Carbon Nitride Research Articles

Use of graphitic carbon nitrides as solar-light-driven photocatalysts for the reduction of p-nitrobenzoic acid

The use of graphitic carbon nitrides (g-C3N4) as photocatalysts for the reduction of p-nitrobenzoic acid (PNBA) under simulated sunlight has been investigated. The photocatalysts were synthesized through the thermal polymerization of melamine and urea. The effects of the g-C3N4 precursor employed in the synthesis, the thermal exfoliation treatment, the addition of sacrificial agents, and the pH conditions were evaluated. It was found that the presence of carboxylic acids as sacrificial electron donors was required to attain the photocatalytic reduction of PNBA, while amines or alcohols did not lead to any activity for this purpose. Furthermore, it was observed that the precursor used in the synthesis of graphitic carbon nitride had a slight influence on the photocatalytic activity, whereas the thermal treatment of the bulk g-C3N4 materials exhibited a favourable effect. The best results were obtained upon addition of oxalic acid at pH = 3 using the carbon nitride exfoliated materials, achieving in these conditions the complete removal of PNBA after ca. 60min of irradiation. Time resolved profiles of p-aminobenzoic acid (PABA) agree with an initial reduction of PNBA to form this compound, followed by oxidation of PABA by reactive oxygen species formed in the reaction medium.

Cyano and defective co-modified carbon nitride for optimized photoreformation of glucose to arabinose

Cyano and defective co-modified carbon nitride for optimized photoreformation of glucose to arabinose

Biaxila strain modulated high anisotropic gas-sensing performance of C5N-based two-dimensional devices: A first-principles study

Two-dimensional carbon nitride materials have been widely used in many applications such as device fabrication, gas adsorption and separation due to their abundant element resources, high physicochemical stability and excellent electronic properties. In this paper, density functional theory and non-equilibrium Green's function method are used to study the electronic structure, transport characteristics and gas sensitivity of C5N-based structures. The results show that the electron transport exhibits obvious anisotropy, in which the electron transport in the armchair direction is more conductive than that in the zigzag direction. It is worth noting that the negative differential resistance effect exists in both directions. Furthermore, the transport and sensing characteristics of inorganic molecules (NO, CO, NO2, SO2, and NH3) adsorbed on the C5N monolayer are studied. The results show that CO, SO2 and NH3 exist on the surface of C5N in the form of physical adsorption, while NO and NO2 adhere to the surface of C5N in the form of chemical adsorption. The designed C5N gas sensor exhibits high sensitivity to NO and NO2 molecules, reaching 81 % sensitivity to NO2 at a 0.1 V bias voltage. Finally, the effect of strain on the adsorption properties of gas sensing devices is studied. Studies have shown that the application of -4 % strain in the armchair direction significantly increases the current of NO and NO2, significantly improving the performance of the gas sensor. Whether strain is applied to the device or gas adsorption, C5N materials always maintain significant anisotropy. This study shows that C5N is a highly anisotropic and sensitive two-dimensional material, which has broad application potential in the field of electronic properties and gas sensing.

Selective Photocatalytic Dehydrogenation of Formic Acid on Graphite Carbon Nitride with Dual-Sited Cobalt and Platinum Cocatalysts

Selective Photocatalytic Dehydrogenation of Formic Acid on Graphite Carbon Nitride with Dual-Sited Cobalt and Platinum Cocatalysts

Investigation into the Exciton Binding Energy of Carbon Nitrides on Band Structure and Carrier Concentration through the Photoluminescence Effect

Carbon nitrides form a series of polymer semiconductors popular in photocatalysis. In the course of photoresponse, the separation of light-induced electron–hole pairs is one of the critical factors that affect the conversion rate from photoenergy to chemical substance. Exciton binding energy (Eb) is treated as a classical parameter to evaluate the barrier of exciton dissociation. In this work, we study the electronic and optical nature of two specific members of the carbon nitride family, polymeric carbon nitride (melon) and crystallized poly(triazine imide) (PTI/Li+Cl−) by employing the photoluminescence spectra and density functional theory (DFT) calculations based on the Wannier-Mott exciton module. The results of self-consistent GW computation were applied. The measurement of photoluminescence spectra, by which exciton binding energies are estimated, is likewise discussed. Generally, compared with the results calculated by GW-BSE, the DFT results based on the Wannier-Mott model are closer to the experimental values. From a materials perspective, on the other hand, the exciton binding energy of the melon is lower than that of PTI/Li+Cl−.

Purine-Doped g-C3N4-Modified Fabrics for Personal Protective Masks with Rapid and Sustained Antibacterial Activity.

Protective masks are critical to impeding microorganism transmission but can propagate infection via pathogen buildup and face touching. To reduce this liability, we integrated electrospun photocatalytic graphitic carbon nitride (g-C3N4) nanoflakes into standard surgical masks to confer a self-sanitization capacity. By optimizing the purine/melamine precursor ratio during synthesis, we reduced the g-C3N4 band gap from 2.92 to 2.05 eV, eliciting a 4× increase in sterilizing hydrogen peroxide production under visible light. This narrower band gap enables robust photocatalytic generation of reactive oxygen species from environmental and breath humidity to swiftly eliminate accumulated microbes. Under ambient sunlight, the g-C3N4 nanocomposite mask layer achieved a 97% reduction in the bacterial viability during typical use. Because the optimized band gap also allows photocatalytic activity under shadowless lamp illumination, the self-cleaning functionality could mitigate infection risk from residual pathogens in routine hospital settings. Both g-C3N4 and polycaprolactone demonstrate favorable biocompatibility and biodegradability, making this approach preferable over current commercially available metal-based options. Given the abundance and low cost of these components, this scalable approach could expand global access to reusable self-sanitizing protective masks, serving as a sustainable public health preparedness measure against future pandemics, especially in resource-limited settings.

Construction of 2D/2D BCNS/Ti3C2 heterojunction with boron-doped g-C3N4 and Ti3C2 MXene for enhanced photocatalytic water splitting

Graphitic carbon nitride (g-C3N4) has attracted great interest in photocatalytic water splitting. However, the poor photogenerated charge carriers transfer and the insufficient driving force for oxygen evolution reaction limit its practical application. In this work, boron-doped g-C3N4 nanosheets (BCNS) have been synthesized by calcining a mixture of g-C3N4 and NaBH4. The synthesized BCNS were then combined with Ti3C2 MXene using electrostatic self-assembly to construct a 2D/2D BCNS/Ti3C2 heterojunction. The resultant BCNS retained the original framework of g-C3N4, while the optimized band structure of BCNS induced prominently enhanced visible light absorption, accelerated charge carriers separation, and the increased driving force for water oxidation compared to pure g-C3N4. Density functional theory further proved that BCNS can enhance the driving force for photocatalytic O2 evolution. Moreover, the construction of 2D/2D face-to-face BCNS/Ti3C2 heterojunction was carried out to further enhance photocatalytic performance due to the intimate contact interface and the accelerated separation and transfer of photogenerated charge carriers. As a result, the 2D/2D BCNS/Ti3C2 hetrojunction exhibited a dramatically improved photocatalytic water-splitting performance compared to pristine g-C3N4. This integrated engineering strategy, involving non-metal element doping and 2D/2D heterojunction construction, might provide a unique paradigm for the rational design of efficient photocatalysts for photocatalytic water splitting.

Metallosalen modified carbon nitride a versatile and reusable catalyst for environmentally friendly aldehyde oxidation

The development of environmentally friendly catalysts for organic transformations is of great importance in the field of green chemistry. Aldehyde oxidation reactions play a crucial role in various industrial processes, including the synthesis of pharmaceuticals, agrochemicals, and fine chemicals. This paper presents the synthesis and evaluation of a new metallosalen carbon nitride catalyst named Co(salen)@g-C3N4. The catalyst was prepared by doping salicylaldehyde onto carbon nitride, and subsequently, incorporating cobalt through Schiff base chemistry. The Co(salen)@g-C3N4 catalyst was characterized using various spectroscopic techniques including Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Infrared Spectroscopy (IR), and Thermogravimetric Analysis (TGA). Furthermore, after modification with salicylaldehyde, the carbon nitride component of the catalyst exhibited remarkable yields (74–98%) in oxidizing various aldehyde derivatives (20 examples) to benzoic acid. This oxidation reaction was carried out under mild conditions and resulted in short reaction times (120–300 min). Importantly, the catalyst demonstrated recyclability, as it could be reused for five consecutive runs without any loss of activity. The reusable nature of the catalyst, coupled with its excellent yields in oxidation reactions, makes it a promising and sustainable option for future applications.

Temperature-dependent excitonic emission characteristics of highly crystallized carbon nitride nanosheets.

Highly-crystallized carbon nitride (HCCN) nanosheets exhibit significant potential for advancements in the field of photoelectric conversion. However, to fully exploit their potential, a thorough understanding of fundamental excitonic photophysical processes is crucial. Here, the temperature-dependent excitonic photoluminescence (PL) of HCCN nanosheets and amorphous polymeric carbon nitride (PCN) is investigated using steady-state and time-resolved PL spectroscopy. The exciton binding energy of HCCN is determined to be 109.26 meV, lower than that of PCN (207.39 meV), which is attributed to the ordered stacking structure of HCCN with a weaker Coulomb interaction between electrons and holes. As the temperature increases, a noticeable reduction in PL lifetime is observed on both the HCCN and PCN, which is ascribed to the thermal activation of carrier trapping by the enhanced electron-phonon coupling effect. The thermal activation energy of HCCN is determined to be 102.9 meV, close to the value of PCN, due to their same band structures. Through wavelength-dependent PL dynamics analysis, we have identified the PL emission of HCCN as deriving from the transitions: σ*-LP, π*-π, and π*-LP, where the π*-LP transition dominants the emission because of the high excited state density of the LP state. These results demonstrate the impact of high-crystallinity on the excitonic emission of HCCN materials, thereby expanding their potential applications in the field of photoelectric conversion.&#xD.

Ultrasensitive detection of Ag+ and Ce3+ ions using highly fluorescent carboxyl-functionalized carbon nitride nanoparticles.

The fluorescence quenching of carboxyl-rich g-C3N4 nanoparticles was found to be selective to Ag+ and Ce3+ with a limit of detection as low as 30 pM for Ag+ ions. A solid-state thermal polycondensation reaction was used to produce g-C3N4 nanoparticles with distinct green fluorescence and high water solubility. Dynamic light scattering indicated an average nanoparticle size of 95 nm. The photoluminescence absorption and emission maxima were centered at 405 nm and 540 nm respectively which resulted in a large Stokes shift. Among different metal ion species, the carboxyl-rich g-C3N4 nanoparticles were selective to Ag+ and Ce3+ ions, as indicated by strong fluorescence quenching. The PL sensing of mixtures of Ag+/Ce3+ and Ce3+ followed static Stern-Volmer kinetics with the Stern-Volmer constants determined to be 74.18 ×10^3 M-1 and 27.2 ×10^3 M-1 respectively. The PL sensing of Ag+ followed modified Stern-Volmer kinetics. Sensing was also demonstrated using commercial filter paper functionalized with g-C3N4 nanoparticles, enabling practical on-site applications.&#xD.

Construction of Phosphorus‐Doped g‐C3N4 Nanosheets and Activation of Sodium Percarbonate for Degradation of Organic Pollutants in Wastewater

AbstractA novel phosphorus‐doped graphitic carbon nitride nanosheets (PS‐CN) photocatalyst was prepared by thermal polycondensation and thermal stripping method, and its physicochemical properties were characterized. The results show that PS‐CN formed a thin sheet and multi‐cavity structure by thermal delamination that could enhance the surface area, light reception, and adsorption capacity. The prepared PS‐CN activated sodium percarbonate system (PS‐CN/SPC) was developed for the degradation of dyeing wastewater with methylene blue (MB) as the target pollutant and the degradation mechanism was analyzed. At room temperature (20 °C), the degradation rate of MB in PS‐CN/SPC system within 10 min (88.13 %) was three times that of pure g‐C3N4. In addition, the MB was completely degraded under visible light within 60 min. Moreover, PS‐CN exhibited excellent reusability that the degradation rates of MB have remained above 96 % in five consecutive cycles. The free radical quenching experiments showed that hole (h+), hydroxyl radical (•OH) and superoxide radical (•O2−) all participated in MB degradation, and •OH was the main active species. The PS‐CN/SPC system would provide a high‐value solution for the treatment of dye wastewater due to the low cost of raw materials, superior photocatalytic activity, simple synthesis method, and reusability of the catalyst.

Visible-Light-Induced Anionic Photopolymerization of Ethyl-2-cyanoacrylate with Graphitic Carbon Nitride

Visible-Light-Induced Anionic Photopolymerization of Ethyl-2-cyanoacrylate with Graphitic Carbon Nitride

Template-free synthesis of hierarchical graphitic carbon nitride (H-gC3N4) embedded with NiO for water splitting and CO2 reduction with the role of hole scavenger: A comparative investigation

Hierarchical graphitic carbon nitride (H-gC3N4) embedded with nickel oxide (NiO) were synthesized using a template-free hydrothermal approach. The performance of NiO/H-gC3N4 composite was investigated for photocatalytic water splitting in a slurry system to produce H2. Similarly, photocatalytic CO2 reduction to generate CO under visible light was conducted in a gas-phase photoreactor system. Optimized 2% NiO/H-gC3N4 composite enables H2 production of 1010 μmol g−1 h−1, which was 13.93 folds higher than using pure H-gC3N4. Similarly, the highest CO evolution rate of 96.7 μmol g−1 h−1 was obtained, 3.85 folds higher than using H-gC3N4. The enhanced photoactivity resulted mainly from the distinctive interlayer structure, improved light penetration, reduced charge carrier recombination and increased surface-reactive active sites. The methanol sacrificial reagent, owing to its capacity to generate extra protons, proved pathways in augmenting the yields of both H2 and CO. While the efficiency of water splitting for H2 production surpassed that of CO2 reduction, it exhibited lower stability. The recently developed composite demonstrated consistent and sustained photocatalytic efficiency for CO production throughout five consecutive cycles.

Fabrication of DDP-functionalized carbon nitride nanosheets via thiol-ene “click” reaction as lubricant additives

Herein, the functionalized graphite carbon nitride (DDP@g-C3N4) nanosheets were successfully prepared via the surface self-assembly method combined with “click” reaction. Firstly, the 3-(trimethoxysilyl) propyl acrylate (TOPA) was self-assembled onto the g-C3N4 surface to obtain TOPA@g-C3N4, then the dialkyl dithiophosphate (DDP) was grafted onto TOPA@g-C3N4 via thiol-ene “click” reaction formation of DDP@g-C3N4. The load-carrying capacity of PAO10 is increased to 900 N from 200 N with 1.5 wt% DDP@g-C3N4 addition, and the average COF decreased from 0.17 to 0.10, accompanied by a 96.7 % decrease in wear volume. This improved lubricating performance is attributed to the formation of a continuous protective film including iron oxides, iron sulfide, and iron phosphate via tribochemical reactions, which prevent direct contact and seizure between friction pairs.

Defect Engineering Simultaneously Regulating Exciton Dissociation in Carbon Nitride and Local Electron Density in Pt Single Atoms Toward Highly Efficient Photocatalytic Hydrogen Production.

The high exciton binding energy (Eb) and sluggish surface reaction kinetics have severely limited the photocatalytic hydrogen production activity of carbon nitride (CN). Herein, a hybrid system consisting of nitrogen defects and Pt single atoms is constructed through a facile self-assembly and photodeposition strategy. Due to the acceleration of exciton dissociation and regulation of local electron density of Pt single atoms along with the introduction of nitrogen defects, the optimized Pt-MCT-3 exhibits a hydrogen production rate of 172.0µmolh-1 (λ ≥ 420nm), ≈41 times higher than pristine CN. The apparent quantum yield for the hydrogen production is determined to be 27.1% at 420nm. The experimental characterizations and theoretical calculations demonstrate that the nitrogen defects act as the electron traps for the exciton dissociation, resulting in a decrease of Eb from 86.92 to 43.20meV. Simultaneously, the stronger interaction between neighboring nitrogen defects and Pt single atoms directionally drives free electrons to aggregate around Pt single atoms, and tailors the d-band electrons of Pt, forming a moderate binding strength between Pt atoms and H* intermediates.

The heptazine-based materials through intrinsically modification for the cycloaddition of CO2 and bisepoxides.

For the efficient utilization of CO2 into valuable product, the attractive carbon nitride catalysts have been widely studied. In this work, heptazine-related materials with varying degree of polymerization were designed by an intrinsically modification strategy and employed in the cycloaddition of CO2 with the bisepoxide 1, 4-butanediol diglycidyl ether (BDODGE). We initially figured out that the sample prepared at 450°C contained more melem hydrate, exhibiting the best performance. The epoxides conversion and corresponding cyclic carbonates selectivity could achieve 93.1% and 99.3% at 140°C for 20 h without any cocatalyst and solvent, respectively. Results of the catalytic tests suggested that the high catalytic activity was dependent on big size porous structure and the synergetic effect of active amino groups and -OH groups. The role of water in maintaining the specific structure and providing active site has been proved. Moreover, the CN-450-W catalyst exhibited outstanding recycling stability. And finally, a plausible reaction mechanism was proposed.

Optimizing light-driven ene-reductase reactions with g-C3N4 and electron mediators

In the realm of green chemistry and sustainable industrial processes, the integration of enzymes with photocatalytic materials offers a promising avenue for achieving efficient, light-driven catalysis while minimizing environmental impact. This study introduces an enzyme-photo-coupled catalytic system (EPCS) using graphitic carbon nitride (g-C3N4) as a photocatalyst and methyl viologen (MV2+) as an electron mediator to drive the reduction of 2-cyclohexen-1-one by the Old Yellow Enzyme (OYE), reducing the reliance on expensive and scarce bioelectronic carriers and demonstrating a sustainable alternative for biocatalytic applications. Furthermore, we explored the incorporation of a Pickering emulsion system to enhance mass transfer, especially in reactions involving highly concentrated substrates. This adaptation not only improves the yield of the EPCS at higher substrate concentrations but also offers a scalable and environmentally benign alternative to traditional photocatalytic systems.

Peroxymonosulfate Activation by Bi-Fe Oxide Co-Doped Graphitic Carbon Nitride for Degradation of Sulfamethoxazole: Performance and Mechanism

Graphite carbon nitride (g-C3N4) has been employed as an emerging metal-free catalyst in heterogeneous catalysis. However, the catalyst has a poor activation property for peroxymonosulfate (PMS). In this study, Bi-Fe oxide co-doped g-C3N4 (Bi@Fe/CN) was synthesized for PMS activation to degrade sulfamethoxazole (SMX). In particular, Bi@Fe/CN-3 presented remarkable catalytic performance with 99.7% removal of SMX within 60 min in the PMS system. Additionally, Bi@Fe/CN-3 presented good stability and recyclability through the cycling experiments. Moreover, it was shown that free radicals (O2•−, •OH, and SO4•−) and non-free radicals (1O2) were the primary active species in the Bi@Fe/CN-3/PMS system. Bi, Fe, and surface lattice oxygen were confirmed to be the main contributors to the active species. This work elucidates the mechanism of activation of PMS by Bi@Fe/CN-3, which is beneficial to promote the application of bimetallic oxide-modified g-C3N4/PMS systems in wastewater treatment.

Friction‐Reducing and Anti‐Wear Mechanism of BP/Nano‐Fe3O4 Nanocomposite as a Lubricant Additive in Soybean Oil

ABSTRACTAs an emerging two‐dimensional material, black phosphorus (BP) has excellent tribological properties, but the poor dispersion of BP in oil inhibits its application in friction to some extent. Surface modification is one of the effective methods to solve the dispersibility of BP, and the use of nano‐Fe3O4 dotted on the surface of BP improves the dispersion stability of BP in soybean from 3 days to about 15 days. Compared with pure soybean oil, friction coefficient and wear rate of the addition of 0.12 wt% BP/Fe3O4 are reduced 65% and 78%, respectively. To elucidate the excellent tribological mechanisms of BP/Fe3O4 as additives in soybean oil, the compositional and structural characterisation of the abrasion mark surface was studied accordingly. On the one hand, soybean oil reacts with BP/Fe3O4 to form a composite tribo‐film during the scraping process. This tribo‐film composed of amorphous carbon, iron oxide and phosphorus oxide nitrides prevents direct contact between the sliding interfaces. On the other hand, BP and Fe3O4 nanoparticles form a mechanical rollerball structure, which can further reduce interfacial friction and wear through synergistic lubrication. The results provide new insights into the design of additives in biomass lubricating oils and propose new application prospects for BP in the field of lubricating additives.

Polydopamine Modified Carbon Nitride and PAMAM Assembled Electrochemical Immunosensor for Detection of Indole‐3‐Acetic Acid

AbstractIndole‐3‐acetic acid (IAA) assumes a pivotal role as a phytohormone of utmost importance, intricately orchestrating the nuanced processes associated with the growth and developmental trajectories of botanical organisms. In this study, we have designed and fabricated a label‐free electrochemical impedance immunosensor for the precise detection of IAA. The detection strategy predominantly relied upon polydopamine modified carbon nitride (C3N4) nanosheets (PCN) and polyamidoamine (PAMAM) dendrimer. Through the modification with PCN and PAMAM, the electrode has increased the active area and enhanced the immobilization capacity of antibodies for IAA. The immunosensor‘s ability to capture IAA was significantly improved by enhancing the immunoreaction between the antibody and antigen. This enhancement led to an increased response in the electrochemical behavior of the Fe(CN)63−/4− redox probe. The impedance immunosensor developed exhibits remarkable sensitivity, exceptional selectivity, and consistent performance in the detection of IAA. This assay method, with the potential to replace antibodies, could offer an alternative approach for detecting various phytohormones.