Graphite-like Carbon Nitride Research Articles

Preparation of New Hybrid Materials SiO2@Melamine-Cyanurate as Precursors of Graphite-Like Carbon Nitride

This work describes the use of silica particles obtained by sol-gel method as a templat for deposition of supramolecular complexes of melamine cyanurate. To obtain SiO2@melamine-cyanurate (SiO2@MCA) material, the method of covalent modification of silica surface by melamine molecules (SiO2-mel) was applied and the method of its further functionalization by hydrogen-bonded organic framework of melamine-cyanurate (HOF, MCA) was proposed. One of the promising directions of using SiO2@melamine-cyanurate is obtaining SiO2@g-C3N4 material on its basis. Control of the amount of applied melamine-cyanurate allows to potentially obtain g-C3N4 layers of different thicknesses on the silica surface.

Photocatalytic Activity of Heterostructures Based on Graphite-Like Carbon Nitride Modified with Few-Layer Black Phosphorus and Cobalt Phosphide in the Hydrogen Evolution Reaction

Photocatalytic Activity of Heterostructures Based on Graphite-Like Carbon Nitride Modified with Few-Layer Black Phosphorus and Cobalt Phosphide in the Hydrogen Evolution Reaction

From aromatic rings to aliphatic compounds - degradation of duloxetine with the use of visible light driven Z-scheme photocatalyst

The growing consumption of antidepressants, associated with their high chemical stability and low biodegradability, become a serious problem for aquatic environment. Many of their components are resistant to conventional water treatment technologies. The photocatalytic processes with the use of semiconductors becoming attractive methods of drugs degradation because the highly reactive species: electrons, holes, hydroxyl radicals (⦁OH) and superoxide anion radicals (O2⦁−) generated under illumination may be involved directly or indirectly in decomposition of complicated organic molecules.In this work we have shown for the first time that Z-scheme photocatalyst, consisted of bismuth vanadate (BiVO4), graphitic-like carbon nitride (g-C3N4) and Au nanoparticles (Au NPs) as a charge transfer mediator, is very efficient in degradation of duloxetine (DLX). We performed the comprehensive evaluation focused not only on degradation rate, mechanism of photocatalytic process, but also identification of decomposition products and the pathways of DLX degradation. Due to application of the elaborated Z-scheme photocatalyst, the degradation rate constant was more than 2-3 times higher than that obtained for photolysis, but more important, the final compounds were mainly aliphatic products, formed by opening of aromatic rings. The chemical structure of the degradation products were determined with the use of HPLC and LC-MS. The toxicity of photoproducts with respect to water organisms was tested by means of Spirotox and Microtox assays. The Microtox test indicated that toxicity of the products after 6h of the solution irradiation in the presence of Z-scheme photocatalyst is about 4 times lower than that after photolysis.

Three birds with one stone: ZIF-8@g-C3N4 nanosheets simultaneously enhance barrier property, active protection and UV aging resistance of epoxy coatings

In order to address the challenge of the epoxy coating’s limited ability to mitigate electrochemical reactions following metal corrosion as well as its susceptibility to degradation and aging under ultraviolet irradiation, ZIF-8 (ZIF=Zeolitic Imidazolate Framework) was modified on the surface of Graphite-like carbon nitride (g-C3N4) nanosheets by in-situ loading method to construct ZIF-8@g-C3N4 (ZCN) smart nanoparticles which exhibited an acidic pH response with releasing Zn2+ cations and imidazole molecules to achieve an 87.2 % corrosion inhibition efficiency on carbon steel within 5 h. Modified by ZCN, epoxy coating (ZCN/EP) retained high barrier property even after a 40-day immersion in a 3.5 wt% NaCl solution. Meanwhile, ZCN responded to pH changes from localized corrosion, releasing inhibitors and forming zinc oxide/zinc hydroxide and Fe-Im chelate to further impede corrosion progression. Furthermore, combining the ability to absorb and reflect/scatter UV radiation, ZCN provided excellent UV resistance for ZCN/EP coatings to maintain exceptional anti-corrosion after 300 h of UV exposure, as well as good surface characteristics and thermal–mechanical properties. This work provides a novel concept for developing long-lasting coatings with multifunctionality.

Efficient cleavage of C-C bond in lignin adopting Z-scheme heterojunction photocatalyst by g-C3N4/CQDs/WO3

It is a practical approach to overcome the shortage of energy and environmental pollution simultaneously if obtaining useful products from biomass through chemical decomposition. Photocatalytic depolymerization of lignin to generate high value-added chemicals has received extensive attention for decades. The low yield of aromatic monomers is still one of the urgent problems to be solved. Selective breakage of Cα-Cβ bonds in lignin is of importance to improve the yield of aromatic monomers. Herein, Z-scheme heterojunction g-C3N4/CQDs/WO3 was constructed by combining graphite-like carbon nitride (g-C3N4), tungsten oxide (WO3) with carbon quantum dots (CQDs) to break the C-C bond selectively in β-O-4 model compounds. Both the efficiencies of substrate conversion and selectivity of C-C bond cleavage reached to 99 %. As a result, the total yield of benzaldehyde and benzoic acid attained to 83.92 %. Furthermore, the photocatalyst has satisfactory effect on depolymerization of four types of lignin, while the heterojunction can validly reduce the recombination rate of photogenerated carriers. Additionally, CQDs broadens the light absorption range and enhances the mobility of photogenerated carriers. Consequently, this study provides a feasible idea for highly selective cleavage of lignin C-C bonds through heterojunction engineering.

Synthesis of New Hybrid Materials of SiO2@Melamine-Cyanurate as Precursors for Graphite-Like Carbon Nitride

Synthesis of New Hybrid Materials of SiO2@Melamine-Cyanurate as Precursors for Graphite-Like Carbon Nitride

Construction of PEO@g-C3N4 supported ionic liquid membrane with interactive network structure for enhanced carbon capture efficiency

Polyethylene oxide (PEO) shows a high CO2-philic due to its dipolar-quadrupolar interaction with CO2 molecules. As a result, it is an excellent candidate for gas separation applications, yet it faces problems such as crystallization and low permeance. Herein, we show a versatile strategy to enhance gas permeation fluxes, which is mainly achieved by hindering the crystallization of PEO and the stacking of nanosheets. Specifically, graphite-like phase carbon nitride (g-C3N4) nanosheets are introduced and interaction networks (PGCN) are constructed by taking full advantage of the dipole-level quadrupole moment interactions between the ether-oxygen groups contained in PEO and CO2. In order to compensate the membrane surface defects for enhancing gas selectivity, we used the suspension coating method to create a PEO@g-C3N4 supported ionic liquid membrane (PGCN/ILX SILM) by coating IL on the surface of membrane. The results show that, when the IL concentration is 30 wt%, the PGCN/IL30 % membrane separates CO2/N2 with a CO2 permeance of 1396 GPU and an optimal selectivity of 58. While overcoming the “Trade-off” effect, it has demonstrated good thermal stability and long-term stable operation for 72 h. The development of this work will generate solutions for overcoming PEO crystallization and achieving efficient CO2 capture.

Electrochemical sensor based on Y-shaped DNA by “one-pot” method for mercury detection

A DNA electrochemical sensor based on Y-shaped DNA probes was successfully designed for Hg2+ detection. The sensor was modified with carbon self-doping graphite-like carbon nitride (C-g-C3N4) and electrodeposited gold nanoparticles (EAu) to enhance conductivity and enrich the binding sites for DNA. DNA probe (S1) binded on the modified electrode via –SH, forming a stable Y-shaped DNA double helix structure with probe S2 and probe S3 anchoring on gold nanoparticles (nanoAu) in the presence of Hg2+ solution. The Y-shaped DNA duplex, with its tight and nondeformable rigid structure, created well-defined stereoscopic reaction areas and efficiently captures Hg2+ due to its structural differences, thereby improving the signal response. Moreover, larger amounts of methyleneblue (MB) could be loaded to provide adequate electrochemical response signal. The proposed sensor possessing signal amplification ability displayed a linear relationship between the square wave voltammetry (SWV) peak currents. Under the optimal conditions, Hg2+ could be detected in the range from 5000.0 to 5.0 nM with a detection limit of 8.5 pM. The sensor was also tested with tap water, river and medical wastewater samples. It showed the good recovery and accuracy and represented a promising method for Hg2+ detection.

Bandgap modulations and promoted carrier separation in crystalline g-C3N4 thin films via chemical vapor deposition

The preparation of high-quality graphite-like phase carbon nitride (g-C3N4) films is challenging, which limits the potential optoelectronic and photocatalytic applications. Here, we report the growth of crystalline g-C3N4 films with thicknesses of approximately 100–200 nm on the indium tin oxide substrates by chemical vapor deposition. The films show high crystalline quality and uniformity as suggested by the appearance of interference fringes in the transmission spectra and the existence of exciton peak. The optimized growth conditions for high-quality g-C3N4 films deposition have been obtained through combined optical characterizations and detailed electronic structure analyses using x-ray spectroscopies. The as-grown g-C3N4 films exhibit a bandgap value of 3.05 eV as well as an enhanced fluorescence lifetime of ∼12.43 ns. By adding thiourea to the melamine precursors, N vacancies have been formed in the main heptazine structure, achieving the modulation of the bandgap and the promoted carrier separation. This work provides guidelines for understanding the property–structure relationships during g-C3N4 film deposition. The deposition of high crystallinity g-C3N4 films therein further extends the applications in the fields of optoelectronic and photocatalytic devices.

Fabricated layered g-C3N4 nanosheets for high efficiency photocatalytic degradation of atrazine：Insight into terminal-NHx in-situ activation of H2O2

It is well known that graphite-like carbon nitride (g-C3N4) is a good photocatalyst for in-situ the production of H2O2. However, how to activate H2O2 generating the strong oxidizing ·OH is the key factor to affect the degradation of pollutants. In this paper, the layered g-C3N4 nanosheets were prepared by using urea and H2O with different mass ratios and calcined in Muffle furnace by one-step synthesis method. The morphology, composition and structure of photocatalysts were analyzed, indicating that the as-prepared L-g-C3N4-7 had abundant edge regions in comparison with L-g-C3N4 made by solid urea. The photocatalytic performance of g-C3N4 nanosheets was investigated with atrazine (ATZ) as the target pollutant in water. The results revealed that the prepared L-g-C3N4-7 exhibited the best photocatalytic activity in visible light (λ ≥ 420 nm). The degradation of 1.0 mg/L ATZ reached over 96% after 3 hours and the photocatalytic degradation rate constant (k) was 6.8 times than that of L-g-C3N4 photocatalyst. In addition, under the same conditions, the H2O2 production of L-g-C3N4-7 was 4.5 times than that of L-g-C3N4 photocatalyst. Based on the capture experiments of free radicals, it was found that the contribution rate of ·OH in L-g-C3N4-7 photocatalytic increased to 17 % compared to 4 % of L-g-C3N4 photocatalyst during the degradation of ATZ. The ·OH quantitative experiment indicated that the L-g-C3N4-7 photocatalyst could obviously activate H2O2 to generate ·OH and the amount of ·OH was 2.5 times than that of the L-g-C3N4 photocatalyst. More importantly, a large amount of terminal-NHx (14.6 %) in L-g-C3N4-7 was measured by the XPS, FT-IR and zeta potential. The additive H2O2 adsorption experiment in the dark was used to confirm terminal-NHx sites of L-g-C3N4-7 photocatalyst, which was beneficial to adsorb and activate H2O2. The results illustrated that the L-g-C3N4-7 photocatalyst with rich edge regions and terminal-NHx had the characteristics of in-situ the activation of H2O2 to generate ·OH. The findings suggest that designing and developing efficient g-C3N4 photocatalysts pave a new avenue for activating in situ self-synthesizing H2O2 and the removal of atrazine in water.

Recent advances in ternary Z-scheme photocatalysis on graphitic carbon nitride based photocatalysts.

Due to its excellent photocatalytic performance over the last few years, graphitic-like carbon nitride (g-C3N4) has garnered considerable notice as a photocatalyst. Nevertheless, several limitations, including small surface area, the rates at which photo-generated electrons and holes recombine are swift, and the inefficient separation and transport of photoexcited carriers continue to impede its solar energy utilization. To overcome those limitations in single-component g-C3N4, constructing a heterogeneous photocatalytic system has emerged as an effective way. Among the various studies involving the incorporation of hetero composite materials to design heterojunctions, among the most promising approaches is to assemble a Z-scheme photocatalytic configuration. The Z-scheme configuration is essential because it facilitates efficient photocarrier separation and exhibits superior redox ability in separated electrons and holes. Moreover, ternary composites have demonstrated enhanced photocatalytic activities and reinforced photostability. Ternary Z-scheme heterostructures constructed with g-C3N4 possess all the above-mentioned merits and provide a pioneering strategy for implementing photocatalytic systems for environmental and energy sustainability. A summary of the latest technological advancements toward design and fabrication in ternary all-solid-state Z-scheme (ASSZ) and direct Z-scheme (DZ) photocatalysts built on g-C3N4 is presented in this review. Furthermore, the review also discusses the application of ternary Z-scheme photocatalytic architecture established on g-C3N4.

Smart epoxy coating: g-C3N4 nanosheets loaded MOFs for enhanced anti-corrosion and UV resistance

Large lateral size g-C3N4 nanosheets (Graphite-like carbon nitride) were successfully prepared by surface polymerization. NH2-MIL-101 (Amino-functionalized iron-based metal–organic framework) was then modified on the surface of g-C3N4 nanosheets (NH2-MIL-101@g-C3N4) by an in-situ loading method to construct a long-term smart coating with high barrier, activity inhibition, and anti-UV aging. This novel approach marks a significant advancement in the development of smart coatings for long-term corrosion protection. Evaluation of the active corrosion inhibition of NH2-MIL-101@g-C3N4 (MCN) nanoparticles showed that the corrosion inhibition efficiency of MCN nanoparticles on carbon steel reached 79.3 % after 5 h. The addition of MCN nanoparticles to the epoxy coatings (MCN/EP) endowed the coatings with the ability to actively inhibit corrosion. The release of Fe3+ cations and NH2-BDC (2-aminoterephthalic acid) organic ligands from MCN at defects formed a protective film, effectively preventing further corrosion. The MCN/EP coating maintained a high Log|Z|0.01 Hz value (Impedance modulus at a frequency of 0.01 Hz) during the immersion period with excellent barrier properties. Notably, MCN significantly improved the water resistance, water contact angle, tensile properties, and thermomechanical properties of epoxy coatings after ultraviolet (UV) radiation, highlighting a remarkable enhancement in the coating's performance. The anti-corrosion of MCN/EP coating was unaffected by UV radiation, extending service life of the smart coating, with Log|Z|0.01 Hz values two orders of magnitude higher than pure EP after 300 h of UV radiation. This work presented innovative coating design and preparation methods to improve the performance and functionality of anti-corrosion coatings, making significant attempts in the field.

Treatment of antibiotics in water by SO3H-modified Ti3C2 Mxene photocatalytic collaboration with g-C3N4

Due to inherent limitations such as high carrier recombination efficiency, limited active sites, and suboptimal utilization of visible light, graphite-like carbon nitride (g-C3N4) has constrained its widespread application in water treatment within photocatalytic systems. In addressing this issue, the present study employed acid etching and sonochemistry to fabricate a Ti3C2-SO3H/g-C3N4 (TiCSOHCN) composite photocatalyst for the removal of tetracycline hydrochloride (TC). The amalgamation of Ti3C2-SO3H (TiCSOH) with g-C3N4 engendered the establishment of a discernible Schottky barrier, facilitating an expedited electron transfer rate. Photocatalytic degradation experiments demonstrate that, compared to individual components, the TiCSOHCN composite photocatalyst exhibits significantly enhanced photocatalytic activity. The removal efficiency of TC reaches 75.42 % within 2 h, and even after five cycles of experimentation, the degradation efficiency remains close to 70 %, indicating excellent stability. The augmentation can be predominantly ascribed to the cooperative influence arising from the synergy between Ti3C2-SO3H and g-C3N4. The augmentation of visible light responsiveness in g-C3N4, achieved through its modification with TiCSOH, resulted in the mitigation of photoelectron-hole pair recombination, consequently leading to an amelioration in the photocatalytic efficacy of the TiCSOHCN composite catalyst. Intermediate species arising from the degradation of tetracycline were discerned utilizing LC-MS, and conjectures regarding plausible degradation pathways were postulated. Evaluations of the ecotoxicological impact of tetracycline and its intermediates indicated a progressive diminution in toxicity throughout the course of the photocatalytic degradation process. Furthermore, through free radical capture and EPR tests, it was confirmed that ·O2– and ·OH are the primary active species responsible for the photocatalytic degradation of TC, substantiating the proposed rational photocatalytic degradation mechanism. This research provides an innovative approach to developing high-performance and stable photocatalysts.

Sulfonic grafted graphitic-like carbon nitride for the improved photocatalytic production of benzaldehyde in water

This work reports the modification of graphitic carbon nitride (CN) through sulfonation (SCN) as an enhanced strategy for photocatalytic activity during the oxidation of benzyl alcohol to benzaldehyde. CN was prepared from melamine and functionalized with -SO3H groups using different doses of chlorosulfonic acid. The textural, structural, morphological, chemical, and optical properties of the prepared samples were characterized by diverse techniques. The increase in the doping dose produced, a decrease in surface area, a blue-shifted absorption edge under irradiation, and a decrease in the recombination charges. The -SO3H improved the kinetics of benzyl alcohol oxidation (BA) in aqueous solution and raised the selectivity to benzaldehyde (BD). An optimum dosage of precursor led to an SCN sample with the highest removal rate and selectivity. This optimized sample was selected for the study of the reactive oxidant species involved during the photocatalytic process, suggesting that the species with the highest contribution during BA oxidation was the superoxide radical, especially in terms of selectivity for the aldehyde formation. This work examples the modification of carbon nitride to enhance the production of an aldehyde with interest in the industry under a sustainable scheme that involves the transformation of light into chemical energy in aqueous solution.

Towards the photocatalytic production of cinnamaldehyde with phosphorous-tailored graphitic-like carbon nitride

Photocatalysis has emerged as an environmentally friendly technology to develop selective reactions such as the oxidation of alcohol to aldehydes. Graphitic carbon nitride (CN) is a metal-free polymeric structure easily photoactivated under radiation. This work focuses on the enhancement of the photocatalytic activity of bare CN by doping it with phosphorous (P-CN). Different doping levels of P (2–12 wt.) have been explored and the samples were fully characterized by XRD, FTIR, N2 physisorption, elemental analysis, XPS, DRS-UV–visible, and photoluminescence. A better activity and enhanced selectivity were observed in the P-CN samples if compared to the undoped CN in the oxidation of cinnamyl alcohol to cinnamaldehyde in aqueous solution. The presence of P was demonstrated to contribute to a better delocalization of photo-generated charges. Moreover, the reactivity and selectivity of the CN and P-CN samples were analyzed in water-acetonitrile mixtures, appreciating a better selectivity in the presence of acetonitrile to the detriment of the conversion of the cinnamyl alcohol. The photocatalytic oxidation mechanism over P-CN in aqueous media has been tentatively proposed based on the influence of the reactive oxidative species generated in the process by chemical scavenger tests. They suggested the contribution of superoxide radicals with more selectivity than the photo-generated holes, the second reactive species of importance in the overall oxidation scheme. The contribution of hydroxyl radicals was discharged since its presence was negligible in a probe test based on the formation of 2-hydroxy-terephthalic acid.

Implanting pyrazine ring into g-C3N4 for accelerating photocatalytic hydrogen evolution

It is of great significance to develop an efficient and stable photocatalyst for the photocatalytic decomposition of water to produce hydrogen. Within this paper, an effective and simple strategy was adopted to introduce pyrazine ring into graphite-like carbon nitride framework to realize efficient and stable hydrogen production process. After evaluation, the hydrogen production efficiency of the modified semiconductor material is 3.05 folds higher than the unmodified graphite-like phase carbon nitride, and an excellent stability performance was also achieved. It is proved that the light absorption ability of doped semiconductor composite nanomaterials was enhanced markedly by introducing 2-aminopyrazine into the carbon nitride structure. Meanwhile, the segregation efficiency of photo-induced carriers was obviously accelerated because the amino groups can work as hole trapping agents. Additionally, the introduced amino groups own Lewis alkalinity, which is in favour of the photoreduction. This work expands a new perspective of stable photocatalysts in the water split to produce hydrogen.

Analysis of degradation effect of carbon nitride nanomaterials in pollutant treatment

Abstract Photocatalytic technology is known as a green technology in solving energy problems and pollution problems, which can generate clean energy and degrade pollutants. In order to study the degradation performance of carbon nitride and its composites on air pollutants and water pollutants, this paper constructs TiO2/g-C3N4 composite photocatalysts by compositing graphite-like phase carbon nitride (g-C3N4) with titanium dioxide (TiO2) using titanium tetrachloride and melamine as raw materials in a water bath method. The physicochemical properties of the prepared complexes were analytically characterized by X-ray diffraction, UV-Vis diffuse reflectance, and X-ray photoelectron spectroscopy, and their degradation activities were examined and compared. The results of all the tests showed that the prepared 5 wt% TiO2/g-C3N4 nanocomposites performed better compared to other mass percentages of nanomaterials. The degradation of pollutants also resulted in better photocatalytic performance of the 5 wt% nanomaterials, with catalytic efficiencies of 54.2% and 99.5% for NO and methylene blue, respectively, at 30 min, and the good photocatalytic activity remained after five cycles.

Synergistic silver doping and N vacancy promoting photocatalytic performances of carbon nitride for pollutant oxidation and hydrogen production

Carbon nitride (C3N4) has attracted immense interest as a low-cost, non-toxic and naturally abundant raw material. However, graphite-like phase carbon nitride (g-C3N4) still suffers from poor visible light absorption, fast charge carrier recombination, slow electron mobility and relatively fewer surface-active sites. In this work, we synthesized silver-doped N vacancy-rich carbon nitride (AgCN) with convoluted ultra-thin lamellar layers from Ag precursors and melamine-cyanuric acid monomers using a self-assembly supramolecular strategy. AgCN exhibited excellent photocatalytic performance and stability. The introduction of N vacancies disrupted the off-domain π-bonds and weakened the conjugation effect of the triazine ring elements. The large specific surface area of the convoluted ultra-thin lamellar structure helps suppress the aggregation of active silver centers, and the Ag-N2C2 bond acts as a bridge for photoexcited charge transfer to promote the separation and transfer of photogenerated electron/hole pairs for surface redox reactions. As a result, AgCN exhibited excellent photocatalytic performance for photodegradation of rhodamine B (RhB) and hydrogen production (1.69 mmol g-1h−1), well outperforming the pristine CN. Density flooding theory (DFT) calculations revealed the improved conductivity and efficient separation of electron-hole pairs in AgCN at the excited state, generating superoxide radicals, singlet oxygen and holes.

Thermal stability improvement of azobenzene for the integration of photochemical and solar thermochemical energy conversion

Azobenzene is a typical photoisomerization material that is widely used in photochemical energy conversion. However, it's generally operated below 200 °C to avoid thermal decomposition. To improve the thermal stability of azobenzene for higher temperature applications, this paper discussed an option that grafting azobenzene onto graphite-like carbon nitride sheets. The synthesis was evaluated based on the performance of micro morphology and structure, thermal stability, and photochemical energy conversion. Furthermore, the photochemical conversion performance was analyzed with diverse irradiation intensities. The results demonstrate that the synthesis has a strong thermal stability below 530 °C. In this study, the most favorable excitation wavelength for photochemical conversion was 445 nm with an irradiation intensity of 40 mW/cm2.

A NEW STRATEGY FOR THE SYNTHESIS OF HIGHLY ACTIVE CATALYSTS BASED ON <i>g-</i>C<sub>3</sub>N<sub>4</sub> FOR THE PHOTOCATALYTIC PRODUCTION OF HYDROGEN UNDER VISIBLE LIGHT

In this work, materials based on graphite-like carbon nitride were synthesized by thermal treatment of a mixture of melamine and urea and the effect of synthesis conditions on the photocatalytic activity of the samples was studied. As a cocatalyst, platinum (1 wt. %) was deposited on the surface of the synthesized g‑C3N4 samples. The photocatalysts were characterized by X-ray phase analysis, diffuse reflectance UV-vis spectro-scopy in the UV and visible range, and low-temperature nitrogen adsorption. Photocatalytic activity was determined in the reaction of hydrogen evolution from an aqueous solution of triethanolamine (10 vol. %) under visible light irradiation (λ = 425 nm). The optimal conditions for the synthesis of the photocatalyst 1% Pt/g-C3N4, obtained by calcination of a mixture of melamine and urea (1 : 3), were found, using which the rate of H2 evolution was 5.0 mmol g–1 h–1 with an apparent quantum efficiency of 2.5%. The developed synthetic approach makes it possible to obtain highly active catalysts due to the formation of an intermediate supramolecular melamine-cyanuric acid complex during the synthesis, which, upon further heating, turns into g-C3N4, which is characterized by a high specific surface area exceeding 100 m2 g–1.