Carbon Heteroatom Research Articles

B, N Codoped Defective Reduced Graphene Oxide as a Highly Efficient Frustrated Lewis Pairs Catalyst for the Selective Hydrogenation of α,β-Unsaturated Aldehydes to Unsaturated Alcohols.

The development of all-solid-state frustrated Lewis pairs (FLPs) metal-free hydrogenation catalysts with excellent activity and stability remains a significant challenge. In this work, B, N codoped FLPs catalysts (De-rGO-NxBy) were prepared by the strategy of fabricating carbon defects and heteroatom doping on the surface of reduced graphene oxide and applied in the selective hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols. It was found that electron-rich pyridine-N (Lewis base) and adjacent electron-deficient B-N (Lewis acid) sites could be constructed on the surface of reduced graphene oxide using dicyandiamide and metaboric acid as N and B sources, thus forming FLPs sites. More importantly, the constructed carbon defects could facilitate the formation of pyridinic-N/B-N FLPs sites, thereby improving the catalytic hydrogenation activity and the selectivity to unsaturated alcohols. Furthermore, in situ DRIFTS and DFT calculations show that the pyridinic-N/B-N FLPs sites can efficiently activate the C═O of aldehydes and H2 molecules with only 0.53 eV dissociation energy of the H-H bond. Also, the catalyst presents excellent catalytic performance in the transfer hydrogenation reactions with cyclohexanol and its derivatives as hydrogen sources. This study provides new ideas for the design and preparation of all-solid-state FLPs metal-free catalysts and promotes the green synthesis of unsaturated alcohols.

Electrosynthesis for the Invention of New Organic Reactions

Electrosynthesis has emerged as a versatile and powerful tool in organic chemistry, facilitating the discovery and advancement of novel organic reactions. By harnessing electricity, this cutting-edge method generates reactive intermediates, driving chemical transformations to produce intricate organic compounds. This talk will present significant breakthroughs from our research group, showcasing the innovative use of electrochemistry in uncovering transformative reactions. Highlighted discoveries include (a) a site-selective arene C–H functionalization reaction, utilizing nitrogen radical intermediates generated through anodic or cathodic processes to yield aryl amines; and (b) an electrochemical strategy for generating carbon-based radicals from organoboron reagents, utilized in constructing diverse carbon–carbon and carbon–heteroatom bonds. The presentation will delve into the discovery process, development, scope, and mechanism of these reactions.

Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts.

Diaryliodonium salts have become widely recognized as arylating agents in the last two decades. Both, symmetrical and unsymmetrical forms of these salts serve as effective electrophilic arylating reagents in various organic syntheses. The use of diaryliodoniums in C-C and carbon-heteroatom bond formations, particularly under metal-free conditions, has further enhanced the popularity of these reagents. In this review, we concentrate on various arylation reactions involving carbon and other heteroatoms, encompassing rearrangement reactions in the absence of any metal catalyst, and summarize advancements made in the last five years.

Photoinduced Radical Borylation of Robust Carbon–Heteroatom Bonds

AbstractPhotoinduced borylation has emerged as a valuable strategy for synthesizing arylboronic esters. However, photochemical transformations involving inert bonds such as C(sp2)−F bonds are still challenging. Herein, we report a straightforward and operationally simple method for the activation of various inert carbon–heteroatom bonds, enabling the synthesis of diverse arylboronic esters without the need for transition metals or catalysts. Mechanistic investigations reveal that the deprotonation of DMSO plays a pivotal role in the reaction, and the excited DMSO anion can undergo electron transfer to the aryl substrates activated by anionic sp2–sp3 diboron compounds, i. e., [FB2pin2]−, thereby facilitating the cleavage of carbon–heteroatom bonds. The reaction allows the conversion of diverse Caryl–hetero bonds in batch and flow reactors into the corresponding arylboronic esters. The products can be used in a subsequent Suzuki‐Miyaura cross‐coupling without isolation.

Carbonylation Reactions at Carbon-Centered Radicals with an Adjacent Heteroatom.

Heteroatoms are essential to living organisms and present in almost all molecules with medicinal usage. The catalytic functionalization at the carbon-centered radical with an adjacent heteroatom provides an effective way to value added moiety while retaining the unique physicochemical and pharmacological properties of heteroatoms, which can promote the development of pharmaceutical and fine chemical production. Carbonylative transformation was discovered nearly a century ago which is an efficient method for the synthesis of carbonyl-containing molecules with potent applications in both industry and academia. Despite numerous advances in new reaction development, carbonylative transformation involving adjacent heteroatom carbon radical remain a subject that deserves to be discussed. In this minireview, we systematically summarized and discussed the recent advances in carbonylative transformations involving carbon-centered radicals with an adjacent heteroatom, including oxygen (O), nitrogen (N), phosphorus (P), silicon (Si), sulfur (S), boron (B), fluorine (F), and chlorine (Cl). The related reaction mechanism was also discussed.

Carbonylation Reactions at Carbon‐Centered Radicals with an Adjacent Heteroatom

AbstractHeteroatoms are essential to living organisms and present in almost all molecules with medicinal usage. The catalytic functionalization at the carbon‐centered radical with an adjacent heteroatom provides an effective way to value added moiety while retaining the unique physicochemical and pharmacological properties of heteroatoms, which can promote the development of pharmaceutical and fine chemical production. Carbonylative transformation was discovered nearly a century ago which is an efficient method for the synthesis of carbonyl‐containing molecules with potent applications in both industry and academia. Despite numerous advances in new reaction development, carbonylative transformation involving adjacent heteroatom carbon radical remain a subject that deserves to be discussed. In this minireview, we systematically summarized and discussed the recent advances in carbonylative transformations involving carbon‐centered radicals with an adjacent heteroatom, including oxygen (O), nitrogen (N), phosphorus (P), silicon (Si), sulfur (S), boron (B), fluorine (F), and chlorine (Cl). The related reaction mechanism was also discussed.

Co2P/CoP embedded in N, P, S triply-doped hollow carbon towards enhanced oxygen electrocatalysis

Simultaneously dispersing phosphide crystallites and multiple heteroatoms in hollow carbon is a significant yet challenging task for achieving high-performance oxygen electrocatalysts of zinc-air batteries. Herein, a simple wrapping-pyrolysis strategy is proposed to prepare Co2P/CoP embedded in N, P, S triply-doped hollow carbon (Co2P/CoP@NPS-HC). Co2P/CoP@NPS-HC composite features hollow polyhedral structure populated with numerous catalytically active Co2P/CoP nanoparticles and N, P, S heteroatoms. This optimized catalyst exhibits excellent activity for oxygen reduction reaction, with a half-wave potential of 0.82 V vs. RHE, and impressive enhancement for oxygen evolution reaction, indicated by an overpotential of 400 mV at 10 mA cm−2. Moreover, Co2P/CoP@NPS-HC catalyst exhibits greater durability and superior methanol tolerance compared to commercial Pt/C. The excellent bifunctional electrocatalytic performance of Co2P/CoP@NPS-HC catalyst is attributed to the synergistic effect of uniformly dispersed Co2P/CoP nanoparticles and N, P, S triply-doped hollow carbon structure. The former provides abundant catalytically active sites, while the latter offers a high accessible specific surface area, as well as enhances catalytic activity and electronic conductivity due to its altered charge distribution.

Iodine‐Promoted Cascade Redox Cyclization to Access 2‐Arylbenzothiazoles Using Elemental Sulfur

ABSTRACTA straightforward and efficient method has been developed to access a variety of benzothiazole derivatives via cascade reductive annulation. Iodine mediated, one‐pot three‐component reaction of o‐chloronitroarenes, aryl aldehydes, and elemental sulfur effectively produce benzothiazoles. Moreover, the metal‐free strategy allows the facile synthesis of diverse 2‐substituted benzothiazoles through multiple carbon–heteroatom bonds in good yields. The present protocol features a greener approach, readily accessible reagents, broad substrate scope, high product yields, and operational simplicity.

NiCo layered double hydroxides/carbon dots composites with S-doing for high-performance asymmetric supercapacitors

The pursuit of high-performance electrode materials for supercapacitors has led to the exploration of transition metal layered double hydroxides (LDH), which boast an impressive theoretical specific capacitance. However, their intrinsic limitations, such as poor electronic conductivity and slow diffusion kinetics, have posed significant challenges for their practical implementation. In this work, a NiCo LDH/carbon dots (CDs) composite with S-doping has been meticulously designed to overcome the aforementioned limitations through a synergistic combination of heteroatom doping and carbon incorporation. Utilizing a one-pot hydrothermal method, the composite electrode for the application of asymmetric supercapacitors have been in-situ growth on Ni foam substrate, which not only serves as a robust support but also contributes to the formation of NiCo LDH by providing a uniform Ni source, thereby ensuring strong adhesion and structural integrity. The morphology and microstructures of composites could be finely modulated by adjusting CDs amount. With moderate CDs contents, the optimum electrode S-LDH/CDs-2 exhibits distinctive 3D needle-like spherical morphology, coupled with the ample space for ion diffusion. Consequently, the electrode demonstrates outstanding electrochemical performance, featuring a high areal capacitance of 5157 mF cm−2 at a current density of 2 mA cm−2. Additionally, it exhibits noteworthy rate performance and maintains excellent cycling stability. Integrating the innovative electrode into asymmetric supercapacitors configuration, superior energy density (0.24–0.45 mWh cm−2) and power density (4–20 mW cm−2) as well as good stability have been achieved for the S-LDH/CDs-2//AC device. These results indicate that S-doped NiCo LDH/CDs composite electrode has the desirable potential to be a candidate for energy storage devices.

Electrochemical synthesis of heterocyclic compounds via carbon–heteroatom bond formation: direct and indirect electrolysis

Abstract Electrochemical organic synthesis has attracted attention as an environmentally friendly method for constructing heterocyclic compounds via carbon–heteroatom bond formation. Herein, we describe the representative examples of electrochemical reactions to produce heterocycles and discuss them according to whether they involve direct or indirect electrolysis.

Microbial regulation on refractory dissolved organic matter in inland waters

The production of refractory dissolved organic matter (RDOM) is complex and closely related to microbial consortia in aquatic ecosystems; however, it is still unclear how microorganisms regulate the production of RDOM and its molecular composition in inland waters. Therefore, we conducted a large-scale survey of inland waters and analyzed the optical and mass spectrometric characteristics of DOM, the microbial community and functional genes, as well as related environmental parameters, to understand the abovementioned issues. Here, the RDOM production was found mainly regulated by microbial (e.g., phylogeny and community assembly) rather than other environmental factors in inland waters. Biostatistical analyses and carbon isotopic evidence indicated that the successive microbial processing from labile DOM to RDOM (i.e., carboxyl-rich alicyclic molecules, CRAMs) was widely present in inland waters, involving the microbially mediated carbon skeleton turnover and heteroatom conversion. There was a significant empirical relationship between CRAMs and the ratio of Proteobacteria to Actinobacteria, highlighting the intraspecific interaction of bacteria more important than other microbial groups (i.e., archaea, eukaryotes, and fungi) for the RDOM production. This study demonstrated a fundamental role of microbial regulation in RDOM production within the inland waters, thereby facilitating future estimation of carbon sequestration potential in inland aquatic ecosystems.

MOF-derived high-density carbon nanotubes “tentacle” with boosting electrocatalytic activity for detecting ascorbic acid

Accurate detection of ascorbic acid (AA) plays a significant role in food and human physiological processes. Herein, a three-dimensional flexible leaf-like nitrogen-doped hierarchical carbon nanoarrays with high-density carbon nanotube “tentacle” architecture (NC/CNT-Co), which possesses high specific surface area, plenty of active defect sites, and various pore size distributions, was synthesized by the pyrolysis of zeolitic imidazolate framework (ZIF(Co)), while g-C3N4 acted as carbon source and heteroatom doping agent. Benefiting from its unique structure and surface properties, a selective and highly sensitive AA sensor was developed using this material. Compared to powder materials, NC/CNT-Co modified CF (CF@NC/CNT-Co) which don't be extra decorated, exhibits lower detection limit (1 μM), a wider linear range (20–1400 μM), and better stability, showing higher performance in electrocatalysis and detection of AA. Furthermore, CF@NC/CNT-Co also demonstrates high resistance to interference and fouling in AA detection. Particularly, the prepared CF@NC/CNT-Co electrode could determine AA in beverage samples with a recovery rate of 96.3–103.5 %. Therefore, the three-dimensional NC/CNT-Co hierarchical structure can be provided as an original electrode nanomaterial suitable for the selective and sensitive detection of AA, with a wide range of practical applications from food analysis to the pharmaceutical industry.

Overcoming metals redox rate limitations in spinel oxide-driven Fenton-like reactions via synergistic heteroatom doping and carbon anchoring for efficient micropollutant removal

The transition metals redox rate limitations of spinel oxides during Fenton-like reactions hinder its efficient and sustainable treatment of actual wastewater. Herein, we propose to optimize the electronic structure of Co-Mn spinel oxide (CM) via sulfur doping and carbon matrix anchoring synergistically, enhancing the radicals-nonradicals Fenton-like processes for efficient water decontamination. Activating peroxymonosulfate (PMS) with optimised spinel oxide (CMSAC) achieved near-complete removal of ofloxacin (10 mg/L) within 6 min, showing 8.4 times higher efficiency than CM group. Significantly higher yields of SO4·− and high-valent metal species in CMSAC/PMS system provided exceptional resistance to co-existing anions, enabling efficient removal of various emerging contaminants in high salinity leachate. Specifically, sulfur coordination and carbon anchoring-induced oxygen vacancy synergistically improved the electronic structure and electron transfer efficiency of CMSAC, thus forming highly reactive Co sites and significantly reducing the energy barrier for Co(IV)=O generation. The reductive sulfur species facilitated the conversion of Co(III) to Co(II), thereby maintaining the stability of the catalytic activity of CMSAC. This work developed a synergistic optimization strategy to overcome the metals redox rate limitations of spinel oxides in Fenton-like reactions, providing deep mechanistic insights for designing Fenton-like catalysts suitable for practical applications.

C–heteroatom coupling with electron-rich aryls enabled by nickel catalysis and light

Nickel photoredox catalysis has resulted in a rich development of transition-metal-catalysed transformations for carbon–heteroatom bond formation. By harnessing light energy, the transition metal can attain oxidation states that are difficult to achieve through thermal chemistry in a catalytic manifold. For example, nickel photoredox reactions have been reported for both the synthesis of anilines and aryl ethers from aryl(pseudo)halides. However, oxidative addition to simple nickel systems is often sluggish in the absence of special, electron-rich ligands, leading to catalyst decomposition. Electron-rich aryl electrophiles therefore currently fall outside the scope of many transformations in the field. Here we provide a conceptual solution to this problem and demonstrate nickel-catalysed C–heteroatom bond-forming reactions of arylthianthrenium salts, including amination, oxygenation, sulfuration and halogenation. Because the redox properties of arylthianthrenium salts are primarily dictated by the thianthrenium, oxidative addition of highly electron-rich aryl donors can be unlocked using simple NiCl2 under light irradiation to form the desired C‒heteroatom bonds.

Attenuating N-Oxyl Decomposition for Improved Hydrogen Atom Transfer Catalysts.

The design of N-oxyl hydrogen atom transfer catalysts has proven challenging to date. Previous efforts have focused on the functionalization of the archetype, phthalimide-N-oxyl. Driven in part by the limited options for modification of this structure, this strategy has provided only modest improvements in reactivity and/or solubility. Our previous mechanistic efforts suggested that while the electron-withdrawing carbonyls of the phthalimide are necessary to maximize the O-H bond dissociation enthalpy of the HAT product hydroxylamine and overall reaction thermodynamics, they undergo nucleophilic substitution leading to catalyst decomposition. In an attempt to minimize this vulnerability, we report the characterization of N-oxyl catalysts wherein the aryl ring in PINO is replaced with the combination of a substituted heteroatom and quaternary carbon. By rendering one carbonyl carbon less electrophilic and the other less sterically accessible, the corresponding N1-aryl-hydantoin-N3-oxyl radical showed significantly higher stability than PINO as well as a modest improvement in reactivity. This proof-of-principle in new scaffold design may accelerate future HAT catalyst discovery and development.

Attenuating N‐Oxyl Decomposition for Improved Hydrogen Atom Transfer Catalysts

AbstractThe design of N‐oxyl hydrogen atom transfer catalysts has proven challenging to date. Previous efforts have focused on the functionalization of the archetype, phthalimide‐N‐oxyl. Driven in part by the limited options for modification of this structure, this strategy has provided only modest improvements in reactivity and/or solubility. Our previous mechanistic efforts suggested that while the electron‐withdrawing carbonyls of the phthalimide are necessary to maximize the O−H bond dissociation enthalpy of the HAT product hydroxylamine and overall reaction thermodynamics, they undergo nucleophilic substitution leading to catalyst decomposition. In an attempt to minimize this vulnerability, we report the characterization of N‐oxyl catalysts wherein the aryl ring in PINO is replaced with the combination of a substituted heteroatom and quaternary carbon. By rendering one carbonyl carbon less electrophilic and the other less sterically accessible, the corresponding N1‐aryl‐hydantoin‐N3‐oxyl radical showed significantly higher stability than PINO as well as a modest improvement in reactivity. This proof‐of‐principle in new scaffold design may accelerate future HAT catalyst discovery and development.

Tunable electronic coupling of Fe-doped CoS2/reduced graphene oxide composites for boosting bifunctional water splitting activity

The electrochemical water splitting process is always restrained for its sluggish kinetics and high reaction energy barrier. Therefore, developing outstanding bifunctional catalysts to enhance the reaction kinetics and electron transfer efficiency of water splitting is crucial. In this work, we reported a bifunctional nanohybrid electrocatalyst consisting of Fe-doped CoS2 nanocage-decorated reduced graphene oxide (FCSRGO) with superior water splitting activity. The Fe doping adjusts the density of state (DOS) to increase the conductivity and decreases the adsorption free energy of intermediates, contributing to optimized catalytic activity. Furthermore, the incorporation of RGO reduces the agglomeration of CoS2 and improves the conductivity, thereby amplifying the charge/species transfer efficiency. By optimizing the amount of RGO, FCSRGO shows exceptional electrocatalytic performance, achieving a benchmark current density of 10 mA·cm−2 at remarkably low overpotentials (ƞ10) of 107 mV and 239 mV in 1 M KOH solution for HER and OER, respectively. Moreover, the nanohybrid exhibits remarkable stability with the current density retention of 89.8% for HER and 85.8% for OER after 36000 s test. This work highlights the creating of high-performance electrocatalysts for efficient and sustainable hydrogen and oxygen evolution through heteroatom doping and carbon incorporation.

Copper-Bisbenzimidazole Complexes as Biomimetic Catalysts in Organic Transformations

Abstract: Copper complexes have biological applications as well as catalytic importance in performing organic reactions. Besides finding utilities in metalloproteins, enzymes, or molecular magnetism, they have been used extensively as catalysts in the formation ofcarbon–carbon or carbon– heteroatom bonds, in addition to many other reactions. This has been achieved by the rational selection of the organic ligands with suitable coordination sites for attaining ideal geometries. The binding of one such organic ligand, bisbenzimidazole, with copper results in complexes with varied shapes, structures, and activities, enhancing their catalytic potential and hence useful applications. This review describes the catalytic applications of bisbenzimidazole based copper (II)/(I) complexes in various useful organic transformations. It also provides an in-depth knowledge of the mechanistic pathways of the transformations involving copper complexes and their multipurpose utility as catalysts, which may help in the development of improved copper catalysts for the future.

Coupling of Heteroatom Dopants and Intrinsic Carbon Defects for High‐Efficiency Electrocatalytic Oxygen Reduction

AbstractDefective engineering of carbon, including introduction of heteroatom dopants and creation of intrinsic carbon defects, to alter the surface electronic/spin state of the carbon matrix has become a vital research area of carbon‐based catalysts toward oxygen reduction reaction (ORR). When the heteroatom dopants and carbon intrinsic defects in the carbon matrix are spatially close enough, they could couple each other and synergistically endow the active centers with special electronic structures that might greatly enhance the ORR catalytic activities of the carbon‐based catalysts. In this concept, we propose a conceptual idea of coupling sites composed of heteroatom dopants and intrinsic carbon defects, systematically summarize the types of the coupling sites and their synergistic mechanisms for catalyzing the ORR, and present feasible ideas and major challenges for efficient construction and verification of the coupling sites. This concept might be enlightening for in‐depth studies on the design, construction, and understanding the structure‐activity relationship of high‐efficiency active sites in the carbon‐based catalysts.

Review of carbon-based catalysts for electrochemical nitrate reduction and green ammonia synthesis

This work aims to review the latest developments in carbon-based electrocatalysts applied in electrocatalytic nitrate reduction, including pure carbon materials, heteroatom doping or metal-bonding catalysts, and carbon substrate-supported composites.