Hybridized Carbon Atoms Research Articles

Probing the structure and dynamics of the heterocyclic PAH xanthene and its water complexes with infrared and microwave spectroscopy.

To assess the presence of oxygen-containing polycyclic aromatic hydrocarbons (OPAHs) in the interstellar medium and understand how water aggregates on an OPAH surface, we present a comprehensive gas-phase spectroscopy investigation of the OPAH xanthene (C13H10O) and its complexes with water using IR-UV ion dip spectroscopy and chirped-pulse Fourier transform microwave spectroscopy. The infrared spectrum of xanthene shows weak features at 3.42, 3.43, and 3.47 μm, which have been suggested to partly originate from vibrational modes of PAHs containing sp3 hybridized carbon atoms, in agreement with the molecular structure of xanthene. The high resolution of rotational spectroscopy reveals a tunneling splitting of the rotational transitions, which can be explained with an out-of-plane bending motion of the two lateral benzene rings of xanthene. The nature of the tunnelling motion is elucidated by observing a similar splitting pattern in the rotational transitions of the singly-substituted 13C isotopologues. The rotational spectroscopy investigation is extended to hydrates of xanthene with up to four water molecules. Different xanthene-water binding motifs are observed based on the degree of hydration, with O-H⋯π interactions becoming preferred over O-H⋯Oxanthene interactions as the degree of hydration increases. A structural comparison with water complexes of related molecular systems highlights the impact of the substrate's shape and chemical composition on the arrangement of the surrounding water molecules.

Melaminin Yerinde Polimerizasyonu ile Grafit Katmanlarının Genişletilmesi Üzerine Bir Çalışma

Graphene, renowned for its honeycomb lattice structure formed by densely packed sp2 hybridized carbon atoms, possesses exceptional electronic, thermal, chemical, and mechanical properties. The van der Waals-coupled graphene layers give rise to the well-known AB stacking, forming graphite. Despite the existence of several methods for graphite production, the production of graphene on a large scale remains challenging due to the lack of efficient techniques and the introduction of structural defects during the production process. Exfoliated graphite (EG), a potential solution, is typically derived from the thermal treatment of graphite intercalation compounds (GICs). Melamine, notably displaying significant expansion properties at low temperatures, has been used as an intercalation compound in limited studies. This study investigates the potential of melamine to induce the expansion of graphene layers when incorporated into graphite and subjected to thermal treatment. Raman and X-ray diffraction analyses were employed to assess structural changes.

Space-Confined Synthesis of Monolayer Graphdiyne in MXene Interlayer.

Graphdiyne (GDY) is an artificial carbon allotrope that is conceptually similar to graphene but composed of sp- and sp2 -hybridized carbon atoms. Monolayer GDY (ML-GDY) is predicted to be an ideal 2D semiconductor material with a wide range of applications. However, its synthesis has posed a significant challenge, leading to difficulties in experimentally validating theoretical properties. Here, it is reported that in situ acetylenic homocoupling of hexaethynylbenzene within the sub-nanometer interlayer space of MXene can effectively prevent out-of-plane growth or vertical stacking of the material, resulting in ML-GDY with in-plane periodicity. The subsequent exfoliation process successfully yields free-standing GDY monolayers with micrometer-scale lateral dimensions. The fabrication of field-effect transistor on free-standing ML-GDY makes the first measurement of its electronic properties possible. The measured electrical conductivity (5.1 × 103 S m-1 ) and carrier mobility (231.4 cm2 V-1 s-1 ) at room temperature are remarkably higher than those of the previously reported multilayer GDY materials. The space-confined synthesis using layered crystals as templates provides a new strategy for preparing 2D materials with precisely controlled layer numbers and long-range structural order.

Portable graphene oxide modified immunosensor for the detection of Vitamin D3

The prompt asserts that identifying low levels of vitamin D (hypovitaminosis D) in pregnant women and infants at an early stage is crucial due to the irreversible clinical consequences that can result. The measurement of 25-hydroxy Vitamin D3 levels can serve as a valuable indicator of the risk of developing Vitamin D deficiency. Graphene, a two-dimensional material composed of sp2 hybridized carbon atoms, is highly regarded due to its exceptional thermal, electronic, optical and mechanical properties, as well as its single-atom thickness and large surface area. In this investigation, graphene oxide (GO) were incorporated into paper electrodes, creating a cost-effective material that served as a matrix for developing an immunosensor. Using modified Hummer’s method, graphene oxide was synthesized and subsequently drop-cast onto the surface of a screen-printed paper electrode (SPPE), resulting in enhanced electrochemical signal. Thereafter, SPPE was modified with graphene oxide (GO) and further functionalized with 25-hydroxy Vitamin D3 monoclonal antibody using cross-linking chemistry of EDC:NHS. To characterize the synthesized GO, various analytical techniques were employed, including UV–Vis, FT-IR, Particle Size Analyser, Raman analysis, FE-SEM, TEM and XRD analyses. The stratified modification of the electrode surface was monitored through FT-IR and EIS techniques. Finally, the sensor response was measured after hybridization with different antigen concentrations by CV and DPV analyses. For electrochemical measurements, “K3[Fe (CN)6]3-/4- (5 mM in PBS buffer, pH 7.2)” was utilized as a redox indicator. The developed smart phone android based immunosensor showed a sensitivity of 2036.12µA/mm2/fg and LOD 5.96 fg/µL for electrochemical detection of vitamin D3.

Unveiling the sp2 ─sp3 C─C Polar Bond Induced Electromagnetic Responding Behaviors by a 2D N-doped Carbon Nanosheet Absorber.

The infertile electromagnetic (EM) attenuating behavior of carbon material makes the improvement of its performance remain a significant challenge. Herein, a facile and low-cost strategy radically distinct from the prevalent approaches by constructing polar covalent bonds between sp2 -hybridized and sp3 -hybridized carbon atoms to introduce strong dipolar polarization is proposed. Through customizing and selectively engineering the N moieties conjugated with carbon rings, the microstructure of the as-synthesized 2D nanosheet is gradually converted with the partial transition from sp3 carbons to sp2 carbons, where the electric dipoles between them are also tuned. Supported by the DFT calculations, a progressively enhanced sp2 ─sp3 C─C dipolar polarization is caused by this controllable structure evolution, which is demonstrated to contribute dominantly to the total dielectric loss. By virtue of this unduplicated loss behavior, a remarkable effective absorption bandwidth (EAB) beyond -10dB of 8.28GHz (2.33mm) and an ultrawide EAB beyond -5dB of 13.72GHz (4.93mm) are delivered, which upgrade the EM performance of carbon material to a higher level. This study not only demonstrates the huge perspective of sp2 ─sp3 -hybridized carbon in EM elimination but also gives pioneering insights into the carbon-carbon polarization mechanism for guiding the development of advanced EM absorption materials.

Controlling adhesion and thermal stability of tetrahedral amorphous carbon coatings with intermediate sp3C fraction

Tetrahedral amorphous carbon (ta-C) coatings with an intermediate sp3C fraction were deposited on single-crystal silicon wafer substrates via intermittent filtered cathode vacuum arc (FCVA) deposition. The ta-C layer thickness and sp3C fraction in the coatings were adjusted using the deposition duration and bias voltage applied to the substrate, respectively. Some of the coated specimens were annealed at 300 and 600 °C for 4 h in a 5-Pa vacuum. The morphologies and microstructures of the specimens were characterized using scanning electron microscopy and transmission electron microscopy. The hybridization of carbon atoms was analyzed using X-ray photoelectron spectroscopy and micro-Raman spectroscopy. The mechanical characteristics of the coatings, including the critical adhesion load between the coatings and substrates, residual stress in the coatings, and hardness, were characterized. For the specimens deposited by the same bias voltage, even their top ta-C layer thickness ranged from approximately 500 nm to 1500 nm, their residual compressive stress in the coatings was maintained at a low value by the intermittent deposition of FCVA, which varied slightly with the coating thickness. The adhesion strength was improved by increasing the thickness of the as-deposited coating from approximately 12 to 40 N. The residual compressive stress of the post-annealing specimens with sp3C fraction of 45–53.8 % exhibited monotonously increasing or V-shaped variation with increasing annealing temperature. Herein, the underlying mechanisms are discussed in detail.

A review on synthesis of graphene oxide and its functionalization through ion irradiation methods

Graphene is a monoatomic layer of sp2 hybridized carbon atoms, which is two-dimensional and has unique electrical, magnetic and mechanical properties. Pristine graphene is inert in nature and limited in its applications. Doping can enhance the properties of graphene. Several efforts have been done recently to tune its properties through doping, which will provide precise control over its structure and properties. In this review, different methods of doping graphene especially chemical versus irradiation methods and their effects are summarized. Moreover, the advantages of ion irradiation techniques in doping are also discussed based on the available experimental results.

Theoretical characterization of tolanene: A new 2D sp-sp2 hybridized carbon allotrope

The search for new carbon allotrope forms has been the focus of much experimental and theoretical research. Some nonbenzenoid sp2-hybridized carbon allotropes have been proposed and synthesized, revealing properties unlike those observed for graphene. In the present work, first-principles calculations were performed to investigate a new two-dimensional (2D) carbon sheet — named tolanene — which may hypothetically be obtained from diphenylacetylene molecules as building blocks. The nonbenzenoid tolanene sheet has a periodic arrangement of four-, six-, eight-, and twelve-membered rings of sp and sp2 hybridized carbon atoms. Our calculations reveal that tolanene is mechanically and dynamically stable, and can potentially withstand a temperature as high as 1500 K quite easily. The structure presents a strong anisotropy in its mechanical properties, in a similar fashion to biphenylene. Additionally, we verify that the structure presents a metallic behavior, and its low-energy electronic structure is fully determined by pz orbitals, as in most carbon-based 2D materials. The application of tolanene as a potential anode material in Li-ion batteries is also explored. We find that it offers a competitive Li storage capacity and fast Li mobility along with other interesting electronic properties.

Elucidating the Excited State Behavior of Pyridyl Pyridinium Systems via Computational and Transient Absorption Studies of Tetrahedral Multichromophoric Arrays and their Model Compounds.

The tetrahedral shape-persistent molecule 14+ , containing four identical pyridyl pyridinium units connected via a sp3 hybridized carbon atom, has been investigated in detail by means of steady-state and time resolved spectroscopy. Remarkable photophysical properties are observed, particularly in comparison with protonated and methylated analogues (1H4 8+ , 1Me4 8+ ), which exhibit substantially shorter excited state lifetimes and lower emission quantum yields. Theoretical studies have rationalized the behavior of the tetrameric molecules relative to the monomers, with DFT and TD-DFT calculations corroborating steady-state (absorption and emission) and transient absorption spectra. The behavior of the monomeric compounds (each consisting in one of the four identical subunits of the tetramers, i. e., 2+ , 2H2+ and 2Me2+ ) considerably differs from that of the tetramers, indicating a strong electronic interaction between the subunits in the tetrameric species, likely promoted by the homoconjugation through the connecting sp3 C atom. 2+ is characterized by a peculiar S1 -S2 excited state inversion, whereas the short-lived emitting S1 state of 2H2+ and 2Me2+ exhibits a partial charge-transfer character, as substantiated by spectro-electrochemical studies. Among the six investigated systems, only 14+ is a sizeable luminophore (Φem =0.15), which is related to the peculiar features of its singlet state.

The synthesis of MNC5 active site for electrochemical catalysis

Metal-nitrogen-carbon (M-N-C) catalysts with M-Nx (x = 2 or 4) sites on graphene substrate are researched intensively nowadays. However, the simple and repetitive hexatomic ring structure of graphene limits the exploration of novel efficient active sites for catalysis. Herein, a new carbon material, hydrogen-substituted graphdiyne (HsGDY), is designed as the substrate to develop new active sites. Benefiting from the unique sp and sp2 hybridized carbon atoms of HsGDY, aromatic rings in HsGDY can fix Fe single atoms, creating novel FeC6 and FeNC5 active sites. The as-synthesized Fe-N-HsGDY catalyst displays much higher activity than commercial Pt/C and is found to be one of the highest activities among the reported non-noble metal catalysts for oxygen reduction reaction (ORR). FeNC5 site with graphitic-N has been verified experimentally and theoretically as an efficient active site for ORR. Those results indicate that the rational choice of specific substrate materials with novel structures will broaden the path of creating new active sites with efficient activity.

Rational Fabrication of Fe3O4/Co3O4/Graphdiyne Tandem Heterojunction toward Optimized Photocatalytic Hydrogen Evolution

Graphdiyne (GDY) is a novel two‐dimensional material composed of sp and sp2 hybridized carbon atoms. Herein, GDY nanosheets are prepared from tribromobenzene by a simple ball‐milling‐assisted reduction–elimination method and is introduced into Fe3O4 colloidal spheres and Co3O4 cubes by low‐temperature mixing to efficiently synthesize Fe3O4/Co3O4/GDY tandem heterojunction photocatalysts. The hydrogen evolution activity of the optimized catalyst is 4.02 mmol g−1 h−1 under visible light (λ ≥ 420 nm), which is 100.05, 10.05, and 3.65 times higher than that of Fe3O4 (0.04 mmol g−1 h−1), Co3O4 (0.40 mmol g−1 h−1), and GDY (1.10 mmol g−1 h−1), respectively. In addition, the Prussian blue analog (PBA)‐derived Co3O4 improves the light‐harvesting efficiency and reaction kinetics. More importantly, the establishment of tandem heterojunctions prompts energy‐level alignment and optimizes charge multichannel transfer, which is the dominant factor for enhanced photocatalytic activity. Combined with time‐resolved photoluminescence spectra, valence band X‐Ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and density functional theory calculations, the possible mechanism of Fe3O4/Co3O4/GDY series heterojunction is proposed and elucidated. This work provides a new idea for the construction of tandem heterojunctions based on graphdiyne and PBA derivatives.

Deposition of nanometer-thick amorphous carbon films by filtered cathodic vacuum arc under oblique ion incidence conditions

Filtered cathodic vacuum arc (FCVA) is a promising technique for synthesizing extremely thin carbon films exhibiting highly tetrahedral (sp3) carbon atom hybridization. However, most FCVA studies are for incident ions impinging perpendicular to the substrate surface. In this study, the effects of the ion incidence angle on the thickness, structure, and surface roughness of amorphous carbon (a-C) films deposited under different substrate bias voltages were examined in the light of computational and experimental results. Dynamic simulations and film thickness measurements showed a decrease in film thickness with increasing ion incidence angle, attributed to the decrease in carbon ion fluence on the film surface. Carbon atom hybridization analysis revealed a critical ion incidence angle for a given substrate bias voltage. Simulation and experimental results demonstrated that the enhancement of sp3 hybridization resulted from carbon-carbon collision cascades on the growing film surface and densification induced by direct and recoil implantation processes controlled by the ion incidence angle and substrate bias voltage. The strong dependence of a-C film growth on the carbon ion incidence angle exemplified by the results of this study has direct implications in the oblique deposition of ultrathin a-C films with predominant tetrahedral carbon atom hybridization. The present study provides a framework for optimizing the ion incidence angle to achieve the deposition of a-C ultrathin films with high sp3 contents.

Microfluidic-Assisted Alignment of Graphene Nanosheets for Microfiber Formation

Recently, our lab developed graphene oxide microfibers for ultrasensitive neurochemical detection with fast-scan cyclic voltammetry (FSCV). Graphene-fiber microelectrodes provide a significant advance over traditional carbon-fiber microelectrodes due to their resistance to detrimental fouling, fast electron transfer kinetics, and frequency independent behavior. Despite our recent advancement, there still exists a gap in our understanding of how specific changes in the carbon chemical structure influences adsorption and interaction of various neurochemicals at the surface. Understanding the extent to which the carbon chemical structure influences electrochemical detection is critical for designing tailor-made electrodes for ultrasensitive analyte detection. From a molecular level point-of-view, the graphene sheet consists of two regions with different structure: i) the basal plane, consisting of conjugated sp2 hybridized carbon atoms, and characterized by an atomic flatness and low defect density; and ii) the edge plane, that forms sp3 sites with a high level of defects and a variety of functional groups and dangling bonds. It is generally believed that the electrochemical properties of the basal and edge plane are significantly different, however, there has been debate concerning the electrochemical activity at the basal and edge plane. The conventional consensus is that electron transfer kinetics is faster on the edge plane in comparison with the basal plane sites, while the opposite barrier of this debate provides evidence for fast electron transfer at pristine basal plane. Moreover, how these factors influence neurochemical detection, particularly at rapid scan rates, is still lacking due to the necessity of using microelectrodes with FSCV. To date, most studies analyzing the influence of basal vs. edge plane surfaces on electrochemical detection have used macroelectrodes like highly ordered pyrolytic graphite (HOPG) which are not amenable to FSCV detection due to the large capacitive currents obtained at macroelectrodes at scan rates consisting of hundreds of volts per second. Therefore, to address this existing knowledge gap in understanding how edge vs. basal planes influence subsecond neurochemical detection, the ability to develop microelectrodes with controlled surfaces is crucial. Here, I will discuss our labs latest effort in developing graphene oxide microfibers with controllable nanosheet alignment to study the influence of basal vs. edge plane availability on neurochemical detection at rapid scan rates. To assist in nanosheet alignment, we use microfluidic channels to assist in fluid-driven control of nanosheet orientation. Using microfluidics to help develop highly controllable electrode materials provides a critical advance in our ability to develop novel carbon surfaces for detection.

Graphdiyne and its Composites for Lithium-Ion and Hydrogen Storage.

Graphynes (GYs) are a novel type of carbon allotrope composed of sp and sp2 hybridized carbon atoms, boasting both a planar conjugated structure akin to graphene and a pore-like configuration in three-dimensional space. Graphdiyne (GDY), the first successfully synthesized member of GYs family, has gained much interest due to its fascinating electrochemical properties including a greater theoretical capacity, high charge mobility and advanced electronic transport properties, making it a promising material for energy storage applications for lithium-ion and hydrogen storage. Various methods, including heteroatom substitution, embedding, strain, and nanomorphology control, have been employed to further enhance the energy storage performance of GDY. Despite the potential of GDY in energy storage applications, there are still challenges to overcome in scaling up mass production. This review summarizes recent progress in the synthesis and application of GDY in lithium-ion and hydrogen storage, highlighting the obstacles faced in large-scale commercial application of GDY-based energy storage devices. Suggestions on possible solutions to overcome these hurdles have also been provided. Overall, the unique properties of GDY make it a promising material for energy storage applications in lithium-ion and hydrogen storage devices. The findings presented here will inspire further development of energy storage devices utilizing GDY.

High pressure and high temperature phase transformations of covalent triazine-based frameworks

A monolithic two-dimensional (2D) biphenyl-linked triazine-based framework (CTF-2) showing merely slight crystallinity was prepared by Lewis acid-promoted polymerisation of 4,4′-biphenyldicarbonitrile in liquid TiCl4 at moderate temperature to avoid unwanted carbonization. The transformations of CTF-2 induced by high pressure (up to 60 GPa) and temperature (up to 2400 K) were studied by IR and in situ Raman spectroscopy as well as TEM microscopy. In contrast to graphitic C3N4 materials, CTF-2 exhibits high optical density and reduced fluorescence at high pressure, allowing laser-induced sample heating. Spectral data show the formation of sp3 hybridised carbon atoms and triazine ring distortion in CTF-2 material at pressures above 17 GPa. According to the pressure Raman effect, the bulk modulus of the high-pressure phase of CTF-2 (high-pressure phase CTF-2) was found to be 570 ± 10 GPa, which is a typical value for superhard carbon materials. Structural studies revealed nitrogen preservation in the specimen after high-pressure treatment and stability of the disordered sp3 states of the high-pressure phase CTF-2 in the quenched specimen. This behaviour is quite different from that of the quenched disordered sp3 states of high pressure pure carbon phases, which convert to the sp2 state at pressures below 3–7 GPa.

Efficient C(sp3)-H Carbonylation of Light and Heavy Hydrocarbons with Carbon Monoxide via Hydrogen Atom Transfer Photocatalysis in Flow.

Despite their abundance in organic molecules, considerable limitations still exist in synthetic methods that target the direct C-H functionalization at sp3-hybridized carbon atoms. This is even more the case for light alkanes, which bear some of the strongest C-H bonds known in Nature, requiring extreme activation conditions that are not tolerant to most organic molecules. To bypass these issues, synthetic chemists rely on prefunctionalized alkyl halides or organometallic coupling partners. However, new synthetic methods that target regioselectively C-H bonds in a variety of different organic scaffolds would be of great added value, not only for the late-stage functionalization of biologically active molecules but also for the catalytic upgrading of cheap and abundant hydrocarbon feedstocks. Here, we describe a general, mild and scalable protocol which enables the direct C(sp3)-H carbonylation of saturated hydrocarbons, including natural products and light alkanes, using photocatalytic hydrogen atom transfer (HAT) and gaseous carbon monoxide (CO). Flow technology was deemed crucial to enable high gas-liquid mass transfer rates and fast reaction kinetics, needed to outpace deleterious reaction pathways, but also to leverage a scalable and safe process.

Regulating Efficient and Selective Single-atom Catalysts for Electrocatalytic CO2 Reduction.

Anchoring transition metal (TM) atoms on suitable substrates to form single-atom catalysts (SACs) is a novel approach to constructing electrocatalysts. Graphdiyne with sp-sp2 hybridized carbon atoms and uniformly distributed pores have been considered as a potential carbon material for supporting metal atoms in a variety of catalytic processes. Herein, density functional theory (DFT) calculations were performed to study the single TM atom anchoring on graphdiyne (TM1 -GDY, TM=Sc, Ti, V, Cr, Mn, Co and Cu) as the catalysts for CO2 reduction. After anchoring metal atoms on GDY, the catalytic activity of TM1 -GDY (TM=Mn, Co and Cu) for CO2 reduction reaction (CO2 RR) are significantly improved comparing with the pristine GDY. Among the studied TM1 -GDY, Cu1 -GDY shows excellent electrocatalytic activity for CO2 reduction for which the product is HCOOH and the limiting potential (UL ) is -0.16 V. Mn1 -GDY and Co1 -GDY exhibit superior catalytic selectivity for CO2 reduction to CH4 with UL of -0.62 and -0.34 V, respectively. The hydrogen evolution reaction (HER) by TM1 -GDY (TM=Mn, Co and Cu) occurs on carbon atoms, while the active sites of CO2 RR are the transition metal atoms . The present work is expected to provide a solid theoretical basis for CO2 conversion into valuable hydrocarbons.

Activation behavior of Cu0/FeS/N-graphene derived from waste soybean residue for peroxymonosulfate: Performance and mechanism

Nitrogen-enriched graphene grown on zero valent copper (Cu0) and loaded with iron sulfide (FeS) was prepared through a pyrolysis-liquid phase exfoliation process using waste soybean residue as the precursor biomass. Graphene-based catalyst (GBC) exhibits exceptional proficiency as a peroxymonosulfate activator, displaying a remarkable removal surpassing 90% of total petroleum hydrocarbons (TPHs) in 180 min. Reactive oxygen species were identified through masking experiments and electron paramagnetic resonance analysis in the Cu0/FeS/BC-900/PMS system. S(II) was the source of power for the conversion of Fe(III) to Fe(II), and it was also the reason for the continuous generation of SO4•− in the system. Density functional theory calculations revealed the active sites for adsorption and reaction. The presence of SO4•−, O2•−, and 1O2 species was attributed to the elongation of S–O and O–O bonds, as well as enhancement of electrons in sulfur and sp2 hybrid carbon atoms, respectively. The degradation of TPHs was ascribed to various radical and non-radical pathways of ROSs, with SO4•− serving as the primary oxidizing species. It was fascinating that the Cu0/FeS/BC-900/PMS system exhibited good resistance to inorganic anions and surfactants, and the treatment effect on real oilfield produced wastewater was satisfactory.

Accessing three-dimensional molecular diversity through benzylic C-H cross-coupling.

Pharmaceutical and agrochemical discovery efforts rely on robust methods for chemical synthesis that rapidly access diverse molecules1,2. Cross-coupling reactions are the most widely used synthetic methods3, but these methods typically form bonds to C(sp2)-hybridized carbon atoms (e.g., amide coupling, biaryl coupling) and lead to a prevalence of "flat" molecular structures with suboptimal physicochemical and topological properties4. Benzylic C(sp3)-H cross-coupling methods offer an appealing strategy to address this limitation by directly forming bonds to C(sp3)-hybridized carbon atoms, and emerging methods exhibit synthetic versatility that rivals conventional cross-coupling methods to access products with drug-like properties. Here, we use a virtual library of >350,000 benzylic ethers and ureas derived from benzylic C-H cross-coupling to test the widely held view that coupling at C(sp3)-hybridized carbon atoms affords products with improved three-dimensionality. The results show that the conformational rigidity of the benzylic scaffold strongly influences the product dimensionality. Products derived from flexible scaffolds often exhibit little or no improvement in three-dimensionality, unless they adopt higher energy conformations. This outcome introduces an important consideration when designing routes to topologically diverse molecular libraries. The concepts elaborated herein are validated experimentally through an informatics-guided synthesis of selected targets and the use of high-throughput experimentation to prepare a library of three-dimensional products that are broadly distributed across drug-like chemical space.

Synthesis and Self-Assembly of Ultrathin Holey Graphdiyne Nanosheets for Oxygen Reduction Reaction.

Graphdiyne (GDY) is a fascinating graphene-like 2D carbon allotrope comprising sp and sp2 hybridized carbon atoms. However, GDY materials synthesized by solution-phase methods normally come as thick and porous films or amorphous powders with severely disordered stacking modes that obstruct macroscopic applications. Here, a facile and scalable synthesis of ultrathin holey graphdiyne (HGDY) nanosheets is reported via palladium/copper co-catalyzed homocoupling of 1,3,5-triethynylbenzene. The resulting freestanding 2D HGDY self-assembles into 3D foam-like networks which can in situ anchor clusters of palladium atoms on their surfaces. The Pd/HGDY hybrids exhibit high electrocatalytic activity and stability for the oxygen reduction reaction which outperforms that of Pt/C benchmark. Based on the ultrathin graphene-like sheets and their unique 3D interconnected macrostructures, Pd/HGDY holds great promise for practical electrochemical catalysis and energy-related applications.