CN Materials Research Articles

Efficient and stable photocatalytic degradation of triazophos pesticides by g-C3N4/WO2.72 nanocomposite with S-scheme heterojunction and oxygen vacancies

Facing the increasingly severe issue of organophosphorus pesticide contamination globally, this study has developed a novel g-C3N4/WO2.72 nanocomposite (abbreviated as CN/WO), featuring a specially designed S-scheme heterojunction and oxygen vacancies, to optimize the photocatalytic degradation of triazophos pesticides. Experiments demonstrate that the composite containing 30 % CN (termed 30-CN/WO) can efficiently degrade most of the triazophos within 100 minutes, and it exhibits exceptional stability across four successive cycles, significantly outperforming the individual CN and WO materials. Advanced analytical techniques such as X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and surface work function assessments have confirmed the pivotal role of the S-scheme heterojunction and oxygen vacancies in enhancing charge separation efficiency. This work not only advances the development of high-performance photocatalytic materials but also provides new strategies and practical scientific evidence for addressing organophosphorus pesticide pollution globally, showcasing its broad application prospects and scientific significance in environmental management.

Thermal recombination strategy designed R-CN as active shell to improve catalyst activity

A new recombinant CN material (R-CN) was prepared with g-C3N4 as precursor by hydrothermal method combined with thermal recombination method, which has 2D ultra-thin structure, nanoscale folds, graphite-like texture and some pores, and has richer N and O elements than g-C3N4. R-CN can reduce high temperature decomposition peak of ammonium perchlorate (AP) to 356.06 oC, and its promoting effect is obviously better than that of g-C3N4. Based on specific structural composition and physicochemical properties of R-CN, a novel R-CN@MWO composite with core-shell was designed, which was applied to catalytic decomposition of AP and pressure enlarging effect during combustion process of cyclotrimethylenetrinitramine (RDX)+nitrocellulose (NC). With the introduction of R-CN@MWO, decomposition peak temperature and activation energy of AP are reduced by 104.67oC and 59.24 kJ mol−1, and peak pressure and pressurization rate of RDX+NC constant volume combustion test are increased by 11.33 and 118.54 times, respectively. Moreover, the combustion rate of R-CN@MWO-AP/HTPB propellant is 3.23 times that of AP/HTPB propellant. To sum up, R-CN as a coating layer can significantly enhance catalytic activity of MgWO4 for thermal decomposition of energetic materials.

Fluorescent Composite Cotton Fabric Modified with Crosslinked Chitosan for Theranostic Applications

Developing multifunctional textile material for wound dressing is challenging due to the variety of wounds and their differing healing stages. Therefore, theranostics replaces the traditional approach to provide patient comfort and accelerated healing. In this study, we developed and compared three different materials. For this purpose, for the first time, chitosan was modified with 4-nitro-1,8-naphthalic anhydride in N,N-dimethylformamide (DMF) suspension, and subsequent nucleophilic substitution of the nitro group with N,N-dimethylamino group, whereby chitosan with a yellow color and fluorescence was obtained. Cotton fabric was impregnated successively with a citric acid solution and solution from chitosan and chitosan modified with 1,8-naphthalimide fluorophore (CN material). The same experimental protocol was applied for the second material, but indomethacin was added to the chitosan solution (CNI material). The third material was prepared similarly to the second but was immersed in an alginate solution as a last step (CNIA material). The obtained materials have been characterized by optical and scanning electron microscopy and thermal analysis (TG-DTA-DTG). Indomethacin release from composite materials and hydrogel swelling and erosion in phosphate buffer pH 7.4 at 37 °C was examined using gravimetric analysis, UV-vis absorption, and fluorescence spectroscopy. The antimicrobial activity of the cotton samples has been evaluated against B. cereus and P. aeruginosa as model bacterial strains. The analysis showed that CN material inhibited about 98.8% of the growth of P. aeruginosa and about 95.5% of the growth of B. cereus. Other composite materials combine antimicrobial properties with a sustained release of biologically active substances that can observed visually.

Cyano-rich carbon nitride with tunable n → π* electronic transition for enhanced broad-spectrum photocatalytic H2O2 production

The development of photocatalysts that effectively utilize broad-spectrum light, which occupies a primary percentage of the solar spectrum, remains a great challenge. In this paper, we propose a salt-assisted method mediated by sodium oxalate template to achieve both oxygen doping and formation cyano group defects in carbon nitride materials (CNNO). The simultaneous introduction of oxygen and cyano defects not only induced the distortion of the heptazine structure thus effectively activated the n → π* electron transition, but also can achieve the qualitative changes of broad-spectrum photocatalytic H2O2 production from “0″ to “1” (λ ≥ 700 nm) of CNNO, which has rarely been reported in single photocatalysts. DFT calculations show that the electronic structure of CNNO is rearranged to favor O2 adsorption as well as the formation of the key intermediate OOH*. The present work achieves the co-optimization of electronic structure and light absorption of CN through the synergistic effect of oxygen doping and the construction of cyano defects, which provides a new strategy for the design and synthesis of CN materials that effectively utilize sunlight.

Synthesis of prussian blue analogue derived porous Mo2C/Co9S8/N-doped carbon composite for electrochemical hydrogen storage application

The Prussian blue analogue Co3[Co(CN)6]2 (Co-CoPBA) nanoparticles with three-dimensional cubic structure and uniform size were prepared via precipitation method. Using Co-CoPBA as the precursor, the porous Co9S8/N-doped carbon (Co9S8–CN) nanostructure was formed after heat treatment and sulfidation processes. To further improve the electrocatalytic activity of the composite, Mo2C was introduced within the porous Co9S8–CN. The Mo2C/Co9S8–CN materials containing different contents of Mo2C were prepared via high-temperature calcination and subsequent sulfidation. Ultimately, for electrochemical hydrogen storage, the porous Co9S8–CN exhibited higher discharge capacity than conventional Co9S8 prepared by hydrothermal method. The special porous structure and large specific surface area derived from Co-CoPBA provided more electrochemical active sites. The conductivity of Co9S8 was enhanced due to the existence of N-doped carbon. Additionally, the electrochemical performance further enhanced owing to the excellent electrocatalytic activity of the embedded Mo2C species. The Mo2C/Co9S8–CN2 electrode showed an optimum discharge capacity of 647.4 mAh/g. Moreover, the high-rate dischargeability (HRD), corrosion resistance and kinetic properties were also improved after Mo2C loading. Consequently, Mo2C/Co9S8–CN can be used as a potential electrochemical hydrogen storage material.

Enhanced Visible-Light-Driven Photocatalytic Activity by Fe(Ш)-Doped Graphitic C3N4.

Fe(Ш)-doped graphitic carbon nitride (Fe(Ш)-CN) photocatalysts with various Fe(Ш) ions content were prepared via ultrasonic method. Detailed physical characterization indicated that Fe(Ш) ions had been successfully doped into the frame of g-C3N4. The photocatalytic activities were investigated, and methyl orange (MO) and tetracycline hydrochloride (TC) were used as the targeted pollutants. The as-prepared Fe(Ш)-CN materials exhibited higher photocatalytic activities than those of the pure g-C3N4. Specifically, the degradation rate of 2Fe(Ш)-CN under visible light was 2.06 times higher for MO and 2.65 times higher for TC than that of g-C3N4. The increased photocatalytic activities of Fe(Ш)-CN were mainly attributed to the enhanced light absorption ability and the rapid separation of photogenerated carriers. Moreover, the importance of active species during the reaction process was also explored, and the results indicated that •O2− is the main active species.

Template-based textural modifications of polymeric graphitic carbon nitrides towards waste water treatment.

The composite materials based on graphitic carbon nitrides (g-C3N4) are remarkably better semiconductors, but the inherent photocatalytic performance in its generic synthesis form is not up to the mark. Eminence efforts have been made to improve its performance and photocatalytic efficiencies. Recently, extensive investigations have been performed to develop their texturally modified and highly porous structures to get around the big flaws of bulk g-C3N4. One significant disadvantage is the increase in the polycondensation while preparation at 550°C results in g-C3N4 materials with restricted specific surface area (SSA) (<10m2/g) and no textured pores. Textural modification has emerged as an efficient and progressive way to improve optical and electronic characteristics. The final texture and shape of CN are influenced by the precursor's interaction with the template. Researchers are interested in developing CN materials with high SSA and changeable textural properties (pore volume and pore size). Based on the literature review it is concluded that the soft templating approach is relatively simple, and straightforward to induce textural changes in the g-CN type materials. This review focused on improving the textural properties of bulk g-C3N4 via templating method, and the major advances in the modified g-C3N4 materials for the treatment of wastewater. The procedures and mechanisms of numerous approaches with varying morphologies are thoroughly explained.

Hydroxy-Modified Hierarchical Porous Na-CoOx /CN Material for Low-Concentration High-Throughput Formaldehyde Oxidation at Room Temperature.

Engineering the pore structure and surface properties of the catalyst are the key to realizing the highly efficient conversion of low-concentration and high-throughput formaldehyde at room temperature. Herein, alkali-modified hierarchical porous Na-CoOx /CN material was prepared using a novel freeze-drying-pyrolysis method by employing super absorbent resin/MOF composites as templates, which generate mesopores distributed in a narrow region of 6∼20 nm and abundant hydroxyl groups on the surface by alkali-modification. At room temperature, the Na-CoOx /CN material exhibited full conversion of low concentration (1.0 mg/m3 ) and high throughput (240,000 mL/(gcat h)) formaldehyde while also demonstrating outstanding catalytic stability under a even higher space velocity (480,000 mL/(gcat h)). In situ DRIFTS characterization revealed that the hydroxyl groups on the catalyst's surface could be consumed by oxidizing formaldehyde to intermediate species (carbonate, hydrocarbonate), which were then regenerated by Na+ and CO3 2- , contributing to the cycle of the reaction path.

G-C3N4/BiOI S‑scheme heterojunction: A 2D/2D model platform for visible-light-driven photocatalytic CO2 reduction and pollutant degradation

Photo-degradation of pollutant and photo-reduction of CO2 are efficient ways to address challenges of water pollution, the greenhouse effect and energy crisis, respectively. In our work, via fastening two-dimensional (2D) BiOI nanoplates on 2D g-C3N4 nanosheets, a BiOI/g-C3N4 (BI/CN) S-scheme photocatalyst with closely stacked structure were prepared though a self-assembly process. The prepared BI/CN S-scheme heterojunction could improve the transfer and separation efficiency of photo-generated electron-hole pairs by facilitating the electrons transfer from BiOI to g-C3N4. Under visible light exposure, the photo-degradation efficiencies of tetracycline hydrochloride (TC) and p-chlorophenol (4-PC) by BI/CN-50% reached nearly 100% and 46%, respectively, which were more excellent in comparison with other samples. And BI/CN-50% sample exhibited the best CO production (12.45 μmol∙g−1) with visible-light irradiation of 4 h. This value was approximately 4.37 and 5.41 times higher than that of BI (2.85 μmol∙g−1) and CN materials (2.30 μmol∙g−1), respectively. Moreover, the excellent photocatalytic performance had no visible decay during five cycles. Meanwhile, an S-scheme charge transfer process was confirmed by species trapping experiments and electron spin-trap analysis. This study offers new insights into the activity, kinetics, and mechanism over BiOI-based materials for photocatalysis technology.

A Minireview on the Use of g-C3N4–Chitosan Biocomposite for Potential Applications

The novel biocomposite based on graphitic carbon nitride (g-C3N4 (CN)) and Chitosan (CS) has been deeply studied and summarized in key points concerning various applications. The CN material is composed of the earth-abundant nature of C, N, and H and possesses excellent properties due to its two-dimensional structure, good chemical stability, and a narrow bandgap that allows its use in many applications. There is a lot of information on the role of CN as a potential photocatalyst, but not in association with other composites. In contrast, this minireview summarizes its applications not only in the field of photocatalysis but also in all fields reported on the biocomposite of CN with CS. The incorporation of chitosan helps to overcome the existing limitations of CN, like low-surface area, low light absorption, fast recombination of charges, and hydrophobic character. To introduce, CS is an attractive biomaterial, which is a low-cost alternative for the preparation of films and catalysts due to its unique characteristics such as biodegradability, antimicrobial activity, and film-forming properties that increase the popularity of CN. In this current minireview, a comprehensive study was conducted on the properties, synthesis, and applications along with the advancements of CN incorporated with CS. Finally, we hope to stimulate researchers to study the biocomposite of CN and CS to find new portals and ways to develop effective materials.

Theoretical study on the synthesis of vinyl acetate from acetylene and acetic acid over nonmetallic catalysts with different carbon-nitrogen ratios

At present, the acetylene acetic acid reaction catalysts studied are metal catalysts. Whether there are non-metallic materials that can catalyze the reaction is very worth exploring. In this study, we used density functional theory (DFT) to calculate the feasibility of preparing vinyl acetate (VAc) on four CN non-metallic materials (C2N, C3N, C4N and C5N) under the reaction conditions of 1 atm, 393.15–493.15 K at B3LYP/6-31G(d, p) level. It is found that after considering the reaction temperature, only C2N and C3N show good adsorption capacity for acetylene and acetic acid, and C3N has stronger adsorption capacity for reactants. After that, we calculated and simulated the reaction process of acetylene acetic acid reaction catalyzed by four CN materials. It is found that among the four CN materials, the energy barrier of the reaction rate control step of C3N is the lowest (the free energy barrier of the rate control step is only 30.57 kcal/mol at 393.15 K), and the interior of CN non-metallic materials has higher activity than the boundary of hydrogen sealing. We also found that the reaction process on CN non-metallic material is consistent with the acid catalysis mechanism, which shows that the non-metallic catalyst is theoretically feasible for catalyzing the acetic acid acidification of acetylene, and the two-dimensional C3N material is likely to be a potential non-metallic catalyst for the preparation of vinyl acetate by acetylene gas phase method.

New insights into the exploitation of oxidized carbon nitrides as heterogeneous base catalysts

In this work, the development of a novel efficient heterogeneous catalytic system capable of driving Knoevenagel condensation reactions between benzaldehydes and malononitrile was reported. Specifically, we explored a post-synthetic modification of graphitic carbon nitride (g-CN) through a strong oxidation treatment by acid mixture (HNO3/H2SO4). The as-prepared oxidized CN material (CNO) shows a large number of surface acidic moieties, that can be easily deprotonated through an aqueous alkaline wash with different bases (NaOH, K2CO3, t-BuOK), to introduce a high density of reactive basic sites. The best catalyst is obtained with NaOH as the base (CNO-NaOH), and displays high reactivity and good tolerance towards functional group variations of the reagents, thus emerging as a potential new recyclable carbon nitride-based structure for organic base catalysis.

Carbon nitride materials: impact of synthetic method on photocatalysis and immobilization for photocatalytic pollutant degradation

Different synthesis routes for carbon nitride materials (CN) and the resulting products were compared to study the photocatalytic activity (pollutant degradation) in dependence on structure and properties. The CN materials were synthesized by thermal decomposition of dicyandiamide in air and under argon as well as in sealed ampoules with or without the use of a salt melt. The as-prepared materials were characterized by IR spectroscopy, nitrogen adsorption measurement, solid-state NMR spectroscopy, diffuse reflectance UV–Vis spectroscopy, elemental analysis and powder X-ray diffraction (PXRD). The surface polarity of the CN materials was estimated by adsorption of the dicyano-bis(1,10-phenanthroline)-iron(II) complex, which allows an evaluation of the degree of condensation. The CN materials were tested with regard to the photocatalytic degradation of rhodamine B (RhB). It is shown that the photocatalytic activity increases with higher surface polarity. Promising CN materials with high RhB degradation of 85% within 25 min and high surface polarity of 0.89 were selected for an immobilization approach to obtain coatings on a silicone substrate using a high-volume low-pressure (HVLP) spray coating technique. To study the photocatalytic activity of the catalyst coatings, the degradation rates of an aqueous RhB solution and solutions of organic pollutants such as triclosan and ethinyl estradiol were examined. Pollutants are decomposed with up to 63% of the initial concentration. Xenon lamps and different LEDs were used as light sources for comparison. Particularly high degradation efficiencies were obtained using LEDs, and the degradation rates are increased by adjusting the emission spectrum of the lamp to the pollutant and absorption edge of the catalyst, which results in a 40 times higher degradation efficiencies of LEDs compared to a Xe lamp.Graphical abstract

Fluorescent Carbon Nitride Macrostructures Derived from Triazine‐Based Cocrystals

AbstractCarbon nitride (CN) based materials have emerged as efficient photo‐ and electrocatalysts for various reactions. However, despite their intriguing optical properties (i.e., fluorescence), their utilization as solid‐state sensing platforms remains in its infancy, owing to the formation of defect states during the materials synthesis, leading to low emission for the CN powder. Here, a bottom‐up synthesis of CN macrostructures with good photoluminescence properties in both liquid and solid state is introduced, from designed triazine‐based cocrystals with ordered morphology and tailored chemical composition. Upon calcination at 500 °C, the starting morphology and chemical composition are retained, resulting in the alteration of the HOMO‐LUMO distribution of the CN materials, as further supported by density functional theory (DFT) calculations. The good photoluminescence properties of the new CN materials enable their exploitation as environmentally friendly, robust, and cheap sensing material for latent fingerprints labeling and metal‐ion detection in water.

Doping of graphitic carbon nitride with oxygen by means of cyanuric acid: Properties and photocatalytic applications

Bare and oxygen doped graphitic carbon nitride were synthetized by the thermal polymerization of melamine (CN-M) and the mechanical mixtures of melamine and cyanuric acid, respectively, at 550 °C for 4 h. The ratios of melamine and cyanuric acid were 1:0.5, 1:1 and 1:2 (CN-MCA1, CN-MCA2 and CN-MCA3). The content of oxygen increased from 1.88 wt% (CN-M) to 3.93 wt% (CN-MCA3) and the specific surface area increased from 14 to 41 m2 g−1. The prepared CN materials were characterized by the elemental analysis, UV-Vis diffuse reflectance, X-ray diffraction, Fourier transform infrared spectrometry, the physisorption of nitrogen, scanning electron and high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, the determination of zeta potentials, and the Mott-Schottky method.The addition of cyanuric acid led to partial changes in the CN morphology, as documented by occurrence of CN tubes, increase in the specific surface area and was a source of additional -O- and -OH moieties which modified the CN surface in addition to the spontaneous oxygenation observed in CN-M. The above effects positively influenced photocatalytic activity of the CN materials as demonstrated using Rhodamine B (RhB) and the Ofloxacin antibiotics. The photocatalytic decomposition of Ofloxacin was more efficient than that of RhB and differed in kinetics (first-order vs. zero-order reaction). The reusability and stability of the CN materials was verified by repeating batch photocatalytic decompositions of Ofloxacin experiments for five times.

Comparison of Graphitic Carbon Nitrides Synthetized from Melamine and Melamine-Cyanurate Complex: Characterization and Photocatalytic Decomposition of Ofloxacin and Ampicillin.

Graphitic carbon nitride (g-C3N4, hereafter abbreviated as CN) was prepared by the heating of melamine (CN-M) and melamine-cyanurate complex (CN-MCA), respectively, in air at 550 °C for 4 h. The specific surface area (SSA) of CN-M and CN-MCA was 12 m2 g−1 and 225 m2g−1 and the content of oxygen was 0.62 wt.% and 1.88 wt.%, respectively. The band gap energy (Eg) of CN-M was 2.64 eV and Eg of CN-MCA was 2.73 eV. The photocatalytic activity of the CN materials was tested by means of the decomposition of antibiotics ofloxacin and ampicillin under LED irradiation of 420 nm. The activity of CN-MCA was higher due to its high SSA, which was determined based on the physisorption of nitrogen. Ofloxacin was decomposed more efficiently than ampicillin in the presence of both photocatalysts.

G-C3N4 nanosheets adhered with Ag3BiO3 and carbon dots with appreciably promoted photoactivity towards elimination of several contaminants

Herein, graphitic carbon nitride nanosheets (signified as CN-NS) were anchored with Ag3BiO3 and carbon dots (abbreviated as CDs) by hydrothermal procedure with appreciably promoted photoactivity towards elimination of several contaminants. The CN-NS/CDs/Ag3BiO3 (30%) system, as optimal photocatalyst, demonstrated extremely high elimination efficiency for several pollutants such as methylene blue (MB), malachite green (MG), Rhodamine B (RhB), and methyl orange (MO) under visible light, which is 55.5, 36.5, 39.2, and 32.1 folds premier than CN material, respectively. Besides, PL, EIS, and transient photocurrent response data corroborated that the CN-NS/CDs/Ag3BiO3 (30%) material has the highest charge carriers segregation efficiency compared with the pure and binary systems. Energy band structure analysis demonstrated that the improved performance of CN-NS/CDs/Ag3BiO3 photocatalyst is allocated to Z-scheme heterojunction. Scavenging tests demonstrated that h+, •OH, and •O2− are the crucial species in the RhB degradation. Enhancement of elimination ability can be allocated to more generation of the charge carries and improvement of the segregation rate of them promoted through the Z-scheme mechanism.

Anomalous phonon softening of G-band in compressed graphitic carbon nitride due to strong electrostatic repulsion

Graphitic carbon nitride (C2N and C3N) with various π electron distributions on layers have been studied under pressure through a combined theoretical and experimental approach and a comparison with graphite. It is found that as these materials transform into low compressibility phases in the pressure range from 15 to 45 GPa, strong electrostatic repulsion between π electrons and in-plane sp2 electrons may distort and soften the sp2 bonds, leading to anomalous pressure evolutions of the intralayer phonon vibrations, such as a plateau-like behavior of E2g mode (G-band) in C2N and C3N. This also causes a slow increase in the resistivity/resistance of C2N and C3N as pressure increases, and the gradual interlayer bonding leads to an abrupt increase in resistance of the materials but with different pressure responses due to their different π electron distributions. Moreover, the intensity enhancement of the G band in both CN materials may be related to their electronic structure changes. The results deepen our understanding of the effects of π electron distribution on the structural transition of graphitic materials and may explain some unexplained in previous studies.

Nanoporous carbon nitride with a high content of inbuilt N site for the CO2 capture

We report the nanoconfinement-mediated graphitic nanoporous carbon nitride (gNPCN) adsorbents with a high content of inbuilt basic nitrogen (N) (48%) by X-ray photoelectron spectroscopy (XPS) for efficient CO2 adsorption. The gNPCNs (gNPCN-150 and gNPCN-130) are synthesized using the mesoporous SBA-15 silica template and a single carbon-nitrogen (C–N) precursor (guanidine hydrochloride). The various adsorbents were utilized for investigating the influence of pore size (PS), surface area (SA), and type of adsorbent for CO2 adsorption performance. The capacity for CO2 capturing of gNPCN-150 reached 23.1 mmol/g at 0 °C under 30 bar pressure. This CO2 capturing capacity value was higher than the capacity gNPCN-130, SBA15, activated carbon (AC), and multiwalled carbon nanotube (MWCN) under identical conditions. The gNPCN materials exhibited superior CO2 adsorption ability that is ascribed to the presence of the highly organized mesoporosity, inbuilt high content of basic N site for adsorbing more CO2 through acid-base interaction, and tunable surface-structural properties. Moreover, the synthesis strategy is remarkably flexible in selecting C–N sources. This study features graphitic high-ordered nanoporous CN materials as a resourceful platform towards the efficient CO2 capture.

Theoretical and experimental study of full spectrum response Z-scheme 0D/2D Ag6Si2O7/CN photocatalyst with enhanced photocatalytic activities

Herein, we reported a Z-scheme 0D/2D Ag6Si2O7/CN composite photocatalyst via simple precipitation method, where the electron structure and optical properties of Ag6Si2O7 and CN materials were studied by theoretical computation. The XPS, TEM, radical trapping experiments and ESR measurement results illustrated the formation of the Z-scheme 0D/2D Ag6Si2O7/CN heterostructure. The crystal structure and surface composition of the prepared materials were characterized by XRD, SEM and FT-IR. The UV–vis DRS, PL, I-t, and EIS demonstrated that all composites have improved light absorption ability and enhanced photo-generated charge separation rate. The construction of 0D/2D Ag6Si2O7/CN Z-scheme heterojunction is helpful to improve photodegradation ability, which can not only enhance the separation and transmission efficiency of the photogenerated carriers, but also retain the strong redox ability of photocatalysts. This paper provides a novel comprehension of the mechanism of Z-scheme composites by combining theoretical calculations and experiments.