Defect‐Rich Graphene Nanomesh Produced by Thermal Exfoliation of Metal–Organic Frameworks for the Oxygen Reduction Reaction

Although graphene nanomesh is an attractive 2D carbon material, general synthetic routes to produce functional graphene nanomesh in large‐scale are complex and tedious. Herein, we elaborately design a simple two‐step dimensional reduction strategy for exploring nitrogen‐doped graphene nanomesh by thermal exfoliation of crystal‐ and shape‐modified metal‐organic frameworks (MOFs). MOF nanoleaves with 2D rather than 3D crystal structure are used as the precursor, which are further thermally unraveled into nitrogen‐doped graphene nanomesh by using metal chlorides as the exfoliators and etching agent. The nitrogen‐doped graphene nanomesh has a unique ultrathin two‐dimensional morphology, high porosity, rich and accessible nitrogen‐doped active sites, and defective graphene edges, contributing to an unprecedented catalytic activity for the oxygen reduction reaction (ORR) in acid electrolytes. This approach is suitable for scalable production.     

Facile synthesis of magnetic zinc metal‐organic framework for extraction of nitrogen‐containing heterocyclic fungicides from lettuce vegetable samples

We present a simple method for the fabrication of a magnetic amino‐functionalized zinc metal‐organic framework based on a magnetic graphene oxide composite. The resultant framework exhibited a porous 3D structure, high surface area and good adsorption properties for nitrogen‐containing heterocyclic fungicides. The adsorption process and capacity indicated that the primary adsorption mechanism might be hydrogen bonding and π‐π conjugation. In addition, an optimized protocol for magnetic solid phase extraction was developed (such as adsorbent content, pH, and desorption solvent), and utilized for the extraction of nitrogen‐containing heterocyclic fungicides from vegetable samples. Quantitation by high performance liquid chromatography coupled with tandem mass spectrometry offered a detection limit of 0.21–1.0 μg/L (S/N = 3) with correlation coefficients larger than 0.9975. These results demonstrate that magnetic amino‐functionalized zinc metal‐organic framewor is a promising adsorbent for the extraction and quantitation of nitrogen‐containing heterocyclic fungicides.     

N2: a potential pitfall for bulk 2H isotope analysis of explosives and other nitrogen‐rich compounds by continuous‐flow isotope‐ratio mass spectrometry

Observations made during the ¹³C isotope analysis of gaseous CO₂ in the simultaneous presence of argon in the ion source of the isotope ratio mass spectrometer prompted us to investigate what influence the simultaneous presence of nitrogen would have on both accuracy and precision of bulk ²H isotope analysis of nitrogen‐rich organic compounds. Initially an international reference material, IAEA‐CH7, was mixed with silver nitrate in various ratios to assess the impact that N₂ evolved from the pyrolysis of nitrogen‐rich organic compounds would have on measured δ²H‐values of IAEA‐CH7. In a subsequent experiment, benzoic acid was mixed with silver nitrate to mimic the N:H ratio of organic‐rich nitrogen compounds such as cellulose nitrate and RDX. The results of both experiments showed a significant deterioration of both accuracy and precision for the expected δ²H values for IAEA‐CH7 and benzoic acid when model mixtures were converted into hydrogen and nitrogen, and subsequently separated by gas chromatography using standard experimental conditions, namely a 60 cm packed column with molecular sieve 5 Å as stationary phase held at a temperature of 85°C. It was found that bulk ²H stable isotope analysis of nitrogen‐rich organic compounds employing published standard conditions can result in a loss of accuracy and precision yielding δ²H values that are 5 to 25‰ too negative, thus suggesting, for example, that tree‐ring ²H isotope data based on cellulose nitrate may have to be revised. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and Exploration of Ladder‐Structured Large Aromatic Dianhydrides as Organic Cathodes for Rechargeable Lithium‐Ion Batteries

Compared to anode materials in Li‐ion batteries, the research on cathode materials is far behind, and their capacities are much smaller. Thus, in order to address these issues, we believe that organic conjugated materials could be a solution. In this study, we synthesized two non‐polymeric dianhydrides with large aromatic structures: NDA‐4N (naphthalenetetracarboxylic dianhydride with four nitrogen atoms) and PDA‐4N (perylenetetracarboxylic dianhydride with four nitrogen atoms). Their electrochemical properties have been investigated between 2.0 and 3.9 V (vs. Li⁺/Li). Benefiting from multi‐electron reactions, NDA‐4N and PDA‐4N could reversibly achieve 79.7 % and 92.3 %, respectively, of their theoretical capacity. Further cycling reveals that the organic compound with a relatively larger aromatic building block could achieve a better stability, as an obvious 36.5 % improvement of the capacity retention was obtained when the backbone was switched from naphthalene to perylene. This study proposes an opportunity to attain promising small‐molecule‐based cathode materials through tailoring organic structures.     

Visible‐light‐driven self‐cleaning SERS substrate of silver nanoparticles and graphene oxide decorated nitrogen‐doped titania nanotube array

Graphene oxide (GO) and silver nanoparticles (Ag NPs) sequentially decorated nitrogen‐doped titania nanotube array (N‐TiO₂ NTA) had been designed as visible‐light‐driven self‐cleaning surface‐enhanced Raman scattering (SERS) substrate for a recyclable SERS detection application. N‐TiO₂ NTA was fabricated by anodic oxidation and then doping nitrogen treatment in ammonia atmosphere, acting as a visible‐light‐driven photocatalyst and supporting substrate. Ag/GO/N‐TiO₂ NTA was prepared by decorating GO monolayer through an impregnation process and then depositing Ag NPs through a polyol process on the surface of N‐TiO₂ NTA, acting as the collection of organic molecule and Raman enhancement. The SERS activity of Ag/GO/N‐TiO₂ NTA was evaluated using methyl blue as an organic probe molecule, revealing the analytical enhancement factor of 4.54 × 10⁴. Ag/GO/N‐TiO₂ NTA was applied as active SERS substrate to determine a low‐affinity organic pollutant of bisphenol A, revealing the detection limit of as low as 5 × 10^?7 m . Ag/GO/N‐TiO₂ NTA could also achieve self‐cleaning function for a recycling utilization through visible‐light‐driven photocatalytic degradation of the adsorbed organic molecules. Ag/GO/N‐TiO₂ NTA has been successfully reused for five times without an obvious decay in accuracy and sensitivity for organic molecule detection. The unique properties of this SERS substrate enable it to have a promising application for the sensitive and recyclable SERS detection of low‐affinity organic molecules. Copyright © 2016 John Wiley & Sons, Ltd.     

Metal‐Nitrogen‐doped Porous Carbons Derived from Metal‐Containing Ionic Liquids for Oxygen Reduction Reaction

This study describes a self‐doping and additive‐free strategy for the synthesis of metal‐nitrogen‐doped porous carbon materials (CMs) via carbonizing well‐tailored precursors, metal‐containing ionic liquids (M‐ILs). The organic skeleton in M‐ILs serves as both carbon and nitrogen sources, while metal ions acts as porogen and metallic dopants. A high nitrogen content, appropriate content of metallic species and hierarchical porosity synergistically endow the resultant CMs (MIBA‐M‐T) as effective electrocatalysts for the oxygen reduction reaction (ORR). MIBA‐Fe‐900 with a high specific surface area of 1567 m² g^?1 exhibits an activity similar to that of Pt/C catalyst, a higher tolerance to methanol than Pt/C, and long‐term durability. This work supplies a simple and convenient route for the preparation of metal‐containing carbon electrocatalysts.     

The Assembly of Supramolecular Boxes and Coordination Polymers Based on Bis‐Zinc‐Salphen Building Blocks

We report the assembly of supramolecular boxes and coordination polymers based on a rigid bis‐zinc(II)‐salphen complex and various ditopic nitrogen ligands. The use of the bis‐zinc(II)‐salphen building block in combination with small ditopic nitrogen ligands gave organic coordination polymers both in solution as well as in the solid state. Molecular modeling shows that supramolecular boxes with small internal cavities can be formed. However, the inability to accommodate solvent molecules (such as toluene) in these cavities explains why coordination polymers are prevailing over well‐defined boxes, as it would lead to an energetically unfavorable vacuum. In contrast, for relatively longer ditopic nitrogen ligands, we observed the selective formation of supramolecular box assemblies in all cases studied. The approach can be easily extended to chiral analogues by using chiral ditopic nitrogen ligands.     

Nitrenium Salts in Lewis Acid Catalysis

Molecular compounds featuring nitrogen atoms are typically regarded as Lewis bases and are extensively employed as donor ligands in coordination chemistry or as nucleophiles in organic chemistry. By contrast, electrophilic nitrogen‐containing compounds are much rarer. Nitrenium cations are a new family of nitrogen‐based Lewis acids, the reactivity of which remains largely unexplored. In this work, nitrenium ions are explored as catalysts in five organic transformations. These reactions are the first examples of Lewis acid catalysis employing nitrogen as the site of substrate activation. Moreover, these compounds are readily accessed from commercially available reagents and exhibit remarkable stability toward moisture, allowing for benchtop transformations without the need to pretreat solvents.     

On‐Surface Bottom‐Up Synthesis of Azine Derivatives Displaying Strong Acceptor Behavior

On‐surface synthesis is an emerging approach to obtain, in a single step, precisely defined chemical species that cannot be obtained by other synthetic routes. The control of the electronic structure of organic/metal interfaces is crucial for defining the performance of many optoelectronic devices. A facile on‐surface chemistry route has now been used to synthesize the strong electron‐acceptor organic molecule quinoneazine directly on a Cu(110) surface, via thermally activated covalent coupling of para‐aminophenol precursors. The mechanism is described using a combination of in situ surface characterization techniques and theoretical methods. Owing to a strong surface‐molecule interaction, the quinoneazine molecule accommodates 1.2 electrons at its carbonyl ends, inducing an intramolecular charge redistribution and leading to partial conjugation of the rings, conferring azo‐character at the nitrogen sites.     

Templated Synthesis of Nitrogen‐Enriched Nanoporous Carbon Materials from Porogenic Organic Precursors Prepared by ATRP

A facile templated synthesis of functional nanocarbon materials with well‐defined spherical mesopores is developed using all‐organic porogenic precursors comprised of hairy nanoparticles with nitrogen‐rich polyacrylonitrile shells grafted from sacrificial cross‐linked poly(methyl methacrylate) cores (xPMMA‐g‐PAN). Such shape‐persistent all‐organic nanostructured precursors, prepared using atom transfer radical polymerization (ATRP), assure robust formation of template nanostructures with continuous PAN precursor matrix over wide range of compositions, and allow for removal of the sacrificial template through simple thermal decomposition. Carbon materials prepared using this method combine nitrogen enrichment with hierarchical nanostructure comprised of microporous carbon matrix interspersed with mesopores originating from sacrificial xPMMA cores, and thus perform well as CO₂ adsorbents and as supercapacitor electrodes.     

Preparation of Heteroaromatic (Aryl)iodonium Imides as I−N Bond‐Containing Hypervalent Iodine

Hypervalent iodine(III) compounds containing iodine–nitrogen bonds are very attractive amination reagents in organic synthesis. Heteroaromatic (aryl)iodonium imides containing a iodine–nitrogen bond and a hypervalent iodine(III) atom were prepared from heteroarenes, bis(sulfon)imides and (diacetoxyiodo)arenes under mild conditions. These compounds were stable under air and in organic solvents, and could be easily purified by precipitation. X‐ray crystal structure analysis indicated that the structure of N‐pivaloyl indolyl(phenyl)iodonium bis(tosyl)imides and N‐pivaloyl indolyl(2‐butoxyphenyl)iodonium bis(tosyl)imides was a dimer with a T‐shaped geometry at the iodine atom linked to an indole group and a bis(tosyl)imide by a monomer unit. Moreover, the use of substituted iodoarenes facilitated the purification of some of the heteroaromatic (aryl)iodonium imides.     

Synthesis and characterization of a bis‐(4‐trifluoromethanesulfonyloxyphenyl)phenylamine monomer and its polymer for light‐emitting applications

This study focuses on the preparation, polymerization, characterization, and optical properties of a new bis‐(4‐trifluoromethanesulfonyloxyphenyl)phenylamine monomer. This is the first nitrogen‐containing monomer having nitrogen atoms as bridges between phenyl rings, and it was synthesized in three steps. The polymerization was carried out through the Ni(0)‐catalyzed homocoupling reaction of the bis‐(4‐trifluoromethanesulfonyloxyphenyl)phenylamine compound. The resulting polymer, polybis(paraphenyl)phenylamine, emitted an intense blue color (where λ = 415 nm) upon irradiation by ultraviolet light. The photoluminescence quantum yield was found to be 36% with a long excited‐state lifetime of 3.3 ns. Electrical conductivity data for an HCl‐doped film of the polymer were also examined. This novel polymer is of interest as an organic emitting material for electroluminescent devices. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1860–1867, 2007     

New Core-Shell Type Polymeric Supports Based on the Amberlite XAD-4 Adsorbent: A Novel Synthesis Procedure

The chloromethyl groups have been introduced into commercial S/DVB copolymer matrixes via interpenetrating polymer networks (IPN) synthesis. The procedure involves impregnation of the Amberlite XAD‐4 adsorbent, with use of the vinylbenzyl chloride (VBC) and divinylbenzene (DVB) monomers mixture, and suspension polymerization process. The syntheses were evaluated by FT‐IR spectra and SEM analyses and furthermore by chlorine content determination as well as characterization of porous structure by nitrogen adsorption at liquid nitrogen temperature. Designed synthesis approach allowed determining organic and water phases composition. Furthermore, impact of an excess of the organic phase removal method has been investigated. Basing on the obtained results it could be stated that the chloromethyl groups, derived from VBC monomer, were successfully introduced into the XAD‐4 structure. Captured SEM images revealed significant changes in the beads' surface morphology after polymerization processes. The presented studies reveal designed and executed synthesis processes, which involve the use of a proper water phase and excess of organic phase removal. Observed changes in the beads' morphology suggest that introduced functionalities are concentrated on the porous surface of the XAD‐4 adsorbent.     

Highly Efficient Electrocatalysts for Oxygen Reduction Based on 2D Covalent Organic Polymers Complexed with Non‐precious Metals

A class of 2D covalent organic polymers (COPs) incorporating a metal (such as Fe, Co, Mn) with precisely controlled locations of nitrogen heteroatoms and holes were synthesized from various N‐containing metal–organic complexes (for example, metal–porphyrin complexes) by a nickel‐catalyzed Yamamoto reaction. Subsequent carbonization of the metal‐incorporated COPs led to the formation of COP‐derived graphene analogues, which acted as efficient electrocatalysts for oxygen reduction in both alkaline and acid media with a good stability and free from any methanol‐crossover/CO‐poisoning effects.     

Constant Current Chronopotentiometric Stripping Analysis of ‘N‐Catalyst’ in Sodium Chloride Solution and Seawater

Catalytic properties and surface activity of nitrogen containing polymeric organic material (N‐POM) were analyzed by constant current chronopotentiometric stripping analysis (CPSA) and alternating current (AC) voltammetry in sodium chloride solution (pH 8) and seawater. CPSA proved to be a suitable method for determination of low concentrations of N‐POM in seawater by measuring its ‘presodium’ catalytic peak H. A protein human serum albumin (HSA) (15% of N) was used as a model compound and the concentration of N‐POM from natural seawater samples was expressed in HSA concentration equivalents. Peak H represents an additional parameter for characterization of natural organic matter.     

Designed Precursor for the Controlled Synthesis of Highly Active Atomic and Sub‐nanometric Platinum Catalysts on Mesoporous Silica

The development of new methods to synthesize nanometric metal catalysts has always been an important and prerequisite step in advanced catalysis. Herein, we design a stable nitrogen ligated Pt complex for the straightforward synthesis by carbonization of uniformly sized atomic and sub‐nanometric Pt catalysts supported on mesoporous silica. During the carbonization of the Pt precursor into active Pt species, the nitrogen‐containing ligand directed the decomposition in a controlled fashion to maintain uniform sizes of the Pt species. The nitrogen ligand had a key role to stabilize the single Pt atoms on a weak anchoring support like silica. The Pt catalysts exhibited remarkable activities in the hydrogenation of common organic functional groups with turnover frequencies higher than in previous studies. By a simple post‐synthetic treatment, we could selectively remove the Pt nanoparticles to obtain a mixture of single atoms and nanoclusters, extending the applicability of the present method.     

Theoretically Rational Designs of Transport Organic Semiconductors Based on Heteroacenes

A Marcus electron transfer theory coupled with an incoherent polaron hopping and charge diffusion model in combining with first‐principle quantum chemistry calculation was applied to investigating the effects of heteroatom on the intermolecular charge transfer rate for a series of heteroacene molecules. The influences of intermolecular packing and charge reorganization energy were discussed. It was found that the sulphur and nitrogen substituted heteroacenes were intrinsically hole‐transporting materials due to the reduced hole reorganization energy and the enhanced overlap between HOMOs. For the oxygen‐substituted heteroacene, it was found that both the electronic couplings and the reorganization energies for holes and electrons were comparative, indicating the application potential of ambipolar devices. Most interestingly, for the boron‐substituted heteroacenes, theoretical calculations predicted a promising electron‐transport material, which is rare for organic materials. These findings provide insights into rationally designing organic semiconductors with specific properties.     

Organic ligand-free alkylation of amines, carboxamides, sulfonamides, and ketones by using alcohols catalyzed by heterogeneous Ag/Mo oxides

Complicated and expensive organic ligands are normally essential in fine chemical synthesis at preparative or industrial levels. The synthesis of fine chemicals by using heterogeneous catalyst systems without additive organic ligand is highly desirable but severely limited due to their poor generality and rigorous reaction conditions. Here, we show the results of carbon–nitrogen or carbon–carbon bond formation catalyzed by an Ag/Mo hybrid material with specific Ag₆Mo₁₀O₃₃ crystal structure. 48 nitrogen‐ or oxygen‐containing compounds, that is, amines, carboxamides, sulfonamides, and ketones, were successfully synthesized through a borrowing‐hydrogen mechanism. Up to 99 % isolated yields were obtained under relatively mild conditions without additive organic ligand. The catalytic process shows promise for the efficient and economic synthesis of amine, carboxamide, sulfonamide, and ketone derivatives because of the simplicity of the system and ease of operation.     

Metal–Organic Framework‐Templated Porous Carbon for Highly Efficient Catalysis: The Critical Role of Pyrrolic Nitrogen Species

Metal‐free catalysts are of great importance and alternative candidates to conventional metal‐based catalysts for many reactions. Herein, several types of metal–organic frameworks have been exploited as templates/precursors to afford porous carbon materials with various nitrogen dopant forms and contents, degrees of graphitization, porosities, and surface areas. Amongst these materials, the PCN‐224‐templated porous carbon material optimized by pyrolysis at 700 °C (denoted as PCN‐224‐700) is composed of amorphous carbon coated with well‐defined graphene layers, offering a high surface area, hierarchical pores, and high nitrogen content (mainly, pyrrolic nitrogen species). Remarkably, as a metal‐free catalyst, PCN‐224‐700 exhibits a low activation energy and superior activity to most metallic catalysts in the catalytic reduction of 4‐nitrophenol to 4‐aminophenol. Theoretical investigations suggest that the content and type of the nitrogen dopant play crucial roles in determining the catalytic performance and that the pyrrolic nitrogen species makes the dominant contribution to this activity, which explains the excellent efficiency of the PCN‐224‐700 catalyst well.