively improve the mechanical properties of carbon fabric/epoxy composites by oxidized carbon nitride

AbstractIn this work, carbon nitride (C3N4) powder was oxidized by the Hummers oxidation method, and oxidized carbon nitride (O‐C3N4) was obtained. Epoxy (EP) was modified with O‐C3N4, and then carbon fiber fabric/epoxy (CF/EP) composites were prepared by hand‐pasting molding. The O‐C3N4 greatly improves the wettability of EP resin, enhances the interface properties of CF/EP composites, and makes the composites have better mechanical properties. The interlaminar shear strength (ILSS) is increased from 51.75 to 59.68 MPa, the tensile strength is increased from 564.54 to 635.39 MPa, the bending strength is increased from 809.64 to 938.81 MPa, and the impact strength is increased from 73.48 to 84.84 kJ/m2. Meanwhile, the dynamic mechanical properties of composites are also significantly improved. The energy storage modulus is increased from 14.9 to 21.4 GPa, with an increase of 43.6%.Highlights Developing carbon fiber composites is conducive to industrial applications. O‐C3N4 effectively improves the mechanical properties of the composite. O‐C3N4 has the advantages of simple synthesis, low costs, and light color. O‐C3N4 is rich in oxygen‐containing functional groups.

Tailoring the three-phase microenvironment surface to induce carbon nitride oxide generating ·O2– with 100% selectivity for ultrafast photodegradation tetracycline under visible light

The reactive oxygen species (ROS) contribute to photodegrading tetracycline (TC), which determines the overall efficiency of photocatalysts. Superoxide radical (·O2–) is one of the excellent ROS for photodegrading TC by carbon nitride. However, achieving hierarchical carbon nitride with efficient, stabile, and selective production of ·O2– via O2 photoreduction is a great challenge. Herein, a carbon nitride oxide nest (CNON6) with carbon/nitrogen vacancies (C-v, N-v) and oxygen substitution (O-s) was prepared via tailoring surface microenvironment. The CNON6 can photodegrade 82% of TC within 2 min under visible light, and the pseudo-first-order kinetic constant is 1.22 min−1, 24-fold higher than that of CN. The superior photoactivity is attributed to a unique surface microenvironment, which N-v increased photoelectric conversion efficiency, C-v enhanced O2 adsorption and O-s induced ·O2– evolution with ∼ 100% selectivity. Moreover, PVDF membrane-supported CNON6 (11.33 cm2, 0.88 mg/cm2) can completely remove TC from wastewater at a rate of 2.62 mg/h in a simulated industrial continuous flow cell. The cost-effectiveness assessment was $6.36/kg/h, implying the CNON6/PVDF has a bright application prospect in wastewater treatment. This work developed a surface microenvironment tailor strategy to design photocatalysts for efficient degradation of TC.

Metal-free oxidized carbon nitride for efficient sunlight-driven photocleavage of lignin β-O-4 bond

Benefitting from mild reaction conditions and good reusability, photocatalysis has industrial potential for high-value utilization of lignin waste. Commonly used metal sulfide photocatalysts present the risk of contamination of aromatic products by heavy metal ions due to photocorrosion. Here, a metal-free oxidized g-C3N4 photocatalyst was developed to selectively cleave the β-O-4 bond of lignin. Simple high-temperature oxidation treatment reduced carbon nitride size and scavenged the terminal NH2 groups, resulting in higher oxygen adsorption capacity and valence band potential. In the photoelectric effect, oxidized g-C3N4 exhibited lower carrier migration resistance and a longer photogenerated electron lifetime. The high oxygen adsorption and specific surface area led to a 160 % increase in superoxide radicals. Two routes for the photocatalytic cleavage β-O-4 bond in g-C3N4 are proposed. The catalytic activity of oxidized g-C3N4 is 8.5 times higher than that of untreated g-C3N4, the selective photocleavage reactivity attributed mainly to more OOH radicals and higher valence band potential. This work will provide a green and efficient strategy for the high-value conversion of lignin.

Minimizing base stoichiometry in Pd(0)/g-C3N4O catalyzed Suzuki–Miyaura cross-coupling reaction

A Pd nanoparticle supporting graphitic carbon nitride oxide (g-C3N4O) sheet is developed as an efficient heterogeneous catalyst for Suzuki–Miyaura cross-coupling reaction requiring just under a substoichiometric amount of exogenous base.

Strontium-Incorporated Carbon Nitride Nanosheets Modulate Intracellular Tension for Reinforced Bone Regeneration.

Strontium-containing agents have been demonstrated to elicit both bone anabolic and antiosteoporotic effects, showing great potential for the treatment of bone loss. However, an increased incidence of strontium-induced side effects restricts their clinical applications. Herein, oxidized carbon nitride nanosheets (CN) are delicately used to incorporate Sr2+ for the first time to achieve high osteogenic efficacy. The lamellar structure and enriched nitrogen species of CN provide them with a high surface area-to-volume ratio and abundant anchoring sites for Sr2+ incorporation. Importantly, Sr2+-incorporated CN (CNS) could synergistically promote osteoblast differentiation and bone regeneration at a single, very low Sr2+ dose. Mechanically, CNS could activate the FAK/RhoA signaling pathway to modulate the intracellular tension that stimulates osteoblasts differentiation. The present study will provide a new paradigm to enhance the efficacy of osteogenic metal ions by using lamellar nanocarriers.

Epoxy resin composites reinforced with sheet stripping oxidized carbon nitride

Epoxy resin composites reinforced with sheet stripping oxidized carbon nitride

Biomimetic Synthesis of PANI/Graphitic Oxidized Carbon Nitride for Supercapacitor Applications.

Polyaniline (PANI) composites have gained momentum as supercapacitive materials due to their high energy density and power density. However, some drawbacks in their performance remain, such as the low stability after hundreds of charge-discharge cycles and limitations in the synthesis scalability. Herein, we report for the first time PANI-Graphitic oxidized carbon nitride composites as potential supercapacitor material. The biomimetic polymerization of aniline assisted by hematin, supported by phosphorous and oxygen-modified carbon nitrides (g-POCN and g-OCN, respectively), achieved up to 89% yield. The obtained PAI/g-POCN and PANI/g-OCN show enhanced electrochemical properties, such as conductivity of up to 0.0375 S/cm, specific capacitances (Cs) of up to 294 F/g (at high current densities, 5 A/g) and a stable operation after 500 charge-discharge cycles (at 3 A/g). In contrast, the biomimetic synthesis of Free PANI, assisted by stabilized hematin in cosolvents, exhibited lower performance properties (65%). Due to their structural differences, the electrochemical properties of Free PANI (conductivity of 0.0045 S/cm and Cs of up to 82 F/g at 5 A/g) were lower than those of nanostructured PANI/g-POCN and g-OCN supports, which provide stability and improve the properties of biomimetically synthesized PANI. This work reveals the biomimetic synthesis of PANI, assisted by hematin supported by modified carbon nitrides, as a promising strategy to produce nanostructured supercapacitors with high performance.

An avenue to Chan-Lam N-arylation by Cu(0) nanoparticles immobilized graphitic carbon-nitride oxide surface

We report the immobilization of Cu(0) nanoparticles (NPs) with an average size of 7–8 nm on a template-free carbon-nitride oxide surface (g-C3N4O) in water medium. The heterogeneous surface containing Cu(0) NPs offers Lewis basic sites, which facilitate Chan-Lam N-arylation of anilines, azoles and indoles with phenylboronic acids. Good to moderate yields (55–93 %) of synthetically important N-arylanilines, N-aryl-1H-imidazoles, N-aryl-1H-benzimidazoles and N-aryl-1H-indoles are obtained, all of which have wide pharmaceutical applications. The reaction takes place under heterogeneous catalysis and the catalyst can be reused up to five catalytic cycles of the reaction. The stability of Cu(0) on the g-C3N4O surface, utilization of greener solvents for syntheses and extension of scope of Chan-Lam cross-coupling reaction through the introduction of Cu(0) catalysis are some of the significant achievements of this work.

In situ growing Cu2(OH)2CO3 on oxidized carbon nitride with enhanced photocatalytic hydrogen evolution and pollutant degradation

A novel composite has been successfully synthesized in situ via a coprecipitation method about the coupling of Cu2(OH)2CO3 with oxidized carbon nitride (O-g-C3N4) forming Cu2(OH)2CO3/O-g-C3N4 (CuCN) heterojunction structure. The as-prepared composites were characterized by diverse means. The CuCN composite with 3:5 mass ratio of Cu2(OH)2CO3 to O-g-C3N4 (60CuCN) presented an extremely excellent photocatalytic activity. The photocatalytic H2 evolution of 60CuCN was around 23.26 and 44.62 times higher than that of g-C3N4 and Cu2(OH)2CO3, respectively. The photocatalytic degradation malachite green (MG) rate of 60CuCN was up to 91%, which was around 2.2 and 4.8 times as much as that of g-C3N4 and Cu2(OH)2CO3, respectively. These results are mainly attributed to the structure property of O-g-C3N4 and the heterojunction structure of the composite, which could effectively accelerate the separation and transfer rate of photogenerated electrons and holes. The holes (h+) and superoxide radicals (·O2−) played a dominant role in photocatalytic degradation MG reaction.

Bifunctional iron-modified graphitic carbon nitride (g-C3N4) for simultaneous oxidation and adsorption of arsenic

Iron-modified graphitic carbon nitride (FG materials) was prepared through a simple and cost-effective method using iron oxide and melamine to achieve simultaneous oxidation and adsorption of arsenic. We hypothesized that graphitic carbon nitride oxidizes As(III) to As(V) under light irradiation, and the converted As(V) is adsorbed by the amorphous iron phase on FG materials. FG materials were characterized by X-ray diffraction, Fourier transform infrared spectra, field-emission scanning electron microscopy, specific surface area, ultraviolet–visible light spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy. As(III) was efficiently transformed to As(V) due to the photocatalytic-oxidation ability of graphic carbon nitride under visible and UV light irradiation, the oxidized As(V) was adsorbed by the amorphous iron phases, and As species were removed from the system. The removal efficiency of As(III) decreased from 50%, 41%, and 33% under UV light, visible light and dark, respectively. FG materials exhibited the photocatalytic-oxidation ability and adsorption capacity, and a synergistic effect was observed between graphitic carbon nitride and iron oxide. Removal of As can be achieved even under visible light, confirming the field applicability of low-cost FG materials.

In English

As an one of the most promising materials of green energy as a photocatalyst for the production of hydrogen from renewable, natural sources (water, greenhouse gas) and environmental remediation through the degradation of toxic organic pollutants, graphite-like carbon nitride (characterized as a non-toxic and chemically highly resistant material) and its nanostructured and doped (especially by oxygen atoms) derivatives attract special attention. The actual task for expanding the scope of application of g-C 3 N 4 is to improve and optimize its catalytic, electronic and optical properties by increasing both the surface area of graphitic carbon nitride and the number of active centers of the carbon nitride network due to doping of carbon nitride. The use of a mixture of two different precursors ensures the creation of heterojunctions, and as a result, an improvement the photocatalytic characteristics of g-C 3 N 4 . The oxygen-doped carbon nitride (O-g-C 3 N 4 ) and water-soluble carbon nitride oxide (g-C 3 N 4 )O was simultaneously synthesized by the gas phase method under special reaction conditions of pyrolysis of cyanuric acid and urea mixture. Reduction by the hydroquinone of carbon nitride oxide (g-C 3 N 4 )O yields nanostructured reduced carbon nitride (or reduced multilayer azagraphene). Obtained products were characterized by using Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), chemical and X-ray diffraction (XRD) analyses, scanning electron microscopy (SEM). According to the results of XPS and IR spectrometry the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride (RCN) correspond to the bonds in a synthesized carbon nitride (SCN). However, according to XRD results, reduced carbon nitride (RCN) probably consists of poorly connected heteroatomic azagraphene layers, because it has a significantly larger (on 0.09 nm) interplanar distance between the adjacent nitrogen-carbon layers than interplanar distance between the layers of synthesized carbon nitride (SCN). By SEM characterization it was found that the pyrolysis of a mixture of various precursors (cyanuric acid and urea) yielded a product with smaller crystalline domains (which can improve photocatalytic characteristics) than the pyrolysis of a single precursor (urea only).

Thin PEGylated Carbon Nitrides: Water-Dispersible Organic Nanodots as Bioimaging Probes.

Fluorescent materials are being used for the optical/fluorescence imaging of living cells and animal models. As such, the development of heavy-metal-free, water-dispersible, and biocompatible imaging probes is still important. Carbon nitride (C3 N4 ) is used as a bioimaging probe due to its suitable optical properties, thus enhancing its biocompatibility and dispersibility in aqueous media is required. In this study, we incorporated short-chain polyethylene glycol (PEG) groups onto a carbon nitride network by the simple N-alkylation of hexaethylene glycolic mesylate with nucleophilic nitrogen atoms on oxidized carbon nitride (OCN). The PEGylated OCN (PEG-OCN) was well dispersed in water as nanodots with a lateral dimension of approximately 30 nm and a thickness of 0.5-1.2 nm and showed strong photoluminescence in the visible region. Cell-viability testing confirmed that these "heavy-metal-free" organic nanodots were highly biocompatible and noncytotoxic. In particular, the developed nanodots could provide clear confocal images of RAW 264.7 cells without weakening cell activity and displaying any aggregation in a range of concentrations (25-100 μg mL-1 ) with bright-green emission in the cytoplasm.

Synthesis of High-Quality Crystalline Carbon Nitride Oxide by Selectively Driving the High-Temperature Instability of Urea with Pressure

One-step synthesis using only physical tools is an appealing “green” method for the realization of technological materials. High-pressure conditions are particularly suitable in the attainment of extended supramolecular networks and in combination with high-temperature are effective in selecting specific reaction pathways to increase product quality. Here we show how pressures below 3 GPa and temperatures on the order of 420 K are effective for the synthesis, from urea crystal phase IV, of 2D graphitic carbon nitride oxide with enhanced crystalline quality. Angle-dispersive X-ray diffraction and Fourier transform IR spectroscopy show that the reaction becomes less selective at higher pressure with the formation of melamine and ammonium carbamate as byproducts. An anomalous positive slope is shown by the P–T instability boundary, likely arising from unfavorable hydrogen bonding with respect to the topochemical path, making urea an interesting case study for gaining insight into the role of hydrogen bonding in solid-state reactivity.

Simultaneous photodegradation of multi-herbicides by oxidized carbon nitride: performance and practical application

This work focuses on photodegradation of multi-herbicides simultaneously with series oxidized carbon nitrides (OCN), which were synthesized via a rapid acid-assisted method. Carbon nitrides, after treating with nitric acid solution at several concentrations, revealed variant oxygen content, surface morphology and structure characteristic. The photocatalytic activity was verified by degradation of ten typical herbicides in water. The influence of microplastics on the photocatalytic performance of OCN sample was investigated for the first time. Experimental results showed that microplastics contained in environmental matrix significantly influenced the photodegradation ratio. Moreover, holes (h+) and OH radicals were found to be the main reactive species during this process. The OCN-10 sample demonstrated favourable reusability in recycling tests and exhibited satisfactory degradative capability for ten investigated herbicides both in soil and aqueous phase under simulated diurnal cycle.

Synthesis of reduced carbon nitride at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C3N4)O

For the first time at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C3N4)O reduced carbon nitride (or reduced multi-layer azagraphene) is obtained. It is differed from usually synthesized carbon nitride by a significantly large (on 0.09nm) interplanar distance is. At the same time, the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride correspond to the bonds in a synthesized g-C3N4. The samples of water-soluble carbon nitride oxide were synthesized under the special reactionary conditions of a pyrolysis of melamine and urea. We believe that reduced carbon nitride consists of weakly connected carbon-nitrogen monosheets (azagraphene sheets) as well as reduced (from graphene oxide) graphene contains weakly connected graphene sheets.

Features of the synthesis of carbon nitride oxide (g-C3N4)O at urea pyrolysis

First from urea was synthesized carbon nitride oxide (g-C3N4)O which is formed in a vapor gas reactionary space and is deposited outside of a place of precursor localization. The reaction of urea conversion was investigated in an interval of temperatures 350–450°С, but carbon nitride oxide is detected in the products of pyrolysis only at temperatures above 430°С. Carbon nitride oxide is dissolved in water and at a reducing it by hydroquinone is formed reduced carbon nitride oxide consisting, as we believe, from azagraphene sheets.

Production of Metal-Free Composites Composed of Graphite Oxide and Oxidized Carbon Nitride Nanodots and Their Enhanced Photocatalytic Performances.

A novel metal-free composite (GN) composed of two types of carbon-based nanomaterials, graphite oxide (GO) and 2D oxidized carbon nitride (OCN) nanodots was produced. Chemical and morphological characterizations reveal that GN contains a main component of GO with well-dispersed 2D OCN nanodots. GN shows enhanced photocatalytic performance for degrading an organic pollutant, Rhodamine B, under visible light.

Electron spin-polarization and spin-gapless states in an oxidized carbon nitride monolayer

A stable 2D spin-gapless honeycomb lattice oxidized carbon nitride material, C2NO.