Phenyl-modified carbon nitride nanosheets: Enhanced photocatalytic activity via sonication-assisted exfoliation

Alkali-assisted fabrication of holey carbon nitride nanosheet with tunable conjugated system for efficient visible-light-driven water splitting

In this study, the porous ultrathin graphitic carbon nitride (CN) nanosheets with rich C and nitrogen defects were prepared by one-step calcining the mixture of melamine and glucose (Glu) in air atmosphere (Glu-CN). Introducing simultaneously rich C atoms and nitrogen defects into CN structures continuously modulates the bandgaps from 2.67 to 1.81 eV of CN photocatalysts. Due to large surface area, more active sites, remarkably longer lifetime of charge carriers and adjustable band gap structure, the prepared ultrathin porous CN nanosheets show the enhanced photocatalytic performance for the degradation of methyl orange (MO) under visible light. The degradation efficiency of optimal CN nanosheet photocatalyst for MO is 5.75 times that of bulk CN. This work provides a facile and universal relevance approach to engineer the band structures of CN by introduction of rich C and porous morphology for high-performance photocatalytic, which can provide informative principles for the design of efficient photocatalysis systems for solar energy conversion.

Novel carbon nitride (CN) nanosheets are for the first time fabricated by facial supramolecular approach using cyanuric acid, melamine, and 2,4‐diamino‐6‐methyl‐1,3,5‐triazine as starting materials. This is also the first report where the third monomer is used in such synthetic route. With the unique structural advantages for efficient separation of photoinduced charge–hole pairs, light absorption, and the richly available restive sites, the as‐synthesized porous CN nanosheets exhibit a superior photocatalytic hydrogen evolution activity whether they are under simulated solar light or under visible light (λ > 420 nm) irradiation. The hydrogen evolution rate can reach 11 946.1 µmol h−1 g−1 under visible light irradiation, to the best of our knowledge, the highest of all the metal‐free CN semiconductor photocatalysts. Also, the synthetic holey CN nanosheets exhibit excellent photocatalytic oxidation performance of high concentration nitric oxide (NO, ≈400 ppm) and outstanding photocatalytic degradation of rhodamine B under visible light. The supramolecular synthesis of multifunctional CN nanosheets using suitable monomers as raw materials may provide a possible pathway for alleviating energy issues and environmental pollution problems.

Synthesis of nitrogen vacancy-riched ultrathin polymeric carbon nitride nanosheets via ethanol-ethylene glycol ultrasonic exfoliation and photocatalytic hydrogen evolution activity

In this paper, we reported a new and environment-friendly strategy to exfoliate graphitic carbon nitride (CN) in hot water to obtain ultrathin CN nanosheets (CNNS). By thermal treating, water molecules were intercalated into the interlayer space of bulky CN and further hydrolyzed the bridge-linked N groups between tri-s-triazine units, thereby cutting the CN layers into CNNS. Due to the negative charges on surface (Zeta potential was −13 mV at pH 7), the CNNS colloids were extremely stable. The physicochemical characterization indicated that the as-prepared CNNS had a typical 2D morphology with a ~1.2 nm thickness and numerous –OH groups on surface. Moreover, the high charge separation and transport ability were achieved in CNNS because of the retaining of conjugated CN system. Compared to the bulk CN, the as-prepared ultrathin CNNS exhibited an enhanced photocatalytic performance (four times higher than that of the bulk CN) for degradation of organic dye under visible light irradiation. Additionally, the superior reusability and the excellent generality of CNNS for decomposing other pollutants were also demonstrated. Finally, we proposed a possible mechanism of CNNS based on the examined band structure and the main active species determined by quenching of various active species.

Graphitic carbon nitride nanosheet (CNS) represents an attractive candidate for solar fuel production. However, the abundant defects in CNS lead to serious charge recombination and limit the photocatalytic performance. Herein, the synthesis of a CNS-covalent organic framework (CNS-COF) nanosheet composite is presented for the first time. CNS with significantly reduced defects is first obtained by rationally tuning the thermal exfoliation conditions of bulk carbon nitride. Subsequent modification of the CNS with trace COF nanosheet through chemical imine bonding can not only passivate the surface termination of carbon nitride in the boundary region, but also establish strong electronic coupling between these two components. As a consequence, enhanced charge separation and photocatalytic activity are realized on the resulting CNS-COF nanosheet composite. Under optimum conditions, hydrogen is evolved at a rate of 46.4 mmol g-1 h-1 . This corresponds to an apparent quantum efficiency of 31.8% at 425 nm, which is among the best values ever reported for carbon nitride-based materials.

BIF-20, a zeolite-like porous boron imidazolate framework with high density of exposed B-H bonding, is combined with graphitic carbon nitride (g-C3N4) nanosheets via a facile electrostatic self-assembly approach under room temperature, forming an elegant composite BIF-20@g-C3N4 nanosheet. The as-constructed composite preferably captures CO2 and further photoreduces CO2 in high efficiency. The photogenerated excitations from the carbon nitride nanosheet can directionally migrate to B-H bonding, which effectively suppresses electron-hole pair recombination and thus greatly improves the photocatalytic ability. Compared to the g-C3N4 nanosheet, the BIF-20@g-C3N4 nanosheet composite displayed a much-enhanced photocatalytic CO2 reduction activity, which is equal to 9.7-fold enhancements in the CH4 evolution rate (15.524 μmol g-1 h-1) and 9.85-fold improvements in CO generation rate (53.869 μmol g-1 h-1). Density functional theory simulations further prove that the presence of B-H bonding in the composite is favorable for CO2 adhesion and activation in the reaction process. Thus, we believe that the implantation of functional active sites into the porous matrix provides important insights for preparation of a highly efficient photocatalyst.

Efficient singlet oxygen generation by excitonic energy transfer on ultrathin g-C3N4 for selective photocatalytic oxidation of methyl-phenyl-sulfide with O2

Carbon nitride (CN) nanosheets with a thickness of around 3 nm were prepared by pyrolysis of urea. Well-dispersed Pt nanoparticles of about 3 nm were pre-loaded on CN nanosheets as the co-catalyst by chemical reduction in ethylene glycol. The Pt/CN sample showed a H2 evolution rate of 45.1 μmol h−1 from an aqueous solution of triethanolamine (TEOA) under visible light irradiation (λ > 420 nm). By simply adding a low-cost dye Erythrosin B (ErB) in the photoreaction suspension, a remarkably enhanced H2 evolution rate of 652.5 μmol h−1 was observed. Efficient electron transfer from excited ErB to the conduction band of CN is expected due to the energy difference between the LUMO level of excited ErB (−3.59 eV vs. vacuum level) and the conduction band potential of CN (−3.71 eV vs. vacuum level). A dye sensitization mechanism between ErB and CN is proposed. Upon irradiation with light of long wavelength (λ > 550 nm), the Pt/CN–ErB photocatalyst system still exhibited a high H2 evolution rate of 162.5 μmol h−1. The highest quantum efficiency of 33.4% was obtained at 460 nm. Moreover, the Pt/CN photocatalyst could be easily recycled by simple filtration and 90% of the activity was still kept after five consecutive runs.

Carbon nitride (CN)-based heterojunction photocatalysts hold promise for efficient carbon dioxide (CO2) reduction. However, suboptimal production yields and limited selectivity in CO2 conversion pose significant barriers to achieving efficient CO2 conversion. Here, we present the construction of a p-n heterojunction between ultrasmall Te NPs and CN nanosheet using a novel tandem hydrothermal-calcination synthesis strategy. Through ammonia-assisted calcination, ultrasmall Te NPs are grown in-situ on the CN nanosheets’ surface, resulting in the generation of a robust p-n heterojunction. The synthesized heterojunction exhibits increased specific surface area, reinforced visible light absorption, intensive CO2 adsorption capacity, and efficient charge transfer. The optimum Te/CN-NH3 demonstrates superior photocatalytic CO2 reduction activity and durability, with nearly 100 ​% selectivity for CO and a yield as high as 92.0 ​μmol ​g−1 ​h−1, a fourfold increase compared to pure CN. Experimental and theoretical calculations unravel that the strong built-in electric field of the Te/CN-NH3 p-n heterojunction accelerates the migration of photogenerated electrons from Te NPs to the N site on CN nanosheets, thereby promoting CO2 reduction. This study provides a promising material design approach for the construction of high-performance p-n heterojunction photocatalysts.

In this research, bulk graphitic carbon nitride (g-C3 N4 ) is exfoliated and transferred to the carbon nitride nanosheets (CNNSs), which are then coupled with MIL-88B(Fe) to form the hybrid. From the results of the powder X-ray diffraction, scanning electronic microscopy and thermogravimetric analysis, it is found that the doping of CNNSs on the surface of MIL-88(Fe) could maintain the basic structure of MIL-88B(Fe), and the smaller dimension of CNNSs might influence the crystallization process of metal-organic frameworks (MOFs) compared to bulk g-C3 N4 . Besides, the effects of the CNNSs incorporation on photocatalysis are also investigated. Through the photoluminescence spectra, electrochemical measurements, and photocatalytic experiments, the hybrid containing 6% CNNSs is certified to possess the highest catalytic activity to degrade methylene blue and reduce Cr(VI) under visible light. The improvement of the photocatalytic performance can be attributed to the matched energy level which favors the formation of the heterojunctions. Besides, it promotes the charge migration such that the contact between MOFs and CNNSs is more intimate, which can be inferred from the electronic microscopy images. Finally, a possible photocatalytic mechanism is put forward by the relative calculation and the employment of the scavengers to trap the active species.

A facile and scalable route for synthesizing ultrathin carbon nitride nanosheets with efficient solar hydrogen evolution

Synergistic effect of light in piezocatalytic activation of peroxymonosulfate using graphtic carbon nitride nanosheets for degradation of organic pollutants

Facile synthesis of Ag3PO4/g-C3N4 composites in various solvent systems with tuned morphologies and their efficient photocatalytic activity for multi-dye degradation

Evaluation of interaction mechanism between 2-dimensional (2D) nanomaterials and cell membranes is a critical issue in providing guidelines for biomedical applications. Recent progress in computer-aided molecular design tools, especially molecular dynamics (MD) simulation, afford a cost-effective approach to achieving this goal. In this work, based on this hypothesis, by utilizing theoretical methods including MD simulation and free energy calculations, a process is evaluated in which the Doxorubicin (DOX)-loaded onto carbon nitride (CN) nanosheet faced with bilayer membrane. It should be mentioned that to achieve an efficient CN-based drug delivery system (DDS), in the first place, the intermolecular interaction between the carrier and DOX is investigated. The obtained results show that the DOX prefers a parallel orientation with respect to the CN surface via the formation of π–π stacking and H-bond interactions. Furthermore, the adsorption energy value between the drug and the carrier is evaluated at about − 312 kJ/mol. Moreover, the investigation of the interaction between the CN-DOX complex and the membrane reveals that due to the presence of polar heads in the lipid bilayer, the contribution of electrostatic energy is higher than the van der Waals energy. The global minimum in free energy surface of the DDS is located between the head groups of the cell membrane. Overall, it can be concluded that the CN nanosheet is a suitable candidate for transfer and stabilize DOX on the membrane.