Mesoporous Carbon Nitride Research Articles

Single-atom Ir and Ru anchored on graphitic carbon nitride for efficient and stable electrocatalytic/photocatalytic hydrogen evolution

Renewable energy-powered water electrolysis and photocatalytic water splitting are two promising approaches to green hydrogen production. Electrocatalysts and photocatalysts are essential components determining the performance of water electrolyzers and photocatalytic reactors, respectively. Currently, there is a pressing need to develop efficient and stable electrocatalysts and photocatalysts for large-scale deployment of these devices to reach carbon neutrality. Herein, we report the synthesis of single-atom Ir and Ru anchored on mesoporous graphitic carbon nitride (Ir-g-CN and Ru-g-CN), which can be used as electrocatalysts and photocatalysts for the hydrogen evolution reaction (HER). Remarkably, Ru-g-CN shows a high turnover frequency (TOF) of 12.9 and 5.1 s−1 at an overpotential (η) of 100 mV in 0.5 M H2SO4 and 1.0 M KOH, respectively, outperforming Ir-g-CN, commercial Pt/C benchmark and many other advanced HER catalysts reported recently. Moreover, Ru-g-CN can deliver an exceptionally high mass activity of 24.55 and 8.78 A mg−1 at η = 100 mV in acidic and alkaline solutions, meanwhile exhibiting a high apparent current density, which is favorable for practical applications. Additionally, both Ru-g-CN and Ir-g-CN show outstanding catalytic stability, continuously catalyzing the HER in acidic and alkaline conditions for 120 h with minimal degradation. Besides, when used for photocatalytic water splitting, Ru-g-CN can achieve a high hydrogen production rate of 489.7 mmol H2 gRu−1 h−1, and shows good photocatalytic stability. Our density functional theory (DFT) calculations demonstrate that loading Ir and Ru single-atoms on g-CN alters the electronic structure, resulting in a reduced bandgap and improved electrical conductivity, facilitating electron transfer during the catalysis. Moreover, the Gibbs free energy of hydrogen adsorption on Ru-g-CN and Ir-g-CN is also substantially lowered, enhancing HER performance.

Enhanced the Synergistic Effect of Tetracycline Adsorption and Photocatalytic Degradation on a Mesoporous Carbon Nitride

Enhanced the Synergistic Effect of Tetracycline Adsorption and Photocatalytic Degradation on a Mesoporous Carbon Nitride

One-step fabrication of mesoporous sulfur-doped carbon nitride for highly selective photocatalytic transformation of native lignin to monophenolic compounds

Photocatalytic selective transform native lignin into valuable chemicals is an attractive but challenging task. Herein, we report a mesoporous sulfur-doped carbon nitride (MSCN-0.5) which is prepared by a facile one-step thermal condensation strategy. It is highly active and selective for the cleavage Cα−Cβ bond in β−O−4 lignin model compound under visible light radiation at room temperature, achieving 99% substrate conversion and 98% Cα−Cβ bond cleavage selectivity. Mechanistic studies revealed that the Cβ−H bond of lignin model compounds activated by holes and generate key Cβ radical intermediates, further induced the Cα−Cβ bond cleavage by superoxide anion radicals (•O2−) to produce aromatic oxygenates. Waste Camellia oleifera shell (WCOS) was taken as a representative to further understand the reaction mechanisms on native lignin. 33.2 mg of monophenolic compounds (Vanillin accounted for 22% and Syringaldehyde for 34%) can be obtained by each gram of WCOS lignin, which is 2.5 times as that of the pristine carbon nitride. The present work offers useful guidance for designing metal-free heterogeneous photocatalysts for Cα−Cβ bond cleavage to harvest monophenolic compounds.

Azide-Alkyne Click Chemistry over a Heterogeneous Copper-Based Single-Atom Catalyst

One-pot three-component regioselective azide-alkyne cycloadditions are central reactions for synthesizing pharmaceuticals and fine chemicals and are also applied for in vivo metabolic labeling biotechnology. Homogeneous catalysts based on copper species coordinated with ancillary ligands are regularly used to perform this reaction, offering superior catalytic activity and selectivity compared to conventional heterogeneous counterparts based on supported copper nanoparticles. However, the challenge of catalyst recovery limits the use of these homogeneous compounds in many large-scale applications. In this work, we report the high catalytic performance of a family of Cu-based single-atom catalysts for triazole synthesis, with an emphasis on the fundamental understanding of the structure and function of the catalyst. The catalysts were prepared via tricyanomethanide polymerization to create a joint electronic structure where the mesoporous graphitic carbon nitride carrier acts as a ligand for the atomically dispersed copper species. The material properties and the precise metal location/coordination (i.e., deposited in the heptazine pore of carbon nitride, substituted in the framework of carbon nitride, hosted in a vacancy, or entrapped in sandwich-like arrangement) were characterized through a battery of spectroscopic and theoretical methods. The catalysts were employed in the synthesis of 1,2,3-triazoles employing azide-alkyne click reaction under base-free conditions. The single-atom Cu catalysts demonstrated improved activity and selectivity compared to the homogeneous reference catalyst. Density functional theory calculations corroborated the results and showed that the reaction proceeds through a barrier given by the activation of the acetylenic moiety on Cu1. The activity of this step was primarily affected by the coordination of the metal with the support. Therefore, understanding the metal coordination in single-atom catalysts is critical to further optimizing single-atom catalysts and greening synthetic chemistry.

Preparation of non-polluting Tb-doped mesoporous carbon nitridephotocatalyst and study on the efficacy and mechanism of degradation of antibiotics in water.

Given that the biological treatment of antibiotic wastewater can easily induce resistant bacteria, the photocatalytic degradation of antibiotics is considered as a better method for treating antibiotic wastewater. Therefore, the ability to remove Tylosin (TYL) and Tetracycline (TC) in aqueous solution using rare earth element Tb-doped g-C3N4 under simulated natural solar radiation was investigated. A series of rare earth Tb3+ doped mesoporous g-C3N4 were successfully prepared by nitric acid treatment and Tb(NO3)3·5H2O samples showed significantly higher degradation efficiency for TYL and TC than pure g-C3N4. Leaching toxicity experiments were carried out on the catalyst using chard seeds and demonstrated negligible toxicity of the leachate from the catalyst. The structure, elemental state, optical properties, morphology, and photogenerated carrier separation of the prepared xTCN catalysts were characterized by XRD, XPS, UV-Vis DRS, TEM, and PL. The results show that Tb doping enhanced the photocatalytic activity of the g-C3N4 catalyst by narrowing the band gap while improving the light-trapping ability; The separation and transport rate of photogenerated carriers were significantly increased after Tb doping. Finally, a simple, efficient, and non-polluting Tb-doped carbon nitride photocatalyst is successfully developed in this paper.

Polydopamine/defective ultrathin mesoporous graphitic carbon nitride nanosheets as Z-scheme organic assembly for robust photothermal-photocatalytic performance

Polydopamine/defective ultrathin mesoporous graphitic carbon nitride (PDA/DCN) Z-scheme organic assembly is fabricated through high-temperature surface hydrogenation and ultrasonic freeze-dried strategies. PDA could be anchored on the surface of DCN with adequate N-vacancy defects firmly via π-π interactions, forming Z-scheme heterogenous structure for promoting charge separation. The visible and near-infrared light driven photocatalytic hydrogen evolution rate is up to 3420 μmol h−1 g−1, and the removal ratio of organic contaminant methylene blue is up to 98% within 70 min, which is several times higher than that of pristine graphitic carbon nitride and DCN. The important reason is the defects of DCN not only enhance the interaction with PDA, but also make the obvious polarized inbuilt electric field, and lead to Z-scheme structure for effective charge separation and rapid transfer, which is also confirmed by density functional theory (DFT) calculations. In addition, PDA extends the photoresponse to the near-infrared region and induces obvious photothermal effect to increase the reaction rate of the photocatalytic system. The efficient photothermal conversion of PDA/DCN should be another reason for the enhanced photocatalytic performance.

Insight into the photodegradation mechanism of bisphenol-A by oxygen doped mesoporous carbon nitride under visible light irradiation and DFT calculations.

Oxygen doped mesoporous carbon nitride (O-MCN) was successfully synthesized through one-step thermal polymerization of urea and glucose utilizing nanodisc silica (NDS) from rice husk ash as a hard template. The CO2 gas, NH3 and water vapor produced during the thermal process reshaped the morphology and textural properties of the of O-MCN compared to pristine mesoporous carbon nitride (MCN). Highest bisphenol A (BPA) removal achieved under visible light irradiation was 97%, with 60% mineralization ([BPA] = 10 mg L−1: catalyst dosage = 40 mg L−1; pH = 10; 180 min). In addition to mesoporosity, the sub-gap impurity states created from the oxygen doping reduced recombination rate of photogenerated carriers. Holes (h+) and superoxide (O2˙−) were identified as the predominant active species responsible for the photodegradation process. The photodegradation route was proposed based on the intermediates detected by LC-time-of-flight/mass spectrometry (LC/TOF-MS). The Density of States (DOS) showed that oxygen doping resulted in a higher photoactivity due to the stronger localization and delocalization of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). The adsorption pathway of the BPA on the O-MCN and MCN was successfully predicted using the DFT calculations, namely molecular electrostatic potential (MEP), global and local descriptors.

Insights into the light-driven hydrogen evolution reaction of mesoporous graphitic carbon nitride decorated with Pt or Ru nanoparticles.

Ru or Pt nanoparticles have been prepared following the organometallic approach and deposited onto the surface of mesoporous graphitic carbon nitride (mpg-CN). Three different Ru-based samples have also been compared to investigate the effect of 4-phenylpyridine as a stabilizing agent. The photocatalytic performance towards the hydrogen evolution reaction (HER) has been tested showing that all hybrid systems clearly outperform the photocatalytic activity of bare mpg-CN. In particular, Pt-decorated mpg-CN yields the largest H2 production upon visible-light irradiation (870 μmol h-1 g-1, TOF = 14.1 h-1, TON = 339 after 24 h) when compared with the Ru-based samples (137-155 μmol h-1 g-1, TOFs between 2.3-2.7 h-1, TONs between 54-57 after 24 h). Long-term photochemical tests (up to 65 h irradiation) show also an improved stability of the Pt-based samples over the Ru counterpart. Photophysical experiments aimed at rationalizing the photocatalytic performance of the different hybrid systems elucidate that the enhanced activity of the Pt-decorated mpg-CN over the Ru-based analogues arises from improved electron transfer kinetics from mpg-CN to the metal nanoparticles.

Facile synthesis of mesoporous polymeric carbon nitride nanosheets anchored by Pt with ultralow loading for high-efficiency photocatalytic H2 evolution.

The facile fabrication of low-cost photocatalysts with enhanced activity and high atomic utilization is becoming increasingly necessary for solar energy usage and/or conversion. In this work, a series of mesoporous carbon nitride nanosheets with an enlarged specific surface area was synthesized via an inorganic acid-assisted exfoliation method without any soft or hard templates. An ultralow loading of downsized noble metal Pt was anchored on these porous nanosheets, exhibiting enhanced photocatalytic activity. The formation of mesoporous nanosheets in carbon nitride was expected to boost the mass transfer and shorten the charge carrier transfer route during the photocatalytic reaction. The characterization of samples revealed that the enhanced conductivity and photocurrent of the carbon nitride nanosheets also contributed to the enhanced H2 evolution activity. The maximum H2 production rates of 172.92 μmol h-1 and 321 μmol h-1 were achieved over the nanosheets derived from melamine and urea under visible light irradiation, which are 10.92- and 2.22-fold that of the corresponding bulk carbon nitride, respectively. This exfoliation method was demonstrated to be an efficient and universal method for the preparation of carbon nitride nanosheets with a mesoporous structure and high atom utilization of the co-catalyst for H2 evolution from water.

Photocatalytic valorization of furfural to value-added chemicals via mesoporous carbon nitride: a possibility through a metal-free pathway

Renewable solar light-driven biomass furfural valorization.

3D-phosphorus doped mesoporous graphitic carbon nitride based immunosensor for swine flu detection

Illustrative representation of the immunosensing platform and its electrochemical response for the detection of swine flu.

Copper loaded nitrogen-rich mesoporous carbon nitride as a highly efficient photocatalyst for selective oxidative cleavage of C(sp3)–C(sp3) bonds at room temperature under visible light

A newly designed copper loaded nitrogen-rich mesoporous carbon nitride for photocatalytic selective oxidative cleavage of C(sp3)–C(sp3) bonds at room temperature is presented.

Construction of brown mesoporous carbon nitride with a wide spectral response for high performance photocatalytic H2 evolution

A novel brown mesoporous carbon nitride photocatalyst is synthesized by a doping strategy. The excellent visible light response and stable mesoporous structure lead to an efficient hydrogen evolution activity.

Activation of ordered mesoporous carbon nitride prepared via soft-template for CO2 adsorption

A mesoporous carbon nitride material (MCN) was nanocasted by using a soft-template of triblock surfactant Pluronic F127, a carbon resource from resol and dicyandiamide (DCDA) as a nitrogen precursor. The obtained MCN was activated to improve its porous channel (AMCN). A reference sample of mesoporous carbon (MC) material was also prepared in the same protocol without DCDA. The tunable mesostructures (p6m symmetry) was proved by X-ray diffraction, transmission electron microscopy images and nitrogen adsorption-desorption isotherms. Fourier transformation infrared spectroscopy and energy dispersive X-ray spectroscopy presented about 3.1 wt% of doped-nitrogen in the obtained MCN. In comparison to the MC, a significant increase of BET surface area (333 m2/g for MC, 414 m2/g for MCN and 951 m2/g for AMCN) and an enlargement of pore volume (0.23 cm3/g for MC, 0.25 cm3/g for MCN and 0.33 cm3/g for AMCN), which contributed to a noticeable enhancement of the room temperature CO2 uptake from 1.8 mmol/g (for MC) to 3.7 mmol/g (for MCN) and 4.1 mmol/g (for AMCN). This work emphasized that the assistance of DCDA and further activation resulted in enlargement of both pore volume and BET surface area promising a feasible application of MCN and AMCN in adsorption technology.

Chemoselective reduction of α,β-unsaturated carbonyl compounds in the presence of CuPd alloy nanoparticles decorated on mesoporous graphitic carbon nitride as highly efficient catalyst

Herein, we reported reductions of acid, amide, ester and ketone groups with selectivity (>99%) by the catalytic transfer hydrogenation of with CuPd alloy nanoparticles (NPs) decorated on mesoporous graphitic carbon nitride (Cu50Pd50/mpg-C3N4) catalyst under mild conditions in a water/methanol mixture. CuPd alloy NPs were synthesized by the co-reduction of palladium (II) acetylacetonate and copper(II) acetylacetonate in oleylamine (OAm) solution by the reduction of morpholine-borane solution and then assembled on mpg-C3N4 via liquid phase self‐assembly method. The α, β-unsaturated carbonyl compounds were obtained from the condensation reaction of the benzaldehyde derivatives with acetone derivatives. Cu50Pd50/mpg-C3N4 nanocatalyst was characterized by TEM, XRD, XPS, BET and ICP‐MS. Cu50Pd50/mpg-C3N4 nanocatalyst is highly active catalyst for the reduction of various organic groups and converted to high yield and 99% selectivity. The superior Cu50Pd50/mpg-C3N4 nanocatalyst is highly efficient and reusable catalyst which is reuse after 5 cycle with 98% conversion.

Fe atom clusters embedded N-doped graphene decorated with ultrathin mesoporous carbon nitride nanosheets for high efficient photocatalytic performance

Atomic-level dispersed non-noble metal co-catalyst offers high potential for improving photocatalytic performance. Herein, Fe atom clusters embedded N-doped graphene (Fe-NG) stacked ultrathin mesoporous carbon nitride nanosheets (MCNS) by layer and layer that have been successfully constructed. The Fe-NG as co-catalyst can promote the effective migration of photogenerated electrons on the surface of MCNS nanosheets, thus effectively separate photogenerated carriers. Moreover, the metal atom clusters sites can absorb more reactants, which is conducive to the promotion of photocatalytic reaction. The photocatalytic activity of these composites was tested under visible light irradiation with the indissoluble antibiotics, endocrine disruptors and dyes as the target pollutants. When the mass ratios of Fe are about 0.15 wt.%, the Fe-NG/MCNS exhibited the optimum photocatalytic performance. The intermediates of various pollutants produced during the photodegradation reaction and corresponding possible degradation pathway were in-depth analyzed with mass spectrometry spectra. The ESR analysis indicated that the •O2− and •OH were the main active species for the photocatalytic degradation. A possible mechanism of Fe-NG for the enhancement of visible light performance was proposed. Meanwhile, the Fe-NG/MCNS composite shows promising application for the photo-oxidative degradation of environmental contaminants.

Photocatalytic C-H Azolation of Arenes Using Heterogeneous Carbon Nitride in Batch and Flow.

The functionalization of aryl C(sp2)−H bonds is a useful strategy for the late‐stage modification of biologically active molecules, especially for the regioselective introduction of azole heterocycles to prepare medicinally‐relevant compounds. Herein, we describe a practical photocatalytic transformation using a mesoporous carbon nitride (mpg‐CN x ) photocatalyst, which enables the efficient azolation of various arenes through direct oxidation. The method exhibits a broad substrate scope and is amenable to the late‐stage functionalization of several pharmaceuticals. Due to the heterogeneous nature and high photocatalytic stability of mpg‐CN x , the catalyst can be easily recovered and reused leading to greener and more sustainable routes, using either batch or flow processing, to prepare these important compounds of interest in pharmaceutical and agrochemical research.

Synergistic effect of isolated Co and Fe dual active sites boosting the photocatalytic hydrogen evolution reaction

The photocatalytic hydrogen evolution reaction is a promising and powerful approach to replace traditional fossil fuels. Herein, we have fabricated Fe, Co dual single atoms dispersed on nitrogen-doped graphene ((Fex, Coy)-NG) by freeze-drying method, which can as a highly efficient co-catalyst. The (Fex, Coy)-NG loaded mesoporous graphitic carbon nitride (mpg-C3N4) exhibits an excellently high performance for photocatalytic hydrogen evolution. The high activity can belong to two ways: (i) the ultrathin mpg-C3N4 not only increases the absorption and active sites but also shortens the charge migration distance; (ii) The nitrogen functional groups from NG can provide abundant coordination sites to evenly bind Fe and Co atoms. The photocatalytic hydrogen evolution performances (Fex, Coy)-NG co-catalyst with different content ratios of Fe atoms and Co atoms were also investigated. The optimized hydrogen production rate (1958 μmol g−1) of 5 wt% (Fe0.2, Co0.8)-NG/mpg-C3N4 is obviously higher compared to the monometallic counterparts (5 wt% Fe-NG/mpg-C3N4 or 5 wt% Co-NG/mpg-C3N4). The higher photoactivities are due to the synergistic effect between Fe and Co.

Mesoporous graphitic carbon nitride for adsorptive desulfurization in an isooctane solution

g-C3N4, a typical 2D material, has been developed as a promising desulfurization adsorbent, and the effect of preparation temperature on the adsorption performance was investigated here. Mesoporous g-C3N4 was synthesized by a hard template method with gel silica as the template agent. The precursor powder was heat-treated for 4 h at different temperatures (500°C, 550°C and 600°C), respectively, named CN-500, CN-550 and CN-600. UV-Vis spectra and X-ray photoelectron spectroscopy spectra prove CN-500 is composed of triazine g-C3N4, whereas CN-600 is partially composed of tri-s-triazine g-C3N4. The max adsorption capacity of CN-600 toward thiophene (TP) is up to 40.82 mg S/g in an isooctane solution, while CN-500 with the maximum specific surface area of 176.5 m2/g shows better selectivity but a smaller adsorption capacity. The robust adsorptive performance of mesoporous g-C3N4 is attributed to the D-A (Donor–Acceptor) interactions between adsorbent and TP, which could be interfered by the π–π interactions or steric effect, leading to a variable adsorptive capacity or selectivity towards TP and its analogs.

Ascorbic acid-assisted hydrothermal route to create mesopores in polymeric carbon nitride for increased photocatalytic hydrogen generation

The facile synthesis of mesoporous polymeric carbon nitride (PCN) can enlarge the surface area and provide mass transport channels, which thus potentially boosts its photocatalytic H2 generation. However, the formation of mesopores in PCN are mainly relying on the hard and soft templates with tedious operations, and it remains a grand challenge in preparing mesoporous PCN without the assistance of templates. Herein we report on an ascorbic acid-assisted hydrothermal route to effectively create the mesoporous in bulk PCN. The mesopores thus formed a typical IV isotherm with an H3 hysteresis loop, and have a pore size distribution of ∼3.8 nm. Moreover, the crystallinity of mesoporous PCN was improved with ascorbic acid-assisted hydrothermal treatment. Meanwhile, ascorbic acid can be converted to carbon materials under hydrothermal conditions. As a result, an increased photocatalytic H2 generation was realized under visible light exposure. The highest H2 generation rate is up to 26.8 μmol h−1 for Pt/CN-A10%, near 10 times higher than that of Pt/PCN (2.7 μmol h−1). This work highlights the effectiveness of organic acid-assisted hydrothermal treatment for synthesizing mesoporous PCN for increased photocatalytic performance.