Graphite Phase Carbon Nitride Research Articles

Nickel-decorated graphite phase carbon nitride photocatalysts coupled with carbazole-based calixarene dyes for high-efficiency visible light-driven hydrogen evolution

The development of artificial devices that mimic the highly efficient and sophisticated photosystems found in nature is a subject worthy of in-depth study. Two calixarene D-π-A dyes, C4-CZSTP and C4-CZBTP, containing an N-methylcarbazole group as a secondary auxiliary electron donor, are synthesized on the basis of our previously reported calixarene dye C4-BTP. These dyes are then cooperated with Ni-deposited g-C3N4 to prepare ternary photocatalysts, denoted as C4-CZSTP/Ni/g-C3N4, C4-CZBTP/Ni/g-C3N4 and C4-BTP/Ni/g-C3N4, and their photocatalytic performances are evaluated under visible light irradiation. The optimized 4.0 wt% C4-CZSTP/Ni/g-C3N4 sample gives a remarkable H2 evolution rate of 5552 μmol g−1 h−1, representing one of the highest records among the reported analogous systems based on g-C3N4. And after an extended test of 49 h, a total H2 yield of 63.57 mmol g−1 is obtained, corresponding to a turnover number (TON) based on C4-CZSTP moles (TONC4-CZSTP) of 3180. This performance can be attributed to the enhanced light-harvesting and photoelectron conversion of the as-prepared calixarene dyes, the adjusted energy levels and the effective cooperation of the three components. The optimal performance of C4-CZSTP/Ni/g-C3N4 among the three dye-sensitized systems is due to its higher lowest unoccupied molecular orbital (LUMO) value, i.e. stronger electronic driving force from the excited dye to g-C3N4. This study provides an interesting example for the design and preparation of a low-cost, high-efficiency and noble metal-free photocatalytic system for solar fuel production.

Vesicular BiVO4 nanostructures modified by g-C3N4 quantum dots for enhanced photocatalytic activity

Photocatalysis technology has been an available method to alleviate the improper discharge of dye wastewater by employing light energy to degrade the dye pollutants. Here, the vesicular BiVO4 hollow structures were modified by graphite phase carbon nitride quantum dots (CNQDs) to construct the BiVO4-based photocatalyst (BiVO4/CNQDs) for the enhanced removal of dye molecules. The CNQDs with a diameter of 2–5 nm evenly decorate on BiVO4 vesicles to construct the close interface of the BiVO4/CNQDs heterojunctions. Compared with vesicular BiVO4, the enhanced visible-light decomposition of methyl orange (MO) comes down to the coordination of different components, the C and/or N doping and hollow structure. This is helpful to increase surface area of bulk BiVO4, broaden light response, narrow band gap and obstruct charge combination. Especially, the up-conversion luminescence of the CNQDs can induce BiVO4 to generate more photo-excited electrons to participate in the MO photo-degradation reaction. The BiVO4/CNQDs heterojunctions with the unique hollow structure and excellent photocatalytic activity display the promising utilization in wastewater treatment.

Metal-free catalysts with local fluorination regulation for peroxymonosulfate activation: Nearly 100 % singlet oxygen production for selective degradation of aqueous organic pollutants

Generating singlet oxygen (1O2) via activating peroxymonosulfate (PMS) is crucial for the selective removal of organic pollutants in aquatic environments. However, achieving efficient and selective conversion of PMS into 1O2 without consuming energy or metals remains a significant challenge. In this study, graphite phase carbon nitride (g-C3N4) was locally fluorinated via a simple polymerization method. The local fluorinated g-C3N4 (FCN) was used as a metal-free catalyst to activate PMS, enabling highly efficient degradation of 4-chlorophenol (100 %) and detoxification. The FCN/PMS system demonstrates exceptional selectivity for electron-rich pollutants, functions effectively across a broad pH range (2–10), and exhibits remarkable interference resistances to background scavenging ions and natural organic compounds. Furthermore, quenching experiments, probe tests, electron paramagnetic spin resonance measurements, electrochemical characterizations, and theoretical calculations demonstrated that 1O2 was the only reactive species in the catalytic process. Local fluorination regulated the electronic structure of g-C3N4, juxtaposing electron-rich fluorine with electron-deficient carbon dual active sites. This modification alters the electron transfer direction between PMS and g-C3N4, allowing for nearly 100 % selective generation of 1O2via dual electron transfer channels without the need for energy or metals. This study provides a new strategy for designing metal-free heterogeneous catalysts to selectively generate 1O2 in a green way and can facilitate the wider applications of advanced oxidation processes for water purification.

Effective degradation of phenol by activating PMS with bimetallic Mo and Ni Co-doped g C3N4 composite catalyst: A Fenton-like degradation process promoted by non-free radical 1O2

The application of bimetal supported graphite phase carbon nitride in activated peroxymonosulfate (PMS) process has become a research hotspot in recent years. In this study, 8-g C3N4/Mo/Ni composite catalyst material was successfully prepared by doping Mo and Ni in graphite phase carbon nitride. The bimetallic active sites were formed in the catalyst, and PMS was activated by the metal valence Mo6+/Mo4+ and Ni2+/Ni(0) through redox double cycle to effectively degrade phenol. When pH was neutral, the degradation rate of 20 mg/L phenol solution with 8-g C3N4/Mo/Ni (0.35 g/L) and PMS (0.6 mM) could reach 95% within 20 min. The degradation rate of 8-g C3N4/Mo/Ni/PMS catalytic system could reach more than 90% within 20min under the condition of pH range of 3–11 and different anions. Meanwhile, the degradation effects of RhB, MB and OFX on different pollutants within 30min were 99%, 100% and 82%, respectively. Electron spin resonance and quenching experiments showed that in 8-g C3N4/Mo/Ni/PMS system, the degradation mechanism was mainly non-free radicals, and the main active species in the degradation process was 1O2. This study provides a new idea for the study of bimetal supported graphite phase carbon nitride activation of PMS and the theoretical study of degradation mechanism.

Analysis of Photocatalytic Properties of NS-CQDs/g-C3N4 Composites.

N- and S-doped CQDs were prepared using L-cysteine as a precursor. Different NS-CQDs/g-C3N4 composite photocatalysts were formed by modifying graphite-phase carbon nitride with different contents of NS-CQDs using a hydrothermal method. The morphology, constituent elements and functional groups of the composite photocatalysts were analyzed by SEM, EDS, TEM, Mapping, XRD and FT-IR as a proof of its successful preparation. Meanwhile, it was characterized by PL, UV-Vis DRS and electrochemical impedance, which proved that the CQDs could be used as an electronic memory in the composite system to accelerate the electron transfer induced by the photo-excitation of g-C3N4 and effectively inhibit the recombination of e--h+ improvement of the photocatalytic activity of g-C3N4. The stability of the composite photocatalysts under different conditions and the photodegradation activity of Rh B under visible light were investigated. It was found that the photocatalytic degradation efficiency of rhodamine B by NS-CQDS-modified g-C3N4 was significantly higher than that of pure g-C3N4, which could reach 90.82%, and its degradation rate was 3.5 times higher than that of pure g-C3N4. It was demonstrated by free radical trapping experiments that ·OH and ·O2- were the main active species in the photocatalytic degradation process, in which ·O2- played a guiding role.

Comparison of Modification Methods of Photocatalyst G-C3N4 in Hydrogen Production Performance

Non-metallic polymer semiconductor graphite phase carbon nitride (g-C3N4) is a low-cost, environmentally friendly raw material with suitable bandgap width and stable chemical properties. However, there are still problems such as lower surface area, higher recombination rate of photo-excited charge carriers, and lower utilization rate of visible light. This paper introduces the structure, physicochemical properties, preparation methods, and modification ideas of graphite phase carbon nitride, focusing on several popular modification achievements in recent years, as well as a horizontal comparison of their respective production methods, mechanisms, and hydrogen production efficiency. Finally, the challenges and prospects in the modification of carbon nitride are discussed.

Accelerated bone defect repairment by carbon nitride photoelectric conversion material in core–shell nanofibrous depended on neurogenesis

Highly efficient bone repair materials are essential for the clinical treatment of large bone defects. This study aimed to develop nanofibrous scaffolds for bone defect repairment. Here, we reported that insulin like growth factor (IGF) adsorbed into phosphorus doped graphite phase carbon nitride (C3N4(P)) as core, and nerve growth factor (NGF) adsorbed into silk fibroin (SF) as shell to prepare nanofibrous scaffolds (IGF@C3N4(P)/NGF@SF) by coaxial electrospining for accelerating bone formation. Additionally, C3N4(P) was employed as a photoelectric conversion material capable of achieving the mutual conversion of light and electricity. Remarkably, we found that red light + IGF@C3N4(P)/NGF@SF scaffold may enhance osteogenesis in bone mesenchymal stem cells (BMSCs) by activating the extracellular regulated protein kinases1/2 (Erk1/2), which subsequently activated runt-related transcription factor 2 (Runx2) and the mammalian target of rapamycin (mTOR) pathway. Consequently, the mRNA expression levels of downstream osteogenic related genes were increased. Furthermore, we observed that red light + IGF@C3N4(P)/NGF@SF scaffold promoted BMSCs induced neural differentiation cells differentiated into neuron and upregulated the mRNA expression levels of neuron specific related genes. Interestingly, we also demonstrated the formation of new neurons in the Haversian canal within the cranial defect area in mice, indicating that red light + IGF@C3N4(P)/NGF@SF scaffold promoted osteogenesis with neurogenesis. Moreover, our RNA sequencing results supported the activation of neurogenesis along with osteogenesis. Based on these novel findings, we conclude that red light + IGF@C3N4(P)/NGF@SF scaffold exhibits great potential as a prospective biomaterial for promoting bone defect repairment with neurogenesis, and the utilization of red light is crucial in facilitating this process.

Preparation of g-C3N5 composites for butyl xanthate photocatalytic degradation

The nitrogen-rich graphite-phase carbon nitride (g-C3N5) supported TiO2 photocatalyst (Ti-CN) was prepared using TiO2 and 3-amino 1, 2, 4-triazole as raw materials for butyl xanthate residual (SBX) removal from mineral processing wastewater. The crystal, morphology, specific surface area and optical properties of the Ti-CN were characterized by XRD, TEM, UV–vis DRS, BET and PL. These results showed that TiO2 particles were uniformly dispersed on g-C3N5 nanosheets, and the heterojunction was formed. The formation of heterojunction improved its response to visible light, and promoted the separation of photoelectron-hole, contributing to improving its photocatalytic activity. The influence of catalyst dosage, initial SBX concentration and pH value of the SBX solution on SBX photocatalytic degradation removal was investigated. The Box-Behnken design of the response surface was used to optimize the process conditions to obtain the optimal experiment conditions with the pH of 7.04, catalyst dosage of 50.2 mg and SBX concentration of 56.6 mg/L. The SBX photocatalytic degradation removal of Ti-CN is 98.15 %, which is close to the predicted value of 97.75 % at the optimal experiment conditions. Meanwhile, the SBX degradation removal of Ti-CN still had 90.21 % after five cycles, indicating that Ti-CN has good stability. These results indicate that Ti-CN can be used as the promising photocatalyst for SBX from mineral processing wastewater.

Porous organic semiconductor/PET composite fibre for the synergistic removal of hexavalent chromium and organic pollutants under sunlight

ABSTRACT In this study, the porous graphite phase carbon nitride photocatalyst (P-g-C3N4) is prepared by the CaCO3 template method, and then P-g-C3N4/T-polyethylene terephthalate (T-PET) catalytic fibre is prepared by the padding method. P-g-C3N4 can provide more active sites than g-C3N4 as proved by the Brunauer–Emmett–Teller and the UV–Visible diffuse reflectance test. P-g-C3N4 powder catalyst successfully supports PET fibre as proved by scanning electron microscope, Fourier infrared spectroscopy and X-ray diffraction spectroscopy. The photocatalytic performance of P-g-C3N4/T-PET catalytic fibre is tested by constructing a single hexavalent chromium or hexavalent chromium/organic pollutant binary pollution system. The potential application value of P-g-C3N4/T-PET catalytic fibre is further explored by simulating the complex actual water environment. After five recycles, P-g-C3N4/T-PET catalytic fibre shows good catalytic performance. The mechanism of P-g-C3N4/PET photocatalytic degradation of organic pollutants is proposed through the capture agent experiment and electron paramagnetic resonance spectroscopy. Among them, •O2 − is the most important active species of P-g-C3N4 catalytic fibre, which is used for the oxidation of organic pollutants. At the same time, photoelectrons generated by the catalytic fibre are used to reduce hexavalent chromium. The efficiency of P-g-C3N4 to remove pollutants is improved by using PET fibre as a carrier, which not only solves the problem of difficult recovery of powder catalysts but also provides more active sites.

Photocatalytic activity and mechanism of PCN@GO/AgNPs heterojunction in Rhodamine B degradation

An essential factor affecting the photocatalytic efficiency of a catalyst is the efficient separation of photogenerated electrons and holes. In the present study, a novel heterojunction material, PCN@GO/AgNPs, was synthesized with the aim of improving the photocatalytic performance. This achievement was accomplished through the establishment of a heterojunction between graphitic phase carbon nitride (PCN) and nano silver (AgNO3). The PCN was prepared from melamine powder calcined at high temperature under nitrogen environment, and was modified by graphene oxide (GO) to form heterojunction with silver nanoparticles, which resulted in a significant improvement in the photocatalytic efficiency of the catalyst. Under ultraviolet（UV）excitation, the catalytic rate constant of PCN@GO/AgNPs heterojunction on RhB dye can reach 10.594 × 10−2 min−1. This research represents a promising strategy to increase the surface area of PCN photocatalysts through simply doping noble metal and thus improving photocatalytic performance, which contributes to understand the reaction mechanism of photocatalytic effect.

A ratiometric fluorescent probe for hypoxanthine detection in aquatic products based on the enzyme mimics and fluorescence of cobalt-doped carbon nitride

A ratiometric fluorescent probe for hypoxanthine (Hx) detection was established based on the mimic enzyme and fluorescence characteristics of cobalt-doped graphite-phase carbon nitride (Co doped g-C3N4). In addition to emitting strong fluorescence, the peroxidase activity of Co doped g-C3N4 can catalyze the reaction of O-phenylenediamine and H2O2 to produce diallyl phthalate which can emit yellow fluorescence at 570 nm. Through the decomposition of Hx by xanthine oxidase, Hx can be indirectly detected by the generating hydrogen peroxide based on the measurement of fluorescent ratio I (F570/F370). The linear range was 1.70–272.2 mg/kg (R2 = 0.997), and the detection limit was 1.52 mg/kg (3σ/K, n = 9). The established method was applied to Hx detection in bass, grass carp, and shrimp, and the data were verified by HPLC. The result shows that the established probe is sensitive, accurate, and reliable, and can be used for Hx detection in aquatic products.

Pretreatment strategies of precursors for efficient photocatalytic hydrogen production of graphitic phase carbon nitride

The most sustainable preparation method for nanostructured materials must be urgently determined. In particular, the influence of different precursor pretreatment strategies on the structure and photocatalytic performance of highly attractive Graphitic carbon nitride photocatalyst is necessary to determine the most effective precursor pretreatment strategy. In this paper, three different precursor pretreatment methods were used to prepare g-C3N4 materials, so namely direct mixing (CN-C), freeze-drying, hydrothermal (CN-H) with thermal condensation polymerization two-step method processed urea, melamine and NH4Cl precursor mixtures. The results showed that NH4Cl, as a template, would not destroy the integrity of the tristriazine structural units in the product, and the CN-H sample had a lamellar structure, and the specific surface area and pore volume of the sample increased, which could provide more active reaction sites for photocatalytic H2 production, had the highest and most stable H2 evolution rate, up to 118.4 μmol g−1, about 1.7 times CN-C’s. This strategy provides a new idea for the design of g-C3N4 photocatalyst.

The relationship between the fabrication and characteristics of nitrogen-doped graphene

Since the 21st century, with the popularization of computers and mobile phones to the upgrading of various kinds of electronic products, human needs are also changing, among which the flexible touch screen has received wide attention. To achieve a wide application of flexible touch screens, this paper needs to make more materials innovations, and graphene’s unique and excellent performance has attracted wide attention. Among them, the metal doping, non-metallic doping, metallic and non-metallic co-doping of graphite phase carbon nitride has broad development prospects, widely used, or may be widely used in the production and production of flexible touch screen. This paper briefly analyzes and compares three nitrogen-containing graphene materials’ properties and preparation methods (metal doping, non-metal doping, metal, and non-metal co-doping) in 2D nanomaterials, and discusses the possible applications in the field of flexible touch screens. Urea-reduced GO graphene, Fe-P co-doped graphite phase nitride carbon and potassium ion-doped graphite phase nitride carbon all have easy raw materials, simple production mode, electrical, and excellent optical properties; meanwhile, different doping methods and dosage change the performance of graphene in different directions. Therefore, nitrogen-containing graphene materials have a lot for development in the part of flexible touch screens.

The promoted photocatalytic performance of in-situ surface alkalinization of g-C3N4 for methylene blue and Cr(VI) in dye wastewater

In this paper, a series of surface-alkalinized graphitic phase carbon nitride (g-C3N4) were synthesized via a one-step strategy employing dicyandiamide as the precursor. The effects of single salts (KCl, NH4Cl) and complex salts (KCl with NH4Cl) on the morphological structure, compositional composition, optical properties, and photocatalytic performance of alkalized CN samples were investigated. The IR and XPS analyses revealed that new structural units, C≡N and (N)2C-OH, were formed in the CN structure, indicating that the surface alkalinization of g-C3N4 had been successful. After in-situ surface alkalinization, the energy band structure of CN was optimized, the light absorption range was widened, and the photocatalytic activity was enhanced. Among them, the compound salt alkalinized sample (CNK2.0) at twice the amount of KCl as dicyandiamide showed the most excellent photocatalytic degradation performance. Its degradation efficiency of methylene blue within 60 min could reach 83.39 %, which was 2.05 times higher than that of pure g-C3N4. With a 47.1 % reduction of Cr(VI) at 60 min, the CNK1.5 sample demonstrated the prime photocatalytic activity, which was 34.2 % higher than that of pure g-C3N4. The surface hydroxylation and the optimization of the energy band structure are the main reasons for the enhanced photocatalytic activity of carbon nitride after complex salt alkalinization.

Peptide-antifouling interface for monitoring β-amyloid based on electrochemiluminescence resonance energy transfer

In this study, a novel antifouling electrochemiluminescence (ECL) analytical platform has been developed for the highly sensitive quantification of β-amyloid (Aβ) peptides based on the ECL resonance energy transfer (ECL-RET) mechanism. Specifically, glassy carbon electrodes (GCE) were initially coated with graphite-phase carbon nitride (g-C3N4) nanosheets, followed by the electropolymerization of polyaniline (PANI) onto the electrode surface. Subsequently, a promising peptide motif candidate (COOH-CPPPPDKDKDKDKKLVFF) was immobilized onto the PANI-modified electrode, functioning as a critical component for both antifouling and specific recognition of full-length Aβ peptides. Furthermore, this peptide motif demonstrated inhibitory effects on Aβ aggregation and dissociation. Upon immobilization of the peptide motif, Aβ aptamer-CdS QDs were bound to the electrode surface through peptide-specific interactions with Aβ, thereby facilitating the highly sensitive ECL detection of Aβ. Under the optimal conditions, the proposed biosensor exhibited an Aβ detection range from 0.1 pM to 100 nM with a detection limit of 16.1 fM. As such, this innovative platform offers a straightforward approach to antifouling, quantification, and monitoring of Aβ concentrations in the blood samples.

Detection of cadmium (II) ion in water by a novel electrochemical sensor based on modification of graphite carbon nitride and polyaniline composite

A novel electrochemical sensor was constructed based on modification of polyaniline (PANI) and graphitic-phase carbon nitride (g-C3N4) composites. Detection of Cd(II) ions in the aqueous environment using differential pulsed anodic stripping voltammetry (DPASV) technique. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), contact angle (CA), and Tafel curve analyses were used to characterize the physical and electrochemical properties of electrode. We prepared a new PANI@g-C3N4 composite material by combining the two substances based on their respective advantages. The composite material was applied to electrode detection for the first time, which significantly enhanced the transfer of free electrons on the surface of the electrode, improved the sensitivity of the electrode, increased the adsorption capacity of Cd ions, and significantly improved the detection effect of the electrode. Parameters such as the amount of PANI@g-C3N4 modification, deposition potential, deposition time and solution pH were optimized to determine the best conditions for the detection of Cd(II) ions. Under optimal conditions, our sensor achieves a best signal at −0.78 V (vs. Ag/Agcl electrode), and exhibits a wide linear concentration range of 0.1–140 μg/L with a low detection limit of 0.05 μg/L. The sensor was successful in implementing the identification of real water samples with recoveries ranging from 91 % to 106 %. The relative standard deviation (RSD) is less than 4.31 %. Besides, the sensor has outstanding anti-interference, repeatability and steadiness. The successful application of this sensor provides a new idea for efficient detection of Cd(II) ions in aquatic environments.

Preparation of RE/g-C3N4 Photocatalysts by Thermal Polycondensation Method and Its Properties

Graphite phase carbon nitride photocatalysts (RE/g-C3N4) doped with different rare earths (RE=La, Ce, Sm, Nd, Eu) were prepared by thermal polycondensation method using rare earth metal nitrate and melamine as raw materials. The photocatalytic performance of RE/g-C3N4 was studied through using photo-degradation reaction of methylene blue (MB) as the evaluation model. The effects of calcination temperature, rare earth elements type and doping ratio on the photocatalytic performance of g-C3N4 were studied. The microstructure of the samples were characterized by FESEM, XRD, UV-Vis, etc. The results show that RE doping can refine the grains and enhance the absorption of visible light. The performance of rare earth doped samples have a significantly improved compared with pure g-C3N4. The performance of La doped samples was better than that of Ce, Sm, Nd and Eu doped g-C3N4. As the temperature increases, the photocatalytic activity of La/g-C3N4 samples increases. When the La doping ratio is 4.0%, the calcination temperature is 590 °C, the degradation rate of The La/g-C3N4 photocatalyst to MB is up to 98.0% within 4 h under visible light irradiation.

The g-C3N4/BSA@MnO2 nanocomposites fluorescent off-on probe for detection and imaging of ascorbic acid in living cells

g-C3N4/BSA@MnO2 fluorescent off-on probe was constructed for sensitive and selective detection of ascorbic acid (AA). BSA@MnO2 nanoparticles using bovine serum albumin (BSA) as a template were anchored on the surface of graphite-phase carbon nitride nanosheets (g-C3N4 NSs) via electrostatic attraction to synthesize the g-C3N4/BSA@MnO2 nanocomposites. The fluorescence of g-C3N4 NSs was quenched by BSA@MnO2 nanoparticles (NPs) via fluorescence resonance energy transfer (FRET) and recovered in the presence of AA via the redox reaction between AA and MnO2. The nanocomposites therefore realized the fluorescent off–on detection of AA. Asatisfactory linear range of 0–120 μM and a limit of detection of 133 nM were obtained. The nanoprobe was applied for the detection of AA in food and drug samples as well as the fluorescent images of exogenous AA in Raw cells. The results showed that the nanoprobe possessed excellent properties for AA detection and broadened the biochemical analysis applications of g-C3N4-based nanomaterials.

Preparation and Photocatalytic Degradation Performance of Amine-Rich Carbon Nitride with Structural Modulation of the Precursor.

The photocatalytic performance of graphitic phase carbon nitride (g-C3N4) is strongly influenced by its own microstructure as well as the precursor structure that causes the microstructure changes. In this paper, a composite precursor of sodium chloride and cyanamide (NaCl/CA-2) was obtained by freeze-drying, which possess an aggregated state different from that of the non-freeze-drying method. This new aggregation state with the introduction of sodium ions into the cyanamide lattice results in a higher activation energy of NaCl/CA-2 in the thermal polycondensation process of the molten salt-assisted preparation of g-C3N4, which prevented the condensation of two cyanamides to one dicyandiamide, ultimately obtaining FD-CN with an amino-rich structure. The nitrogen atoms on the amino group can provide the photocatalyst with more unpaired electrons that can participate in the photoexcitation process, further improving its electron-hole separation ability and charge transfer efficiency, thus effectively enhancing its photocatalytic activity. Compared to the original g-C3N4, the photocatalytic activity of FD-CN for the degradation of methylene blue increased 2.19 times.

Solvothermal synthesis of g-C3N4 nanosheets modified carbon quantum dots for enhanced photocatalytic degradation

The incorrect disposal of industrial waste water has caused widespread concern of researchers due to its serious harm to people's health and ecological environment. Photocatalytic technology is widely used for wastewater purification owing to its simple operation, no secondary pollution and clean energy. In this study, carbonaceous composites were constructed by combining graphite-phase carbon nitride (g-C3N4) nanosheets with carbon quantum dots (CQDs) via hydrothermal method. The size of CQDs was about 8 nm, distributing over the surface of g-C3N4 nanosheets, and the existence of their interface interaction was confirmed. The photocatalytic degradation of methyl orange (MO) is considered to appraise the photocatalytic performance of the g-C3N4/CQDs composites under visible light. The obtained composites display better photocatalytic activity than the pure g-C3N4 nanosheets. The obtained g-C3N4/CQDs composite (CN-20) from 20 mL of the CQDs solution (∼1 mg mL−1) and 20 mg of g-C3N4 nanosheets displays the excellent photo-degradation efficiency and its apparent rate constant (kapp) is 4.0 times that of g-C3N4 nanosheets. In addition, CN-20 exhibits almost negligible influences of real environmental (pH value, inorganic anions, humic acid and source of water) on the degradation of MO, indicating potential in practical application. Furthermore, the g-C3N4/CQDs composite shows the enhanced cycle stability and the postulated mechanism of MO photocatalytic degradation is illustrated in detail.