Ultrafast synthesis of near-zero-cost S-doped Ni(OH)2 on C3N5 under ambient conditions with enhanced photocatalytic activity

2D S–Ni(OH)2 is facially planted on 2D C3N5 at room temperature in 30 minutes via a reaction between Ni(NO3)2 and Na2S in aqueous solution. Due to quick internal charge transfer efficiency, the hybrid is highly efficient for photocatalytic H2 production.

Metal-doped carbon nitrides: synthesis, structure and applications

This perspective provides a comprehensive overview of the latest progress of M–CN, which would promote further development, such as for single-atom catalysis and nanozymatic reactions.

Bio-based and Degradable Block Polyester Pressure-Sensitive Adhesives

A new class of bio-based fully degradable block polyesters are pressure-sensitive adhesives. Bio-derived monomers are efficiently polymerized to make block polyesters with controlled compositions. They show moderate to high peel adhesions (4-13 N cm-1 ) and controllable storage and loss moduli, and they are removed by adhesive failure. Their properties compare favorably with commercial adhesives or bio-based polyester formulations but without the need for tackifier or additives.

Superior antibacterial activity of sulfur-doped g-C3N4 nanosheets dispersed by Tetrastigma hemsleyanum Diels & Gilg's polysaccharides-3 solution

Bacterial resistance has become a serious global health issue over the past decades due to the misuse and abuse of antibiotics. The development of effective antibacterial drugs with a new antibacterial mechanism is thus very critical. At present, there are many reports on the antibacterial properties and mechanisms of two-dimensional materials. Currently, the modification of g-C₃N₄ materials, as widely used two-dimensional materials, has become a key step in extending their potential applications in the field of antimicrobial therapy. In the present work, we prepared sulfur-doped g-C₃N₄ nanosheets (SCNNSs), which have good water dispersibility and sharp tips. The electrostatic interaction of SCNNSs with Tetrastigma hemsleyanum Diels & Gilg's polysaccharide-3 (THDG-3) provides a new strategy that can improve the killing efficiency of SCNNSs. In addition, THDG-3 can rapidly inhibit bacterial proliferation in the early stage of administration. Combined with the antibacterial activity of the SCNNSs, TPS/SCNNSs can inhibit bacteria for a long time. Scanning electron microscopy (SEM) observation of Escherichia coli (E. coli) after administration of the materials revealed that the bacterial cells were ruptured and their intracellular contents were completely separated from the cell membrane. Therefore, we speculate that the bactericidal mechanism of the TPS/SCNNSs probably involves cell membrane damage. In summary, TPS/SCNNSs achieve fast, long-term, dual-function bacteriostatic properties.

Biuret-A Crucial Reaction Intermediate for Understanding Urea Pyrolysis To Form Carbon Nitrides: Crystal-Structure Elucidation and In Situ Diffractometric, Vibrational and Thermal Characterisation

The crystal structure of biuret was elucidated by means of XRD analysis of single crystals grown through slow evaporation from a solution in ethanol. It crystallises in its own structure type in space group C2/c (a=15.4135(8) Å, b=6.6042(3) Å, c=9.3055(4) Å, Z=8). Biuret decomposition was studied in situ by means of temperature-programmed powder XRD and FTIR spectroscopy, to identify a co-crystalline biuret-cyanuric acid phase as a previously unrecognised reaction intermediate. Extensive thermogravimetric studies of varying crucible geometry, heating rate and initial sample mass reveal that the concentration of reactive gases at the interface to the condensed sample residues is a crucial parameter for the prevailing decomposition pathway. Taking these findings into consideration, a study on the optimisation of carbon nitride synthesis from urea on the gram scale, with standard solid-state laboratory techniques, is presented. Finally, a serendipitously encountered self-coating of the crucible inner walls by graphite during repeated synthetic cycles, which prove to be highly beneficial for the obtained yields, is reported.

Interfacial nanoarchitectonics for responsive cellular biosystems

The living cell can be regarded as an ideal functional material system in which many functional systems are working together with high efficiency and specificity mostly under mild ambient conditions. Fabrication of living cell-like functional materials is regarded as one of the final goals of the nanoarchitectonics approach. In this short review article, material-based approaches for regulation of living cell behaviors by external stimuli are discussed. Nanoarchitectonics strategies on cell regulation by various external inputs are first exemplified. Recent approaches on cell regulation with interfacial nanoarchitectonics are also discussed in two extreme cases using a very hard interface with nanoarchitected carbon arrays and a fluidic interface of the liquid-liquid interface. Importance of interfacial nanoarchitectonics in controlling living cells by mechanical and supramolecular stimuli from the interfaces is demonstrated.

Mesoporous Polymeric Cyanamide-Triazole-Heptazine Photocatalysts for Highly-Efficient Water Splitting

Conjugated polymers are promising light harvesters for water reduction/oxidation due to their simple synthesis and adjustable bandgap. Herein, both cyanamide and triazole functional groups are first incorporated into a heptazine-based carbon nitride (CN) polymer, resulting in a mesoporous conjugated cyanamide-triazole-heptazine polymer (CTHP) with different compositions by increasing the quantity of cyanamide/triazole units in the CN backbone. Varying the compositions of CTHP modulates its electronic structures, mesoporous morphologies, and redox energies, resulting in a significantly improved photocatalytic performance for both H₂ and O₂ evolution under visible light irradiation. A remarkable H₂ evolution rate of 12723 µmol h^-1 g^-1 is observed, resulting in a high apparent quantum yield of 11.97% at 400 nm. In parallel, the optimized photocatalyst also exhibits an O₂ evolution rate of 221 µmol h^-1  g^-1 , 9.6 times higher than the CN counterpart, with the value being the highest among the reported CN-based bifunctional photocatalysts. This work provides an efficient molecular engineering approach for the rational design of functional polymeric photocatalysts.

Strategies for development of nanoporous materials with 2D building units

It has already been realized that two-dimensional (2D) materials carry a great potential in energy conversion and storage, gas storage, chemical sensing, and many other applications closely related to human life. These applications benefit from a key feature of 2D materials, namely the large specific surface area, which however can be diminished significantly due to the tendency of these materials to restack. In this review, we revisit the strategies - including soft and hard templating - that have been developed for generating nanoporosity in 3D materials and demonstrate their adaptation for 2D materials using carbon nitride and graphene materials as examples. Owing to the 2D nature of the building units, a new type of nanopore can be generated by perforating the basal planes. These in-plane nanopores are essential in many emerging applications of 2D materials such as semipermeable membranes; hence, their creation methods, including post-synthesis activation, ion bombardment, electron beam drilling, and nanolithography, are worthy of a critical review. Lastly, techniques for preventing the restacking by fabricating 2D-0D, 2D-1D, and 2D-2D layer-by-layer composite structures are discussed. The goal is to promote the use of these methods for creating nanoporosity in more 2D materials.

Single-Step Synthesis of Mesoporous Carbon Nitride/Molybdenum Sulfide Nanohybrids for High-Performance Sodium-Ion Batteries

Molybdenum disulfide (MoS₂ ) is a promising candidate as a high-performing anode material for sodium-ion batteries (SIBs) due to its large interlayer spacing. However, it suffers from continued capacity fading. This problem could be overcome by hybridizing MoS₂ with nanostructured carbon-based materials, but it is quite challenging. Herein, we demonstrate a single-step strategy for the preparation of MoS₂ coupled with ordered mesoporous carbon nitride using a nanotemplating approach which involves the pyrolysis of phosphomolybdic acid hydrate (PMA), dithiooxamide (DTO) and 5-amino-1H-tetrazole (5-ATTZ) together in the porous channels of 3D mesoporous silica template. The sulfidation to MoS₂ , polymerization to carbon nitride (CN) and their hybridization occur simultaneously within a mesoporous silica template during a calcination process. The CN/MoS₂ hybrid prepared by this unique approach is highly pure and exhibits good crystallinity as well as delivers excellent performance for SIBs with specific capacities of 605 and 431 mAhg^-1 at current densities of 100 and 1000 mAg^-1 , respectively, for SIBs.

Nanostructured Carbon Nitrides for CO2 Capture and Conversion

Carbon nitride (CN), a 2D material composed of only carbon (C) and nitrogen (N), which are linked by strong covalent bonds, has been used as a metal-devoid and visible-light-active photocatalyst owing to its magnificent optoelectronic and physicochemical properties including suitable bandgap, adjustable energy-band positions, tailor-made surface functionalities, low cost, metal-free nature, and high thermal, chemical, and mechanical stabilities. CN-based materials possess a lot of advantages over conventional metal-based inorganic photocatalysts including ease of synthesis and processing, versatile functionalization or doping, flexibility for surface engineering, low cost, sustainability, and recyclability without any leaching of toxic metals from photocorrosion. Carbon nitrides and their hybrid materials have emerged as attractive candidates for CO₂ capture and its reduction into clean and green low-carbon fuels and valuable chemical feedstock by using sustainable and intermittent renewable energy sources of sunlight and electricity through the heterogeneous photo(electro)catalysis. Here, the latest research results in this field are summarized, including implementation of novel functionalized nanostructured CNs and their hybrid heterostructures in meeting the stringent requirements to raise the efficiency of the CO₂ reduction process by using state-of-the-art photocatalysis, electrocatalysis, photoelectrocatalysis, and feedstock reactions. The research in this field is primarily focused on advancement in the synthesis of nanostructured and functionalized CN-based hybrid heterostructured materials. More importantly, the recent past has seen a surge in studies focusing significantly on exploring the mechanism of their application perspectives, which include the behavior of the materials for the absorption of light, charge separation, and pathways for the transport of CO₂ during the reduction process.

Thermodynamically Stable Mesoporous C3 N7 and C3 N6 with Ordered Structure and Their Excellent Performance for Oxygen Reduction Reaction

Carbon nitrides with a high N/C atomic ratio (>2) are expected to offer superior basicity and unique electronic properties. However, the synthesis of these nanostructures is highly challenging since many parts of the CN frameworks in the carbon nitride should be replaced with thermodynamically less stable NN frameworks as the nitrogen content increases. Thermodynamically stable C₃ N₇ and C₃ N₆ with an ordered mesoporous structure are synthesized at 250 and 300 °C respectively via a pyrolysis process of 5-amino-1H-tetrazole (5-ATTZ). Polymerization of the precursor to the ordered mesoporous C₃ N₇ and C₃ N₆ is clearly proved by X-ray and electron diffraction analyses. A combined analysis including diverse spectroscopy and FDMNES and density functional theory (DFT) calculations demonstrates that the NN bonds are stabilized in the form of tetrazine and/or triazole moieties in the C₃ N₇ and C₃ N₆ . The ordered mesoporous C₃ N₇ represents the better oxygen reduction reaction (ORR) performances (onset potential: 0.81 V vs reversible hydrogen electrode (RHE), electron transfer number: 3.9 at 0.5 V vs RHE) than graphitic carbon nitride (g-C₃ N₄ ) and the ordered mesoporous C₃ N₆ . The study on the mechanism of ORR suggests that nitrogen atoms in the tetrazine moiety of the ordered mesoporous C₃ N₇ act as active sites for its improved ORR activity.

Metal-free highly efficient photocatalysts for overall water splitting: C3N5 multilayers

As a promising means of renewable energy storage, the production of molecular hydrogen and oxygen from photocatalytic water splitting has gained increasing interest. The optimal photocatalyst for water splitting should have high solar energy conversion efficiency and strong photocatalytic redox ability to drive the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, few photocatalysts have been reported to fulfil these two contradictive requirements. Here, we demonstrated from first-principles calculations that the recently synthesized two-dimensional carbon nitride (C₃N₅) multilayers can serve as promising candidates to reach this goal. The intrinsic electric field which is more pronounced in the multilayers alters the band alignment of the photocatalysts, making the HER and OER be driven solely by the photogenerated carriers. The thickness-dependent electronic band gap (2.95-2.16 eV) along with the high carrier mobility broadens the energy range of light absorption and promotes carrier separation and transfer, leading to high solar energy conversion efficiency. Our computational results offer not only low-cost, Earth-abundant and environmentally friendly photocatalysts but also a promising strategy for the design of photocatalysts for highly efficient overall water splitting without using sacrificial reagents.

Electron Deficient Monomers that Optimize Nucleation and Enhance the Photocatalytic Redox Activity of Carbon Nitrides

Polymeric carbon nitride (PCN) is usually synthesized from nitrogen-rich monomers such as cyanamide, melamine, and urea, but is rather disordered in many cases. Now, a new allotrope of carbon nitride with internal heterostructures was obtained by co-condensation of very electron poor monomers (for example, 5-amino-tetrazole and nucleobases) in the presence of mild molten salts (for example, NaCl/KCl) to mediate the polymerization kinetics and thus modulate the local structure, charge carrier properties, and most importantly the HOMO and LUMO levels. Results reveal that the as-prepared NaK-PHI-A material shows excellent photo-redox activities because of a nanometric hetero-structure which enhances visible light absorption and promotes charge separation in the different domains.

Urea and Melamine Formaldehyde Resin-Derived Tubular g-C3N4 with Highly Efficient Photocatalytic Performance

Construction of various nanostructure g-C₃N₄, especially those with a tubular structure, is gaining considerable research interest because of their large specific surface area, high carrier transport efficiency, and excellent mass transfer. In this study, a novel multistage tubular g-C₃N₄ (TCN) has been prepared by the copolymerization of melamine formaldehyde (MF) resin with urea. With the introduction of MF resin, the electrostructure of TCN and its hydrophilicity property have been obviously ameliorated, thereby enhancing its visible-light absorption and improving the interface contact between TCN and water. Moreover, photocurrent response and electrochemical impedance spectra indicate that the special multistage tubular structure facilitates the spatial charge transfer and photogenerated carrier separation. Thus, the as-prepared TCN exhibits excellent photoactivities under visible-light irradiation. Among the samples, TCN-0.1 shows the best performance. Its hydrogen evolution rate is approximately 7505 μmol·g^-1·h^-1, which is 6.05 times greater than that of g-C₃N₄ (prepared by urea at 600 °C), and its apparent quantum efficiency is nearly 19.2% at 400 nm. In addition, TCN is also endowed with outstanding visible-light performance and durability for the degradation of tetracycline and methyl orange. This work might provide a significant inspiration for the design of new, highly efficient g-C₃N₄-based materials and further deepen our understanding of the preparation of tubular photocatalysts.

Sulfur-Doped Mesoporous Carbon Nitride with an Ordered Porous Structure for Sodium-Ion Batteries

Mesoporous carbon nitride (MCN) with well-ordered porous structures is a promising anode material for secondary ion batteries owing to their unique physico- and electrochemical properties. However, the practical application of these MCNs in sodium-ion batteries (SIBs) is still limited because of their confined interlayer distance, which results in restricted accommodation of Na ions inside the lattice. Here, we report on the synthesis of highly ordered sulfur-doped MCN (S-MCN) through a hard template approach by employing dithiooxamide (DTO) as a single molecular precursor containing carbon, nitrogen, and sulfur elements. The interlayer distance of carbon nitride is significantly expanded upon the introduction of larger S ions on the MCN lattice, which enables high capability of Na ion accommodation. We also demonstrate through the first-principles density functional theory calculation that the present S-MCN is highly optimized not only for the chemical structure but also for uptaking abundant Na ions with high adsorption energy. The specific discharge capacity of SIBs appears to be remarkably enhanced for S-MCN (304.2 mA h g^-1) compared to the nonporous S-CN (167.9 mA h g^-1) and g-C₃N₄ (5.4 mA h g^-1), highlighting the pivotal roles of the highly ordered mesoporous structure and S-doping in enhancing the electrochemical functionality of carbon nitride as an anode material for SIBs.

A Facile and Green Combined Strategy for Improving Photocatalytic Activity of Carbon Nitride

We first report an efficient combined strategy that simultaneously integrates copolymerization, doping, and molecular self-assembly for the development of carbon-doping petal-like carbon nitride photocatalysts using melamine (MA), cyanuric acid (CA), and 2,4,6-triaminopyrimidine (TAP) as the starting precursors and water as the only green solvent. The morphology, textural, optical, and electronic properties of carbon nitride could be engineered by rationally manipulating the doping content of TAP. In the process of molecular self-assembly, TAP can insert the aggregate edge easily according to the results of density functional theory (DFT) calculations. The edge-termination effect of TAP made it easier for the modified carbon nitride materials to form petal-like nanosheets with porous structures and large BET surface areas. In addition, the incorporation of TAP also contributed to tuning the electronic band structures of carbon nitrides and enhancing the separation efficiency of photogenerated carriers. The as-prepared materials exhibited excellent photocatalytic activities in the degradation of tetracycline hydrochloride (TC-HCl) and rhodamine B (RhB). This work may not only offer universally powerful and stable photocatalysts for applications but also develop a new combined strategy to fabricate efficient photocatalysts in a facile and green way.