Preparation of N-Graphdiyne Nanosheets at Liquid/Liquid Interface for Photocatalytic NADH Regeneration

Tailoring the Electronic Structure and Properties of Graphdiyne by Cyano Groups

Two-dimensional (2D) materials, such as 2D carbon-based systems, have been recently the subject of intense studies, thanks to their optoelectronic properties and promising electronic performances. 2D carbon-based materials such as graphdiyne (GDY) represent an optimal platform for tuning the optoelectronic properties via precise chemical functionalization. Here, we report a synthetic strategy to precisely introduce cyano groups into the 2D GDY backbone in order to tune the electronic properties of GDY. Three kinds of cyano-modified GDY have been synthesized, namely, bearing one cyano group (CNGDY), two CN in meta (m-CNGDY), and two in para (p-CNGDY) positions. A variety of experimental data as well as first-principles calculations allowed us to elucidate the role of the cyano groups in tuning the structural and functional properties of GDYs. We found that an increase in the number of cyano groups reduces the interlayer spacing between GDY layers, increases the lithium adsorption amount, as well as impacts the lithium diffusion rate, while changes in meta- or para-position impact the energy band gap.

Properties, Synthesis and Emerging Applications of Graphdiyne: A Journey Through Recent Advancements

Graphdiyne (GDY) is a new variant of nano-carbon material with excellent chemical, physical and electronic properties. It has attracted wide attention from researchers and industrialists for its extensive role in the fields of optics, electronics, bio-medics and energy. The unique arrangement of sp-sp2 carbon atoms, linear acetylenic linkages, uniform pores and highly conjugated structure offer numerous potentials for further exploration of GDY materials. However, since the material is at its infancy, not much understanding is available regarding its properties, growth mechanism and future applications. Therefore, in this review, readers are guided through a brief discussion on GDY's properties, different synthesis procedures with a special focus on surface functionalization and a list of applications for GDY. The review also critically analyses the advantages and disadvantages of each synthesis route and emphasizes the future scope of the material.

Microwave assisted synthesis of PQ-GDY@NH2-UIO-66(Zr) for improved photocatalytic removal of NOx under visible light

Pyrazinoquinoxaline-based graphdiyne (PQ-GDY) contains a fixed number of sp-sp2 hybridized carbon atoms and pyrazine-like sp2 hybridized N atoms. In this paper, NH2-UIO-66(Zr) on PQ-GDY substrate was successfully constructed with the help of microwave-assisted heating. PQ-GDY surface acts as a microwave antenna under microwave irradiation to rapidly absorb microwave energy and form hot spots (hot spot effect), which facilitates the formation of well-dispersed NH2-UIO-66(Zr) with good crystallinity. Transient absorption spectra show that high hole transport property of PQ-GDY can accelerate the migration of photogenerated holes from NH2-UIO-66(Zr) to PQ-GDY and greatly reduce the recombination rate of photogenerated electrons and holes due to the strong interaction between PQ-GDY and NH2-UIO-66(Zr). Under visible light (λ ≥ 420 nm), PQ-GDY@NH2-UIO-66(Zr) shows high photocatalytic stability and high NOx removal rate up to 74%, which is 44% higher than that of primitive NH2-UIO-66(Zr). At the same time, it inhibits the formation of toxic by-products (NO2) and limits its concentration to a low level.

Two-Dimensional Carbon Graphdiyne: Advances in Fundamental and Application Research

Graphdiyne (GDY), a rising star of carbon allotropes, features a two-dimensional all-carbon network with the cohybridization of sp and sp² carbon atoms and represents a trend and research direction in the development of carbon materials. The sp/sp²-hybridized structure of GDY endows it with numerous advantages and advancements in controlled growth, assembly, and performance tuning, and many studies have shown that GDY has been a key material for innovation and development in the fields of catalysis, energy, photoelectric conversion, mode conversion and transformation of electronic devices, detectors, life sciences, etc. In the past ten years, the fundamental scientific issues related to GDY have been understood, showing differences from traditional carbon materials in controlled growth, chemical and physical properties and mechanisms, and attracting extensive attention from many scientists. GDY has gradually developed into one of the frontiers of chemistry and materials science, and has entered the rapid development period, producing large numbers of fundamental and applied research achievements in the fundamental and applied research of carbon materials. For the exploration of frontier scientific concepts and phenomena in carbon science research, there is great potential to promote progress in the fields of energy, catalysis, intelligent information, optoelectronics, and life sciences. In this review, the growth, self-assembly method, aggregation structure, chemical modification, and doping of GDY are shown, and the theoretical calculation and simulation and fundamental properties of GDY are also fully introduced. In particular, the applications of GDY and its formed aggregates in catalysis, energy storage, photoelectronic, biomedicine, environmental science, life science, detectors, and material separation are introduced.

Nitrogen and fluoride co-doped graphdiyne with metal-organic framework (MOF)-derived NiCo2O4-Co3O4 nanocages as sensing layers for ultra-sensitive pesticide detection

Heteroatom doped graphdiyne (GDY) has been demonstrated to be an effective strategy for achieving outstanding electrochemical properties, including improved electrocatalytic activity, tunable electronic properties and high electronic conductivity, by producing numerous heteroatomic defects as well as active sites. Extensive efforts have been devoted to the issue of single element doping of GDY. Introducing two or more kinds of heteroatoms into GDY materials may create a synergic effect between the co-dopants, thus generating superior electrochemical performance. Nevertheless, little research on multiple elements co-doped GDY, especially in the application of constructing electrochemical biosensor. Herein, nitrogen and fluoride co-doped GDY (N-F-GDY) has been synthesized and employed to combine with NiCo₂O₄-Co₃O₄ hollow multishelled nanocages to establish an ultrasensitive electrochemical biosensor for the assay of pesticide residue. The as-prepared electrochemical biosensor possesses a wide linear range of 0.448 pM-44.8 nM for monocrotophos detection and a low detection limit of 0.0166 fM (S/N = 3).

Rapid and Reversible Sensing Performance of Hydrogen-Substituted Graphdiyne

The design of new nanomaterials for rapid and reversible detection of molecules in existence is critical for real-world sensing applications. Current nanomaterial libraries such as carbon nanotubes, graphene, MoS₂, and MXene are fundamentally limited by their slow detection speed and small signals; thus, the atomic-level material design of molecular transport pathways and active binding sites must be accompanied. Herein, we fully explore the chemical and physical properties of a hydrogen-substituted graphdiyne (HsGDY) for its molecular sensing properties. This new carbon framework comprises reactive sp carbons in acetylenic linkages throughout the 16.3 Å nanopores and allows for detecting target molecules (e.g., H₂) with an exceptionally high sensitivity (ΔR/R_b = 542%) and fast response/recovery time (τ₉₀ = 8 s and τ₁₀ = 38 s) even without any postmodification process. It possesses 2 orders of magnitude higher sensing ability than that of existing nanomaterial libraries. We demonstrate that rapid and reversible molecular binding is attributed to the cooperative interaction with adjacent double sp carbon in the layered nanoporous structure of HsGDY. This new class of carbon framework provides fundamental solutions for nanomaterials in reliable sensor applications that accelerate real-world interfacing.

Interfacial Synthesis of an Ultrathin Two-Dimensional Polymer Film via [2 + 2] Photocycloaddition

A carbon-carbon-linked, ultrathin, two-dimensional (2D) polymer film was prepared at the air/water interface through photochemically triggered [2 + 2] cycloaddition. The preorganization of the monomers on the water surface and the subsequent photo-polymerization led to the successful preparation of the ultrathin 2D polymer film. The obtained film is continuous, free standing, and has a large area (over 50 μm²). Transmission electron microscopy (TEM) and atomic force microscopy (AFM) give clear evidence of the ultrathin film morphology. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) indicate successful photo-induced [2 + 2] polymerization.

Nanostructured Graphdiyne: Synthesis and Biomedical Applications

Graphdiyne (GDY) is a 2D carbon allotrope that features a one-atom-thick network of sp- and sp2-hybridized carbon atoms with high degrees of π conjugation. Due to its distinct electronic, chemical, mechanical, and magnetic properties, GDY has attracted great attention and shown great potential in various fields, such as catalysis, energy storage, and the environment. Preparation of GDY with various nanostructures, including 0D quantum dots, 1D nanotubes/nanowires/nanoribbons, 2D nanosheets/nanowalls/ordered stripe arrays, and 3D nanospheres, greatly improves its function and has propelled its applications forward. High biocompatibility and stability make GDY a promising candidate for biomedical applications. This review introduces the latest developments in fabrication of GDY-based nanomaterials with various morphologies and summarizes their propective use in the biomedical domain, specifically focusing on their potential advantages and applications for biosensing, cancer diagnosis and therapy, radiation protection, and tissue engineering.

Electrocatalytic NAD+ reduction via hydrogen atom-coupled electron transfer

Nicotinamide adenine dinucleotide cofactor (NAD(P)H) is regarded as an important energy carrier and charge transfer mediator. Enzyme-catalyzed NADPH production in natural photosynthesis proceeds via a hydride transfer mechanism. Selective and effective regeneration of NAD(P)H from its oxidized form by artificial catalysts remains challenging due to the formation of byproducts. Herein, electrocatalytic NADH regeneration and the reaction mechanism on metal and carbon electrodes are studied. We find that the selectivity of bioactive 1,4-NADH is relatively high on Cu, Fe, and Co electrodes without forming commonly reported NAD2 byproducts. In contrast, more NAD2 side product is formed with the carbon electrode. ADP-ribose is confirmed to be a side product caused by the fragmentation reaction of NAD+. Based on H/D isotope effects and electron paramagnetic resonance analysis, it is proposed that the formation of NADH on these metal electrodes proceeds via a hydrogen atom-coupled electron transfer (HadCET) mechanism, in contrast to the direct electron-transfer and NAD˙ radical pathway on carbon electrodes, which leads to more by-product, NAD2. This work sheds light on the mechanism of electrocatalytic NADH regeneration, which is different from biocatalysis.

Non-covalent metalation of carbon nitride for photocatalytic NADH regeneration and enzymatic CO2 reduction

An artificial photocatalyst with a Rh complex immobilized onto polymeric carbon nitride (CN) through non-covalent interaction was constructed for photocatalytic NADH regeneration. DFT calculations verified the adsorption of the bipyridine ligand onto the CN photocatalyst. By further coupling the in situ formed NADH with FDH immobilized on a hydrophobic membrane, an enhanced HCOOH production (3.1 mM) from CO₂ could be realized on the gas-liquid-solid three-phase interface. This work provides an alternative and efficient strategy for promoting artificial photosynthesis.

Enhanced Photocatalytic Efficiency in Visible-Light-Induced NADH Regeneration by Intramolecular Electron Transfer

Inspired by natural photosynthesis, photocatalytic NADH regeneration has drawn increasing interest in the recent decade as it provides a perfect approach for NAD⁺ reduction into NADH, which can be further consumed by oxidordeuctase for enzymatic redox reactions. However, two issues still remain unsolved in this procedure. First, the photocatalytic efficiency in NAD⁺ hydrogenation requires further improvement. Second, the rhodium electron mediator [Cp*Rh(bpy)H₂O]²⁺ (M), which is always required for selective 1,4-NADH regeneration, is difficult to recover because of its good solubility in aqueous solution. Given the high price of M, it is highly wasteful and inefficient if it only spends once. Here, we report a Cp*Rh(bpy)Cl implanted conjugated microporous polymer DTS/Rh@CMPs which can be employed as a highly effective visible light photocatalysts for in situ NADH regeneration without using additional M. In addition, the insertion of Rh complex into a polymer skeleton, as demonstrated in UV-vis, fluorescence, photocurrent and electrochemical impedance, dramatically improves the light absorption capacity and the electron separation and transfer efficiency. Compared with that of DTS@CMP-1 with M, an enhanced reaction yield of 33% was determined in DTS/Rh@CMP-1 suggesting that intramolecular electron transfer has a better activity than that of intermolecular electron transfer in photocatalytic NAD⁺ reduction. Moreover, as the Rh complex is rooted firmly in a polymer framework, negligible Rh loss and conversion decrease in NADH regeneration are observed. When the DTS/Rh@CMP-1 was coupled with yeast alcohol dehydrogenase (YADH, from Saccharomyces cerevisiae), 1.36 mM of methanol was accumulated, implying an excellent biocompatibility of DTS/Rh@CMP-1 and a high feasibility of photobiocatalysis for formaldehyde hydrogenation.

Graphdiyne Electrochemistry: Progress and Perspectives

Graphdiyne, a carbon allotrope, was synthesized in 2010 for the first time. It consists of two acetylene bonds between adjacent benzene rings. Graphdiyne and its composites thus exhibit ultrahigh intrinsic electrochemical activities. As "star" electrode materials, they have been utilized for various electrochemical applications. With the aim of giving a full screen of graphdiyne electrochemistry, this review starts from the history of graphdiyne materials, followed by their structural and electrochemical features. Recent progress and achievements in the synthesis of graphdiyne materials and their composites are overviewed. Subsequently, various electrochemical applications of graphdiyne materials and their composites are summarized, covering those in the fields of electrochemical energy conversion, electrochemical energy storage, and electrochemical sensing. The perspectives of graphdiyne electrochemistry are also discussed and outlined.

Two-Dimensional Covalent Organic Frameworks as Photocatalysts for Solar Energy Utilization

In the context of energy crisis and global warming, developing clean and sustainable energy is receiving increasing attention. Photocatalytic process including water splitting, CO₂ reduction, coenzyme regeneration, etc., provides an ideal way to utilize renewable solar resources. The photocatalyst plays a central role in photocatalytic processes. Organic porous polymers have recently gained extensive attention in photocatalysis. Covalent organic frameworks (COFs), as one of the organic porous polymers, have the characteristics of high crystallinity, porosity and structural designability that make them perfect platforms for photocatalysis. In this minireview, the recent progresses of 2D COFs as photocatalysts were summarized including our recent work. The synthesis of the diversified structures of the COFs including the different linkages was first introduced. Then, the photocatalytic applications of the 2D COFs including photocatalytic hydrogen evolution, CO₂ conversion, coenzyme regeneration and other traditional organic reaction were then discussed. Finally, conclusions and prospects were provided in the last section. This article is protected by copyright. All rights reserved.

2D graphdiyne: an emerging carbon material

As a new member of carbon allotropes, graphdiyne (GDY) has the characteristics of being one-atom-thick with two-dimensional layers comprising sp and sp² hybridized carbon atoms, and represents a trend in the development of carbon materials. Its unique chemical and electronic structures give GDY many unique and fascinating properties such as rich chemical bonds, highly conjugated and super-large π structures, infinitely distributed pores and high inhomogeneity of charge distribution. GDY has entered a period of rapid development, especially with the significant emergence of fundamental research and applied research achievements over the past five years. As one of the frontiers of chemistry and materials science, graphdiyne was listed in the Top 10 research areas in the 2020 Research Frontiers report and was jointly released in the Top 10 in the world by Clarivate and the Chinese Academy of Sciences. The research results have shown the great potential of GDY in the applications of energy, catalysis, environmental science, electronic devices, detectors, biomedicine and therapy, etc. Scientists are eager to explore and fully reveal the new properties, discover new scientific concepts and phenomena, discover the new conversion modes and mechanisms of GDY in photoelectricity, energy, and catalysis, etc., and build the important scientific value of new conversion devices. This review covers research on the foundation and application of GDY, such as the controlled preparation of new methods of GDY and GDY-based materials, studies on new mechanisms and properties in chemistry and physics, and the foundation and applications in energy, catalysis, photoelectric and devices.

Chemistry, Functionalization, and Applications of Recent Monoelemental Two-Dimensional Materials and Their Heterostructures

The past decades have witnessed a rapid expansion in investigations of two-dimensional (2D) monoelemental materials (Xenes), which are promising materials in various fields, including applications in optoelectronic devices, biomedicine, catalysis, and energy storage. Apart from graphene and phosphorene, recently emerging 2D Xenes, specifically graphdiyne, borophene, arsenene, antimonene, bismuthene, and tellurene, have attracted considerable interest due to their unique optical, electrical, and catalytic properties, endowing them a broader range of intriguing applications. In this review, the structures and properties of these emerging Xenes are summarized based on theoretical and experimental results. The synthetic approaches for their fabrication, mainly bottom-up and top-down, are presented. Surface modification strategies are also shown. The wide applications of these emerging Xenes in nonlinear optical devices, optoelectronics, catalysis, biomedicine, and energy application are further discussed. Finally, this review concludes with an assessment of the current status, a description of existing scientific and application challenges, and a discussion of possible directions to advance this fertile field.

Determination of quinine in tonic water at the miniaturized and polarized liquid-liquid interface

In this work we report an electrochemical approach to quantitative and qualitative analysis of quinine (QN) at the interface between two immiscible electrolyte solutions (ITIES). This was done at the macroscopic (macroITIES) and microscopic (µITIES) systems using ion transfer voltammetry (ITV). The linear response of the peak current vs. increasing concentrations of QN at the µITIES was from 2.50 µM to 29.13 µM and the corresponding calculated limit of detection (LOD) for the current signals originating from QN transfer from the aqueous to the organic phase was equal to 0.49 µM. Additionally, the influence of pH (2-12) of the aqueous phase on the recorded QN signals was investigated. We have found that our method is fully applicable for QN direct determination in non-treated tonic water, as confirmed on three different real samples from three different manufacturers. Finally, a number of validation parameters for the developed method are provided and discussed.

Advances on Graphyne-Family Members for Superior Photocatalytic Behavior

Graphyne (GY) and graphdiyne (GDY) have been employed in photocatalysis since 2012, presenting intriguing electronic and optical properties, such as high electron mobility and intrinsic bandgap due to their high π-conjugated structures. Authors are reporting the enhanced photocatalytic efficiency of these carbon allotropes when combined with different metal oxides or other carbon materials. However, the synthesis of graphyne-family members (GFMs) is still very recent, and not much is known about the true potential of these photocatalytic materials. In this review article, the implications of different synthesis routes on the structural features and photocatalytic properties of these materials are elucidated. The application of GFMs in the nicotinamide adenine dinucleotide (NADH) regeneration, hydrogen and oxygen evolution, and carbon dioxide reduction is discussed, as well as in the degradation of pollutants and bacteria inactivation in water and wastewater treatment.

Large-Area Assembly of Metal-Organic Layered Ultrathin Films at the Liquid/Liquid Interface

Two-dimensional functional metal-organic frameworks and coordination polymers have attracted much attention and have been successfully prepared in solutions and at interfaces through the coordination of ligands to metal ions. However, the preparation of large-area ultrathin ordered films is still a challenge. Here, a modified liquid/liquid interfacial epitaxial growth method has been developed. A planar liquid/liquid interface between a chloroform solution of bipyridine derivatives and pure water was constructed first, and then an aqueous solution of Eu³⁺ or Cu²⁺ ions was added dropwise into the water phase. A layered ultrathin film with the size of several hundreds of square micrometers appeared at the liquid/liquid interface after a certain time. The monitoring results showed that the formation of ultrathin films was a result of continuous epitaxial growth of the adsorbed species due to the synergistic effects of hydrophobic effects of the alkyl chains, coordination bonds between the ligands and metal ions, π-π interactions between the ligands, and the restriction of the interface on the vertical growth. This offers a way to fabricate more large-area thin films of amphiphilic molecules.

Diyne-linked and fully π-conjugated polymetalloporphyrin nanosheets for outstanding heterogeneous catalysis

Two-dimensional, ultrathin, robust, and fully π-conjugated organic nanomaterials are highly desirable for application in various fields due to their unique photoelectric characteristics and great number of exposed active sites. However, such matters combining excellent stability, full π-conjugation and adjustability are rare, which has become a bottleneck for their practical application. Herein, we present a novel kind of diyne-linked polymetalloporphyrin nanosheet featuring permanent porosity and full π-conjugation, which exhibits a high-aspect-ratio, outstanding stability and convenient tailoring for electronic structures. Importantly, the novel nanosheets with monodisperse nickel atoms were found to be outstanding heterogeneous catalyst with unprecedented catalytic activity and selectivity for 4-nitrophenol reduction to 4-aminophenol under mild conditions. The findings recommend that diyne-linked polymetalloporphyrin nanosheets may offer new platforms for the conversion of photoelectricity and energy in the future.

C-C Coupling Reactions for the Synthesis of Two-Dimensional Conjugated Polymers

Extension of conjugated polymers from 1D to 2D can not only significantly enhance the dissociation of charge and excitons, but also induce other advantages, such as high in-plane mechanical strength, large specific surface area and porosity, and more active centers. 2D conjugated polymers can be divided into C-C bonded 2D polymers based on C-C coupling reactions, and heteroatomic bonded 2D polymers based on reversible heteroatom coupling reactions. C-C bonded 2D polymers are generally more stable than heteroatomic bonded 2D polymers as the latter bonds are easily hydrolyzed. This Review mainly summarizes C-C coupling reactions that are suitable for synthesizing 2D conjugated polymers, and the properties of these 2D conjugated polymers are also introduced.

Graphitic Carbon Nitride Films: Emerging Paradigm for Versatile Applications

Graphitic carbon nitride (g-C₃N₄) is a well-known two-dimensional conjugated polymer semiconductor that has been broadly applied in photocatalysis-related fields. However, further developments of g-C₃N₄, especially in device applications, have been constrained by the inherent limitations of its insoluble nature and particulate properties. Recent breakthroughs in fabrication methods of g-C₃N₄ films have led to innovative and inspiring applications in many fields. In this review, we first summarize the fabrication of continuous and thin films, either supported on substrates or as free-standing membranes. Then, the novel properties and application of g-C₃N₄ films are the focus of the current review. Finally, some underlying challenges and the future developments of g-C₃N₄ films are tentatively discussed. This review is expected to provide a comprehensive and timely summary of g-C₃N₄ film research to the wide audience in the field of conjugated polymer semiconductor-based materials.

Nanocarbon-Enhanced 2D Photoelectrodes: A New Paradigm in Photoelectrochemical Water Splitting

Solar-driven photoelectrochemical (PEC) water splitting systems are highly promising for converting solar energy into clean and sustainable chemical energy. In such PEC systems, an integrated photoelectrode incorporates a light harvester for absorbing solar energy, an interlayer for transporting photogenerated charge carriers, and a co-catalyst for triggering redox reactions. Thus, understanding the correlations between the intrinsic structural properties and functions of the photoelectrodes is crucial. Here we critically examine various 2D layered photoanodes/photocathodes, including graphitic carbon nitrides, transition metal dichalcogenides, layered double hydroxides, layered bismuth oxyhalide nanosheets, and MXenes, combined with advanced nanocarbons (carbon dots, carbon nanotubes, graphene, and graphdiyne) as co-catalysts to assemble integrated photoelectrodes for oxygen evolution/hydrogen evolution reactions. The fundamental principles of PEC water splitting and physicochemical properties of photoelectrodes and the associated catalytic reactions are analyzed. Elaborate strategies for the assembly of 2D photoelectrodes with nanocarbons to enhance the PEC performances are introduced. The mechanisms of interplay of 2D photoelectrodes and nanocarbon co-catalysts are further discussed. The challenges and opportunities in the field are identified to guide future research for maximizing the conversion efficiency of PEC water splitting.

Graphdiyne-Supported Atomic Catalysts: Synthesis and Applications

Graphdiyne (GDY) has been ideal candidate support for atomic catalysts (ACs) due to its unique conjugated two-dimensional (2D) structure comprising both sp- and sp² -hybrid carbon atoms. ACs/GDY can display excellent catalytic ability and high selectivity, emerging as a cutting-edge research area in the past few years. Recently, a growing body of work has been done in ACs/GDY, ranging from screening appropriate combinations theoretically, continuous improvement to prepare few-layered GDY to meet the critical challenge in this area, and successfully fabricating ACs/GDY in facile way. This Minireview briefly introduces recent advanced progress in this field, including the synthetic method for both thin GDY film and ACs/GDY, as well as theoretical analysis of different ACs/GDY systems, characterization, and applications. In the end, the challenges and further opportunities of ACs/GDY are summarized and proposed. It is hoped that this article brings new insights into the current study of ACs/GDY and promotes better development in this area.

High Quality Pyrazinoquinoxaline-Based Graphdiyne for Efficient Gradient Storage of Lithium Ions

N-doping of graphdiyne with atomic precision is very important for the study of heteroatom doping effect and the structure-properties relationships of graphdiyne. Here we report the bottom-up synthesis and characterizations of high-quality pyrazinoquinoxaline-based graphdiyne (PQ-GDY) film. First-principle studies of the layered structure were performed to examine the stacking mode, lithium binding affinity, and bulk lithium storage capacity. Three-stage insertion of 14 lithium atoms with binding affinities in the order of pyrazine nitrogen > diyne carbon > central aromatic ring were confirmed by both lithium-ion half-cell measurements and DFT calculations. More than half of the lithium atoms preferentially bind to pyrazine nitrogen, and a reversible capacity of 570.0 mA h g^-1 at a current density of 200 mA g^-1 after 800 cycles was achieved. Such a high capacity utilization rate of 97.2% provides a good case study of N-doped GDY with atomic precision.

3D structured materials and devices for artificial photosynthesis

Artificial photosynthesis is an effective way to convert solar energy into fuels, which is of great significance to energy production and reduction of atmospheric CO₂ content. In recent years, 3D structured artificial photosynthetic system has made great progress as an effective design strategy. This review first highlights several typical mechanisms for improved artificial photosynthesis with 3D structures: improved light harvesting, mass transfer and charge separation. Then, we summarize typical examples of 3D structured artificial photosynthetic systems, including bioinspired structures, photonic crystals (PC), designed photonic structures (PC coupling structure, plasmon resonance structure, optical resonance structure, metamaterials), 3D-printed systems, nanowire integrated systems and hierarchical 3D structures. Finally, we discuss the problems and challenges to the application and development of 3D artificial photosynthetic system and the possible trends of future development. We hope this review can inspire more progress in the field of artificial photosynthesis.

Interfacial Synthesis of a Monolayered Fluorescent Two-Dimensional Polymer through Dynamic Imine Chemistry

A fluorescent monolayered two-dimensional polymer (2DP) containing both tetraphenylethylene (TPE) and imine linkages is synthesized at air-water interface using the Langmuir-Blodgett method. We designed TPE-based monomers with long distances between the TPE and the imine linkages to avoid the charge transfer and therefore keep the fluorescence. A monolayered 2DP provided with more than 104 μm2 in domain size and around 0.8 nm thickness was obtained through a successive Schiff base reaction at air-water interface. The nanostructures and fluorescent property of 2DP films were characterized by optical microscopy, SEM, TEM, AFM and fluorescence spectrum. Most importantly, the tip-enhanced Raman spectroscopy (TERS) was utilized here to confirm the success of the polycondensation of monolayered 2DP.

Interfacial synthesis of crystalline two-dimensional cyano-graphdiyne

A well-defined crystalline cyano-functionalized graphdiyne (CN-GDY) is synthesized at a liquid/liquid interface through alkyne–alkyne coupling reactions.

Facile assembly of a graphitic carbon nitride film at an air/water interface for photoelectrochemical NADH regeneration

A graphitic carbon nitride film electrode could be assembled at an air/water interface from nanosheets which exhibits improved photoelectrochemical coenzyme regeneration by further coupling with graphene during the interfacial self-assembly.

Sulfur-rich Graphdiyne-Containing Electrochemical Active Tetrathiafulvalene for Highly Efficient Lithium Storage Application

A sulfur-rich graphdiyne (TTF-GDY) material containing electrochemically active unit of tetrathiafulvalene was successfully synthesized at the liquid/liquid interface under mild conditions. The extended two-dimensional (2D) π-conjugated framework contains large in-plane cavities to accommodate defined sulfur elements and precise sulfur content. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) characterizations demonstrated that the TTF-GDY adopted the layered structures. X-ray photoelectron spectroscopy (XPS), Raman spectrum, selected area electron diffraction (SAED), crystal modeling, and molecular-mechanics-based calculation further confirmed the proposed framework structure and the expected chemical compositions. Considering the unique structure and sulfur-rich characteristic, we then applied this material as an electrode in lithium battery applications. Due to the unique 2D framework structure, the TTF-GDY exhibited a high specific capacity of 837.6 mAh/g, particularly having a robust long-term stability under the high current density. These results demonstrated that such a sulfur-rich TTF-GDY, as a novel electrochemical material would have great application potential in energy fields.

Graphdiyne doped with sp-hybridized nitrogen atoms at acetylenic sites as potential metal-free electrocatalysts for oxygen reduction reaction

Exploring metal-free electrocatalysts with high efficiency and lower cost for oxygen reduction reaction (ORR) is necessary to realize the commercialization of fuel cells. In this paper, the ORR mechanisms on nitrogen-doped graphdiyne (GDY) are investigated using the first principles calculations. It is found that the GDY doped with sp-hybridized N at acetylenic sites can activate molecular oxygen (O₂). The kinetically most favorable reaction pathway is O₂  →  OOH  →  O  +  H₂O  →  OH  →  H₂O, which is an efficient four-electron ORR process. The first reaction step O₂  →  OOH is the rate determining step (RDS), and the energy barrier is 0.61 eV. The energy barrier of RDS is smaller than that of pure Pt (0.80 eV). Therefore, these results illustrate that sp-hybridized N-doped GDY is a promising carbon-based metal-free ORR catalyst.

The Accelerating World of Graphdiynes

Graphdiyne (GDY), a 2D allotrope of graphene, is first synthesized in 2010 and has attracted attention as a new low-dimensional carbon material. This work surveys the literature on GDYs. The history of GDYs is summarized, including their relationship with 2D graphyne carbons and yearly publication trends. GDY is a molecule-based nanosheet woven from a molecular monomer, hexaethynylbenzene; thus, it is synthesized by bottom-up approaches, which allow rich variation via monomer design. The GDY family and the synthetic procedures are also described. Highly developed π-conjugated electronic structures are common important features in GDY and graphene; however, the coexistence of sp and sp² carbons differentiates GDY from graphene. This difference gives rise to unique physical properties, such as high conductivity and large carrier mobility. Next, the theoretical and experimental studies of these properties are described in detail. A wide variety of applications are proposed for GDYs, including electrocatalysts and energy devices, which exploit the carbon-rich nature, porous framework, and expanded π-electron system of these compounds. Finally, potential uses are discussed.

Catalytic recycling of NAD(P)H

A large number of industrially relevant enzymes depend upon dihydronicotinamide adenine dinucleotide (NADH) and dihydronicotinamide adenine dinucleotide phosphate (NADPH) cofactors, which are too expensive to be added in stoichiometric amounts. Existing NAD(P)H-recycling systems suffer from low activity, or the generation of side products. This review focuses on NAD(P)H cofactor regeneration catalyzed by transition metal complexes such as rhodium, ruthenium and iridium complexes using cheap reducing agents such as hydrogen (H₂) and ethanol, which have attracted increasing attention as sustainable energy carriers. The catalytic mechanisms for the regioselective reduction of NAD(P)⁺ are discussed with emphasis on identification of catalytically active intermediates such as transition metal hydride complexes. Applications of NAD(P)H-recycling systems to develop artificial photosynthesis are also discussed.

Graphdiyne: synthesis, properties, and applications

Graphdiyne (GDY), a new two-dimensional (2D) carbon allotrope, has been receiving increased attention. Its unique sp-sp2 carbon atoms, uniform pores, and highly π-conjugated structure provide promising potential in practical applications, such as gas separation, catalysis, water remediation, humidity sensor, and energy-related fields. In the recent years, considerable efforts have been expended toward the development of well-defined GDY. However, GDY materials still face numerous challenges, including the need for a more thorough understanding of the growth mechanism, strategies for synthesizing one- or few-layer single-crystalline GDY films, characterization of basic physicochemical properties, and achievement of promising applications. This review aims at providing a comprehensive update on the synthesis of GDY and GDY-based materials, as well as their properties, including structural, electronic, mechanical, and spectral properties, and their applications in nanotechnology.

A facile liquid/liquid interface method to synthesize graphyne analogs

A novel interfacial synthetic approach for preparing varieties of gauze-like graphyne analogs.

Graphdiyne: Recent Achievements in Photo- and Electrochemical Conversion

As a rising star of carbon allotropes, graphynes (GYs) merely consist of sp- and sp2-hybridized carbon atoms, which endow them a large conjugated network and expanded 2D porous structure. With unique topological structure, GYs display unusual semiconducting properties, especially in the aspects of charge mobility and electron transport. Among the members of the GY family, only graphdiyne (GD) can be successfully synthesized in large quantities. The advanced properties of GD make it promising in various applications. Here, the recent progress in the synthesis of GD and GD-based composites is reviewed as well as their applications in photorelated and electrocatalytic applications. It is hoped that this Review will promote the development and applications of carbon chemistry.