Architecture of β-Graphdiyne-Containing Thin Film Using Modified Glaser-Hay Coupling Reaction for Enhanced Photocatalytic Property of TiO2

Unlocking Diverse π-Bond Enrichment Frameworks by the Synthesis and Conversion of Boronated Phenyldiethynylethylenes

The π-bond enrichment frameworks not only serve as a crucial building block in organic synthesis but also assume a pivotal role in the fields of materials science, biomedicine, photochemistry, and other related disciplines owing to their distinctive structural characteristics. The incorporation of various substituents into the C═C double bonds of tetrasubstituted alkenes is currently a highly significant research area. However, the synthesis of tetrasubstituted alkenes with diverse substituents on double bonds poses a significant challenge in achieving stereoselectivity. Here, we reported an efficient and convergent route of Cu-catalyzed borylalkynylation of both symmetrical and unsymmetrical 1,3-diynes, B2pin2, and acetylene bromide to the construction of boronated phenyldiethynylethylene (BPDEE) derivatives with excellent chemo-, stereo-, and regioselectivities. BPDEE derivatives could transform into novel tetrasubstituted organic π-conjugated gem-diphenyldiethynylethylene (DPDEE), vinylphenyldiethynylethylene (VPDEE), and phenyltriethynylethylene (PTEE) derivatives by a stepwise process, which provides a flexible platform for the synthesis of complex π-bond enrichment frameworks that were difficult to synthesize by previous methods. The initial optical characterization revealed that the synthesized molecules exhibited aggregation-induced emission (AIE) properties, which further establishes the groundwork for future applications and enriches and advances the field of functional π-conjugated frameworks research.

A nitrogen-rich graphdiyne containing hexaazatrinaphthylene for high-performance lithium-ion batteries

A nitrogen-rich graphdiyne (HATN-GDY) material containing electrochemical active hexaazatrinaphthylene units was successfully prepared. HATN-GDY exhibits a superior specific capacity of 2139 mA h g-1 and firm long-term stability due to the unique 2D π-conjugated structure and the large in-plane N-cavities.

Triple-Mode Sensor Coupled by Photoelectrochemical, Electrochromic, and Spectral Signals for Sensitive Visualized Detection of Nonylphenol

Conventional photoelectrochemical (PEC) biosensors suffer from the difficulty of visualizing rapid detection and limited accuracy due to a single-signal output. Here, we develop a PEC, electrochromic (EC), and spectral (ST) triple-mode platform for the sensitive visualized detection of nonylphenol (NP). First, the reasonably stepped Fermi energy level arrangement between the defective TiO2 anode and MoO3 cathode enables a remarkable photocurrent response (Mode 1). Then, MoO3 itself is a widely used EC candidate, which can react with free Li-ions to form a LixMoO3 intermediate, and its color will change from white to blue accordingly (Mode 2). More importantly, MoO3 is also a Li-ion host and the potential of LixMoO3 depends on the inserted Li-ion quantity deduced by spectral analysis on residual Li-ions in the electrolyte (Mode 3). The EC signal endows fast visual detection, and triple-mode cross-validation improves reliability and accuracy. As a result, this PEC-EC-ST triple-mode molecularly imprinted sensor has a wide linear range (1-5000 μg L-1), a low detection limit (0.18 μg L-1), selectivity, stability, reproducibility, and actual sample detection capability. This innovative multimode platform not only improves detection reliability but also broadens applications of electrochromic/energy storage materials in biosensors.

State, synthesis, perspective applications, and challenges of Graphdiyne and its analogues: A review of recent research

Carbon materials technology provides the possibility of synthesizing low-cost, outstanding performance replacements to noble-metal catalysts for long-term use. Graphdiyne (GDY) is a carbon allotrope with an extremely thin atomic thickness. It consists of carbon elements, that are hybridized with both sp. and sp2, resulting in a multilayered two-dimensional (2D) configuration. Several functional models suggest, that GDY contains spontaneously existing band structure with Dirac poles. This is due to the non-uniform interaction among carbon atoms, which results from various fusions and overlapping of the 2pz subshell. Unlike other carbon allotropes, GDY has Dirac cone arrangements, that in turn give it inimitable physiochemical characteristics. These properties include an adjustable intrinsic energy gap, high speeds charging transport modulation efficiency, and exceptional conductance. Many scientists are interested in such novel, linear, stacked materials, including GDY. As a result, organized synthesis of GDY has been pursued, making it one of the first synthesized GDY materials. There are several methods to manipulate the band structure of GDY, including applying stresses, introducing boron/nitrogen loading, utilizing nanowires, and hydrogenations. The flexibility of GDY can be effectively demonstrated through the formation of nano walls, nanostructures, nanotube patterns, nanorods, or structured striped clusters. GDY, being a carbon material, has a wide range of applications owing to its remarkable structural and electrical characteristics. According to subsequent research, the GDY can be utilized in numerous energy generation processes, such as electrochemical water splitting (ECWS), photoelectrochemical water splitting (PEC WS), nitrogen reduction reaction (NRR), overall water splitting (OWS), oxygen reduction reaction (ORR), energy storage materials, lithium-Ion batteries (LiBs) and solar cell applications. These studies suggested that the use of GDY holds significant potential for the development and implementation of efficient, multimodal, and intelligent catalysts with realistic applications. However, the limitation of GDY and GDY-based composites for forthcoming studies are similarly acknowledged. The objective of these studies is to deliver a comprehensive knowledge of GDY and inspire further advancement and utilization of these unique carbon materials.

Prospects of 2D graphdiynes and their applications in desalination and wastewater remediation

Water is an indispensable part of human life that affects health and food intake. Water pollution caused by rapid industrialization, agriculture, and other human activities affects humanity. Therefore, researchers are prudent and cautious regarding the use of novel materials and technologies for wastewater remediation. Graphdiyne (GDY), an emerging 2D nanomaterial, shows promise in this direction. Graphdiyne has a highly symmetrical π-conjugated structure consisting of uniformly distributed pores; hence, it is favorable for applications such as oil-water separation and organic-pollutant removal. The acetylenic linkage in GDY can strongly interact with metal ions, rendering GDY applicable to heavy-metal adsorption. In addition, GDY membranes that exhibit 100% salt rejection at certain pressures are potential candidates for wastewater treatment and water reuse via desalination. This review provides deep insights into the structure, properties, and synthesis methods of GDY, owing to which it is a unique, promising material. In the latter half of the article, various applications of GDY in desalination and wastewater treatment have been detailed. Finally, the prospects of these materials have been discussed succinctly.

Boosting charge separation in graphdiyne quantum dots/hollow tubular carbon nitride heterojunction for water pollutant degradation

Non-desirable solar energy absorption and poor charge transfer efficiency are two problems that limit the peroxymonosulfate (PMS) photocatalytic techniques. Herein, a metal-free boron-doped graphdiyne quantum dot (BGDs) modified hollow tubular g-C₃N₄ photocatalyst (BGD/TCN) was synthesized to activate PMS and achieved effective space separation of carriers for degradation of bisphenol A. With 0.5 mM PMS, the degradation rate of bisphenol A (20 ppm) was 0.0634 min^-1, 3.7-fold higher than that of TCN itself. The roles of BGDs in the distribution of electrons and photocatalytic property were well identified by experiments and density functional theory (DFT) calculations. The possible degradation intermediate products of bisphenol A were monitored by mass spectrometer and demonstrated to be nontoxic using ecological structure activity relationship modeling (ECOSAR). Finally, this newly-designed material was successfully applied in actual water bodies, which further renders its promising prospect for actual water remediation.

Graphynes and Graphdiynes for Energy Storage and Catalytic Utilization: Theoretical Insights into Recent Advances

Carbon allotropes have contributed to all aspects of people's lives throughout human history. As emerging carbon-based low-dimensional materials, graphyne family members (GYF), represented by graphdiyne, have a wide range potential applications due to their superior physical and chemical properties. In particular, graphdiyne (GDY), as the leader of the graphyne family, has been practically applied to various research fields since it was first successfully synthesized. GYF have a large surface area, both sp and sp² hybridization, and a certain band gap, which was considered to originate from the overlap of carbon 2p_z orbitals and the inhomogeneous π-bonds of carbon atoms in different hybridization forms. These properties mean GYF-based materials still have many potential applications to be developed, especially in energy storage and catalytic utilization. Since most of the GYF have yet to be synthesized and applications of successfully synthesized GYF have not been developed for a long time, theoretical results in various application fields should be shared to experimentalists to attract more intentions. In this Review, we summarized and discussed the synthesis, structural properties, and applications of GYF-based materials from the theoretical insights, hoping to provide different viewpoints and comments.

Facile Synthesis of Hydrogen-Substituted Graphdiyne Powder via Dehalogenative Homocoupling Reaction

Graphdiyne and its analogs are a series of artificial two-dimensional nanomaterials with sp hybridized carbon atoms, which can be viewed as the insertion of two acetylenic units between adjacent aromatic rings, evenly expanded on a flat surface. Although developed in recent years, new synthetic strategies for graphdiyne analogs are still required. This work proposed a new method to prepare hydrogen-substituted graphdiyne powder via a dehalogenative homocoupling reaction. The polymerization was unanticipated while the initial goal was to synthesize a γ-graphyne analog via Sonogashira cross-coupling reaction. Compared with previous synthetic strategies, the reaction time was conspicuously shortened and the Pd catalyst was inessential. The powder obtained exhibited a porous structure and high electrocatalytic activity in the hydrogen/oxygen evolution reaction, which has the potential for application in electrochemical catalysis. The reported methodology provides an efficient synthetic strategy for large-scale preparation.

Curved π-Conjugated Helical Carbon Frameworks: Syntheses, Structural Analyses, and Properties

Two enantiomers with helical carbon frameworks (M-HCFa and P-HCFa) and their conformational isomers (M-HCFb and P-HCFb) have been synthesized and characterized. The single-crystal analysis revealed the novel structures in which three propeller blades spiro-fused on two central benzene rings. The optical properties were further investigated, and stable bipolar electrochemiluminescence emissions were discovered for the first time existing in helical carbon frameworks, which provide new insights into the future development of high-performance molecular luminescent devices.

Vibrational properties of graphdiynes as 2D carbon materials beyond graphene

Two-dimensional (2D) hybrid sp–sp² carbon systems are an appealing subject for science and technology. For these materials, topology and structure significantly affect electronic and vibrational properties. We investigate here by periodic density-functional theory (DFT) calculations the Raman and IR spectra of 2D carbon crystals belonging to the family of graphdiynes (GDYs) and having different structures and topologies. By joining DFT calculations with symmetry analysis, we assign the IR and Raman modes in the spectra of all the investigated systems. On this basis, we discuss how the modulation of the Raman and IR active bands depends on the different interactions between sp and sp² domains. The symmetry-based classification allows identifying the marker bands sensitive to the different peculiar topologies. These results show the effectiveness of vibrational spectroscopy for the characterization of new nanostructures, deepening the knowledge of the subtle interactions that take place in these 2D materials.

Raman and IR spectra investigation of 2D carbon crystals belonging to the family of graphdiynes (GDYs) and having different structures is performed in this paper, focusing on how these spectra are affected by different topological features.

Graphdiyne/Graphene/Graphdiyne Sandwiched Carbonaceous Anode for Potassium-Ion Batteries

Graphdiyne (GDY) has been considered as an appealing anode candidate for K-ion storage since its triangular pore channel, alkyne-rich structure, and large interlayer spacing would endow it with abundant active sites and ideal diffusion paths for K-ions. Nevertheless, the low surface area and disordered structure of bulk GDY typically lead to unsatisfied K storage performance. Herein, we have designed a GDY/graphene/GDY (GDY/Gr/GDY) sandwiched architecture affording a high surface area and fine quality throughout a van der Waals epitaxy strategy. As tested in a half-cell configuration, the GDY/Gr/GDY electrode exhibits better capacity output, rate capability, and cyclic stability as compared to the bare GDY counterpart. In situ electrochemical impedance spectroscopy/Raman spectroscopy/transmission electron microscopy are further applied to probe the K-ion storage feature and disclose the favorable reversibility of GDY/Gr/GDY electrode during repeated potassiation/depotassiation. A full-cell device comprising a GDY/Gr/GDY anode and a potassium Prussian blue cathode enables a high cycling stability, demonstrative of the promising potential of the GDY/Gr/GDY anode for K-ion batteries.

Substituted Tetraethynylethylene-Tetravinylethylene Hybrids

A general synthetic approach to molecular structures that are hybrids of tetraethynylethylene (TEE) and tetravinylethylene (TVE) is reported. The synthesis permits the controlled preparation of many previously inaccessible structures, including examples with different substituents on each of the four branching arms. Most substituted TVE-TEE hybrids are found to be significantly more robust compounds than their unsubstituted counterparts, enhancing the prospects of their deployment in conducting materials and devices. Their participation in pericyclic reaction cascades, leading to sp³-rich polycycles, is demonstrated. The utilization of TEE-TVE hybrids as building blocks for larger acyclic, through/cross-conjugated hydrocarbon frameworks is also established. Aryl-substituted TEEs, TVEs, and their hybrids are fluorescent, with some exhibiting aggregation-induced emission enhancement. The structural requirements are defined and explained, setting the scene for applications as fluorescent probes and organic light-emitting diodes.

Interface engineering: Synergism between S-scheme heterojunctions and Mo-O bonds for promote photocatalytic hydrogen evolution

Simple high-temperature calcination and hydrothermal methods were followed to synthesize CeO₂ and Mo-S, respectively. The efficient photocatalytic hydrogen evolution activity exhibited by the composite catalysts can be attributed to the edge active sites in Mo-S. The Mo-O bonds formed between CeO₂ and Mo-S could further accelerate the processes of separation and migration of electrons between the catalyst interfaces. The hybrid catalyst 10%-CeO₂/Mo-S exhibiting the best hydrogen generation ability (4.3 mmol h^-1g^-1) was obtained by optimizing the content of CeO₂ in CeO₂/Mo-S. Analysis of the PL spectral profile and photocurrent response recorded for the system revealed that 10%-COMS exhibited excellent photogenerated carrier separation ability. Analysis of the LSV and EIS curves revealed that 10%-COMS exhibited the optimal hydrogen production potential. The charge migration resistance provided by the systems was lower than the charge migration resistance provided by CeO₂ and Mo-S. The synergism between the S-scheme heterojunctions and the Mo-O bonds helped accelerate the separation and migration of photo-induced carriers at the catalyst interfaces. The introduction of covalent bonds in the S-scheme heterojunctions and the results presented herein can potentially help develop a new method to realize photocatalytic hydrogen evolution.

Interconnected MoS2 on 2D Graphdiyne for Reversible Sodium Storage

In this study, graphdiyne (GDY) was first reported as a substrate material for sodium-ion batteries (SIBs). The creative hybridization of GDY and molybdenum disulfide (MoS₂) endows the composite with unique heterostructural and morphological advantages that boost the charge transport rate and enhance the battery discharge properties. Electrochemical results indicated that the MoS₂@GDY anode displays a considerable discharge capacity of up to 328 mAh g^-1 at 1000 mA g^-1. A capacity retention of 93% even at testing current back to 200 mA g^-1 suggests superior rate characteristics. An outstanding stable cyclic performance of 217 mAh g^-1 is obtained at a high testing density. The attractive results not only demonstrate that GDY could be used not only as an effective conductive substrate to prevent the host material from agglomerating in the electrochemical process but also provide a novel design for fabricating efficient electrode materials for future energy-storage systems.

New Two-Dimensional Wide Band Gap Hydrocarbon Insulator by Hydrogenation of a Biphenylene Sheet

Based on first-principles calculations, the ground state configuration (Cmma-CH) of a hydrogenated biphenylene sheet ( Science 2021, 372, 852) is carefully identified from hundreds of possible candidates generated by RG² code ( Phys. Rev. B. 2018, 97, 014104). Cmma-CH contains four inequivalent benzene molecules in its crystalline cell due to its Cmma symmetry. Hydrogen atoms bond to carbon atoms in each benzene with a boat-like (DDUDDU) up/down sequence and reversed boat-1 (UUDUUD) sequence in adjacent benzene rings. Cmma-CH is energetically less stable than the proposed allotropes of hydrogenated graphene, but the formation energy for hydrogenating a biphenylene sheet is remarkably lower than that for hydrogenating graphene to graphane. Our results of mechanical and dynamical stability also confirm that Cmma-CH is a stable 2D hydrocarbon, which is expected to be realized experimentally. Especially, biphenylene undergoes a transition from normal metal to a wide band gap insulator (4.645 eV) by hydrogenation to Cmma-CH, which has potential applications in nanodevices at elevated temperatures and high voltages.

Tunable topologically nontrivial states in newly discovered graphyne allotropes: from Dirac nodal grid to Dirac nodal loop

By means of quotient-graph associated crystal prediction method, a new graphyne allotrope with unique Dirac nodal grid state is reported in this work. It is named as 191-E24Y24-1 according to its hexagonal lattice (with P6/mmm symmetry, No. 191) containing 24 sp²-hybridized carbon atoms and 24 sp-hybridized ones. The first-principles results show that the total energy of 191-E24Y24-1 is more favorable than that of recent synthesizedβ-graphdiyne and carbon ene-yne. It is also demonstrated to be dynamically, thermally, and mechanically stable. Interestingly, the 191-E24Y24-1 harbors intrinsic semimetal features showing intriguing hexagonal Dirac nodal grid state in the reciprocal space. Such unique electronic state is stable against small external tensile strains, and it is tunable under compression strains which will transform to new triangle Dirac nodal grid state. Moreover, a new metastable graphyne allotrope named 191-E12Y36-4 with Dirac nodal loop state is also observed in the process of stretching 191-E24Y24-1 with large tensile strains. The results presented in this work reveal two novel graphyne allotropes with exotic electronic properties. These discoveries are not only physical interesting, but also provide potential material candidates for carbon-based high performance electronic nanodevices.

Developments in Synthesis and Potential Electronic and Magnetic Applications of Pristine and Doped Graphynes

Doping and its consequences on the electronic features, optoelectronic features, and magnetism of graphynes (GYs) are reviewed in this work. First, synthetic strategies that consider numerous chemically and dimensionally different structures are discussed. Simultaneous or subsequent doping with heteroatoms, controlling dimensions, applying strain, and applying external electric fields can serve as effective ways to modulate the band structure of these new sp2/sp allotropes of carbon. The fundamental band gap is crucially dependent on morphology, with low dimensional GYs displaying a broader band gap than their bulk counterparts. Accurately chosen precursors and synthesis conditions ensure complete control of the morphological, electronic, and physicochemical properties of resulting GY sheets as well as the distribution of dopants deposited on GY surfaces. The uniform and quantitative inclusion of non-metallic (B, Cl, N, O, or P) and metallic (Fe, Co, or Ni) elements into graphyne derivatives were theoretically and experimentally studied, which improved their electronic and magnetic properties as row systems or in heterojunction. The effect of heteroatoms associated with metallic impurities on the magnetic properties of GYs was investigated. Finally, the flexibility of doped GYs' electronic and magnetic features recommends them for new electronic and optoelectronic applications.

Synthesis of hydrogen-substituted graphdiynes via dehalogenative homocoupling reactions

A new method is introduced to prepare hydrogen-substituted graphdiynes (HsGDYs) via the dehalogenative homocoupling of terminal alkynyl bromides. Compared with previous synthetic strategies, the reaction conditions are moderate and the time is shortened. HsGDYs exhibit porous structures and hydrogen/oxygen evolution reaction (HER/OER) catalytic activity, endowing applications in electrochemical catalysis.

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.

Ultrahigh hydrogen storage capacity of holey graphyne

Holey graphyne (HGY), a novel two-dimensional (2D) single-crystalline carbon allotrope, was recently synthesized by Castro-Stephens coupling reaction. The naturally existing uniform periodic holes in the 2D carbon-carbon network demonstrate its promising potential in energy storage. Herein, we conduct density functional theory (DFT) calculation and ab initio molecular dynamics simulations (AIMD) to predict the H storage properties of a single-layer HGY sheet modified by Li metal atoms. The DFT calculations demonstrate that Li atoms can bind strongly to the HGY sheet without forming clusters, and each Li atom can anchor four H2 molecules with an average adsorption energy of about -0.22 eV/H2. The largest H storage capacity of the doped HGY sheet can reach as high as 12.8 wt%, showing that the Li/HGY complex is an ideal H storage material at ambient conditions. In addition, we investigate the polarization mechanism of the storage media and find that the polarization originates from the electric field induced by both the ionic Li atoms and the weak polarized H2 molecules. Finally, the desorption mechanism of the adsorbed H2 molecules is thoroughly investigated using a kinetic AIMD method.

Newly discovered graphyne allotrope with rare and robust Dirac node loop

Two-dimensional (2D) carbon allotropes with topologically nontrivial states are drawing considerable attention owing to their unique physical properties and great potential applications in the next generation of micro-nano devices. In contrast to the numerous Dirac points predicted in 2D carbon allotropes, systems featuring Dirac nodal lines (loops) are still quite rare. Here, by means of first-principles calculation, we report our newly discovered carbon monolayer 123-E8Y24-1 with robust Dirac nodal line states, which possesses a tetragonal lattice with P4/mmm symmetry and contains 8 sp² carbon atoms (graphene: E8) and 24 sp carbon atoms (grapheyne: Y24) in the crystalline cell. This 2D material is as energetically stable as the recently experimentally synthesized β-graphdiyne, and it is further predicted to be dynamically, mechanically, and also thermodynamically stable. Owing to its intrinsic geometric characteristics, 123-E8Y24-1 also exhibits obvious Young's modulus anisotropy, with a sizable ratio between the maximum and minimum value of up to 5.8. Remarkably, 123-E8Y24-1 presents a semimetal nature and possesses Dirac nodal line states in the electronic band structure, and such behavior could be kept well under external strain between -10.0% and 8.0%. The electronic properties of 123-E8Y24-1 can be carefully confirmed by constructing a tight-binding (TB) model. The findings presented in this paper reveal a novel 2D Dirac nodal loop carbon sheet, providing a new candidate for carbon-based high-speed electronic devices.

Synthesis of Wafer-Scale Monolayer Pyrenyl Graphdiyne on Ultrathin Hexagonal Boron Nitride for Multibit Optoelectronic Memory

Graphdiyne is a new two-dimensional carbon allotrope with many attractive properties and has been widely used in various applications. However, the synthesis of large-area, high-quality, and ultrathin (especially monolayer) graphdiyne and its analogues remains a challenge, hindering its application in optoelectronic devices. Here, a wafer-scale monolayer pyrenyl graphdiyne (Pyr-GDY) film is obtained on hexagonal boron nitride (hBN) via a van der Waals epitaxial strategy, and top-floating-gated multibit nonvolatile optoelectronic memory based on Pyr-GDY/hBN/graphene is constructed, using Pyr-GDY as a photoresponsive top-floating gate. Benefiting from the excellent charge trapping capability and strong absorption of the graphdiyne film, as well as the top-floating-gated structure and the ultrathin hBN film used in the device, the optoelectronic memory exhibits high storage performance and robust reliability. A huge difference in the current between the programmed and erased states (>26 μA μm^-1 at V_ds = 0.1 V) and a prolonged retention time (>10⁵ s) enable the device to achieve multibit storage, for which eight and nine distinct storage levels (3-bit) are obtained by applying periodic gate voltages and optical pulses in the programming and erasing processes, respectively. This work provides an important step toward realizing versatile graphdiyne-based optoelectronic devices in the future.

Structural and electronic properties of α-, β-, γ-, and 6,6,18-graphdiyne sheets and nanotubes

α-, β-, γ- and 6,6,18-graphdiyne (GDYs) sheets, as well as the corresponding nanotubes (GDYNTs) are investigated systematically by using the self-consistent-field crystal orbital method. The calculations show that the GDYs and GDYNTs with different structures have different electronic properties. The α-GDY sheet is a conductor, while 2D β-, γ- and 6,6,18-GDYs are semiconductors. The carrier mobilities of β- and γ-GDY sheets in different directions are almost the same, indicating the isotropic transport characteristics. In addition, the electron mobility is in the order of 106 cm2 V-1 s-1 and it is two orders of magnitude larger than the hole mobility of 2D γ-GDY. However, α- and 6,6,18-GDY sheets have anisotropic mobilities, which are different along different directions. For the 1D tubes, the order of stability is γ-GDYNTs > 6,6,18-GDYNTs > β-GDYNTs > α-GDYNTs and is independent of the tube chirality and size. β- and γ-GDYNTs as well as zigzag α- and 6,6,18-GDYNTs are semiconductors with direct bandgaps, while armchair α-GDYNTs are metals, and armchair 6,6,18-GDYNTs change from semiconductors to metals with increasing tube size. The armchair β- and γ-GDYNTs are more favourable to transport holes, while the corresponding zigzag tubes prefer to transport electrons.

Graphyne-anchored single Fe atoms as efficient CO oxidation catalysts as predicted by DFT calculations

By performing first-principles calculations, CO oxidation catalyzed by Fe-embedded defective α-graphyne was systematically investigated. It was found that Fe atoms were strongly anchored at the sp-C vacancy site of α-graphyne with a large binding energy of -5.28 eV and effectively adsorbed and activated O2 molecules. Then, we systematically compared CO oxidation by activated O2via Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms. The calculated potential energy surfaces show that the Fe-doped α-graphyne can efficiently oxidize CO via the ER mechanism, in which the threshold of the rate determining step is 0.77 eV. Furthermore, Fe doping shows little effect on the diffusivities of CO, O2, and CO2, which can further enhance its catalytic performance.

Synthesis and Properties of 2,3-Diethynyl-1,3-Butadienes

The first general preparative access to compounds of the 2,3-diethynyl-1,3-butadiene (DEBD) class is reported. The synthesis involves a one-pot, twofold Sonogashira-type, Pd⁰ -catalyzed coupling of two terminal alkynes and a carbonate derivative of a 2-butyne-1,4-diol. The synthesis is broad in scope and members of this structural family are kinetically stable enough to be handled using standard laboratory techniques at ambient temperature. They decompose primarily through heat-promoted cyclodimerizations, which are impeded by alkyl substitution and accelerated by aryl or alkenyl substitution. An iterative sequence of these unprecedented Sonogashira-type couplings generates a new type of expanded dendralene. A suitably substituted DEBD carrying two terminal alkyne groups undergoes Glaser-Eglinton cyclo-oligomerization to produce a new class of expanded radialenes, which are chiral due to restricted rotation about their 1,3-butadiene units. The structural features giving rise to atropisomerism in these compounds are distinct from those reported previously.

γ-Graphyne nanotubes as defect-free catalysts of the oxygen reduction reaction: a DFT investigation

γGyNTs as excellent metal-free ORR catalysts without any defects.

Unlocking Acyclic π-Bond Rich Structure Space with Tetraethynylethylene-Tetravinylethylene Hybrids

Literature reports describe tetraethynylethylene (TEE) as unstable but tetravinylethylene (TVE) as stable. The stabilities of these two known compounds are reinvestigated, along with those of five unprecedented TEE-TVE hybrid compounds. The five new C₁₀ hydrocarbons possess a core, tetrasubstituted C═C bond carrying all possible combinations of vinyl and ethynyl groups. A unified strategy is described for their synthesis, whereupon cross-conjugated ketones are dibromo-olefinated then cross-coupled. Due to an incorrect but nonetheless widely held belief that acyclic π-bond rich hydrocarbons are inherently unstable, a standardized set of robustness tests is introduced. Whereas only TVE survives storage in neat form, all seven hydrocarbons are remarkably robust in dilute solution, generally surviving exposure to moderate heat, light, air, and acid. The first X-ray crystal structure of TEE is reported. Subgroups of hybrids based upon conformational preferences are identified through electronic absorption spectra and associated computational studies. These new acyclic π-bond rich systems have extensive, untapped potential for the production of stable, conjugated carbon-rich materials.

Arylene Ethynylene-Functionalized Bithiazole-Based Zinc Polymers for Ultraefficient Photocatalytic Activity

Polymers 4 containing poly(arylene ethynylene) were synthesized and characterized systematically. Among them, 4c exhibited a remarkable H2 evolution rate (14.32 mmol h-1 g-1) with visible-light irradiation, lasting 72 h in different water qualities; the corresponding apparent quantum yield was 11.6% at 450 nm.

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.

Graphynes for Water Desalination and Gas Separation

Selective transport of mass through membranes, so-called separation, is fundamental to many industrial applications, e.g., water desalination and gas separation. Graphynes, graphene analogs yet containing intrinsic uniformly distributed pores, are excellent candidates for highly permeable and selective membranes owing to their extreme thinness and high porosity. Graphynes exhibit computationally determined separation performance far beyond experimentally measured values of commercial state-of-the-art polyamide membranes; they also offer advantages over other atomically thin membranes like porous graphene in terms of controllability in pore geometry. Here, recent progress in proof-of-concept computational research into various graphynes for water desalination and gas separation is discussed, and their theoretically predicted outstanding permeability and selectivity are highlighted. Challenges associated with the future development of graphyne-based membranes are further analyzed, concentrating on controlled synthesis of graphyne, maintenance of high structural stability to withstand loading pressures, as well asthe demand for accurate computational characterization of separation performance. Finally, possible directions are discussed to align future efforts in order to push graphynes and other 2D material membranes toward practical separation applications.

Graphynes: an alternative lightweight solution for shock protection

The excellent mechanical properties of graphyne (GY) have made it an appealing candidate in the field of impact protection. We assessed the deformation mechanisms of monolayer GY nanosheets of different morphologies, including α-GY, β-GY, γ-GY and 6612-GY, under supersonic-velocity impacts (from 1 to 6 km/s) based on in silico studies. Generally, cracks initiate at the geometry center and the nanosheet experiences significant out-of-plane deformation before the propagation of cracks. Tracking the atomic von Mises stress distribution, it is found that its cumulative density function has a strong correlation with the magnitude of the Young's modulus of the GYs. For nanosheets with a higher Young's modulus, it tends to transfer momentum at a faster rate. Thus, a better energy dissipation or delocalization is expected during impact. This study provides a fundamental understanding of the deformation and penetration mechanisms of monolayer GY nanosheets under impact, which is crucial in order to facilitate their emerging applications for impact protection.

Interfacial Synthesis of Conjugated Crystalline 2D Fluorescent Polymer Film Containing Aggregation-Induced Emission Unit

A fully conjugated 2D fluorescent film containing a tetraphenylethene (TPE) unit is constructed by Glaser-Hay coupling reaction on the surface of copper foil. A large-area, freestanding fluorescent films with an average thickness 4.5 nm can be obtained through the strategy of solid-liquid interfacial synthesis. The film and the pore structure are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS). High-resulution TEM and selected area electron diffraction (SAED) further confirm the dual pores structure with triangular- and hexagonal-shaped pores. The as-prepared 2D films exhibit excellent solid-state fluorescence emission arising from the confinement of TPE units.

The origin of intrinsic charge transport for Dirac carbon sheet materials: roles of acetylenic linkage and electron-phonon couplings

Within the past few years, intriguing graphene Dirac cones have attracted intense interest in novel two-dimensional (2D) Dirac materials as ultrahigh-mobility functional materials. In this work, the phonon-limited charge transport properties of α-graphyne (α-GY), α-graphdiyne (α-GDY), and β-graphyne (β-GY) were investigated using the Boltzmann transport equation within the first-principles framework while considering the electron-phonon coupling (EPC). Despite all three investigated compounds being 2D Dirac carbon materials, each demonstrated distinctly different carrier mobilities by one order of magnitude (2.2 × 104 cm2 V-1 s-1 for α-GY, 2.1 × 103 cm2 V-1 s-1 for α-GDY and 1.9 × 103 cm2 V-1 s-1 for β-GY at room-temperature and a carrier connection of n ∼ 3 × 1012 cm-2). The essential differences in the mobilities of these materials originated from the acetylenic linkage limiting the group velocity and the E2g phonon modes limiting the scattering time. For example, a few uniformly equivalent acetylenic linkages and E2g phonon modes tend to generate high mobilities. A simple mobility relationship was determined using the number of E2g photon modes, allowing for a quick estimation of the mobilities for Dirac materials. α-GY was identified as a promising alternative to graphene for next generation nanoelectronic devices.

Synthesis and Applications of Graphdiyne-Based Metal-Free Catalysts

The development of carbon materials offers the hope for obtaining inexpensive and high-performance alternatives to substitute noble-metal catalysts for their sustainable application. Graphdiyne, the rising-star carbon allotrope, is a big family with many members, and first realized the coexistence of sp- and sp² -hybridized carbon atoms in a 2D planar structure. Different from the prevailing carbon materials, its nonuniform distribution in the electronic structure and wide tunability in bandgap show many possibilities and special inspirations to construct new-concept metal-free catalysts, and provide many opportunities for achieving a catalytic activity comparable with that of noble-metal catalysts. Herein, the recent progress in synthetic methodologies, theoretical predictions, and experimental investigations of graphdiyne for metal-free catalysts is systematically summarized. Some new perspectives of the opportunities and challenges in developing high-performance graphdiyne-based metal-free catalysts are demonstrated.