Most cited article - PubMed ID 26263147
Reactivity of Fluorographene: A Facile Way toward Graphene Derivatives
Climate change and the depletion of fossil fuels increase the demand for sustainable energy. Biodiesel synthesized using heterogeneous acid catalysts is a promising clean-energy carrier that supports a circular carbon economy. Herein, the efficient synthesis of biodiesel is reported using a reusable solid acid graphene catalyst functionalized with a natural aminosulfonic acid. Experimental and theoretical studies reveal the key role of functionalities that simultaneously contain amino and sulfonate groups, which impart superior acidity. Excellent activity and selectivity for oleic acid conversion to oleic acid methyl esters (a sustainable biofuel) are obtained, offering a strategy for achieving improved catalytic performance compared to earlier or benchmark catalysts in the field. Notably, the catalyst also effectively converts common vegetable oils into biodiesel via transesterification and facilitates carbohydrate dehydration to value-added chemicals, demonstrating broad applicability. Two additional variants of aminosulfonic acid-functionalized graphene show similar activity, confirming the crucial role of these functionalities in achieving high acidity and catalytic performance. The development of such potent, recyclable catalysts is crucial because acid catalysis is highly versatile, underpinning many biological and synthetic transformations.
- Keywords
- biodiesel, esterification, graphene catalysts, heterogeneous acid catalysts, solid acid catalysis, transesterification,
- Publication type
- Journal Article MeSH
To enhance the sustainability of nuclear energy and protect the environment, the efficient extraction of uranium from various water sources has emerged as an essential strategy for addressing the long-term challenges of nuclear waste management. In this study, we designed phosphoryl-functionalized graphene (PG) for efficient uranyl adsorption and synthesized the material from fluorinated graphene using phosphoryl ethanolamine under solvothermal conditions. The resultant PG features a unique 2D structure equipped with solvent-exposed phosphoryl groups, making it highly suitable for uranium adsorption in aqueous solutions. Notably, PG demonstrated a high sorption efficiency (∼77%) with rapid extraction capability (∼5 min) for U(VI) from aqueous media at pH 7, achieving an adsorption capacity of 316 mg U g-1. It also demonstrates good recyclability and stability even after 3 cycles and exhibits a significant seawater adsorption capacity of 117.8 mg U g-1. Both X-ray photoelectron spectroscopy analysis and molecular dynamics simulations revealed a preferential binding of uranyl ions to the phosphoryl groups of PG. This work paves the way for designing and developing functional graphene derivatives for efficient uranium extraction from various water resources, with promising potential for the recovery of other radioactive elements.
Single-atom catalysts (SACs) based on graphene derivatives are an emerging and growing class of materials functioning as two-dimensional (2D) metal-coordination scaffolds with intriguing properties. Recently, owing to the rich chemistry of fluorographene, new avenues have opened toward graphene derivatives with selective, spacer-free, and dense functionalization, acting as in-plane or out-of-plane metal coordination ligands. The particular structural features give rise to intriguing phenomena occurring between the coordinated metals and the graphene backbone. These include redox processes, charge transfer, emergence, and stabilization of rare or otherwise unstable metal valence states, as well as metal-support and metal-metal synergism. The vast potential of such systems has been demonstrated as enzyme mimics for cooperative mixed-valence SACs, ethanol fuel cells, and CO2 fixation; however, it is anticipated that their impact will further expand toward diverse fields, e.g., advanced organic transformations, electrochemical energy storage, and energy harvesting.
- Publication type
- Journal Article MeSH
- Review MeSH
Fluorographene has been recently shown to be a suitable platform for synthesizing numerous graphene derivatives with desired properties. In that respect, N-octylamine-modified fluorographenes with variable degrees of functionalization are studied and their nonlinear optical properties are assessed using 4 ns pulses. A very strong enhancement of the nonlinear optical response and a very efficient optical limiting action are observed, being strongly dependent on the degree of functionalization of fluorographene. The observed enhanced response is attributed to the increasing number of defects because of the incorporation of N-heteroatoms in the graphitic network upon functionalization with N-octylamine. The present work paves the way for the controlled covalent functionalization of graphene enabling a scalable access to a wide portfolio of graphene derivatives with custom-tailored properties.
- Keywords
- N-doped graphene, graphene functionalization, nonlinear optical response, optical limiting,
- Publication type
- Journal Article MeSH
Controllable synthesis of graphene derivatives with defined composition and properties represents the holy grail of graphene chemistry, especially in view of the low reactivity of graphene. Recent progress in fluorographene (FG) chemistry has opened up new routes for synthesizing a plethora of graphene derivatives with widely applicable properties, but they are often difficult to control. We explored nucleophilic substitution on FG combining density functional theory calculations with experiments to achieve accurate control over the functionalization process. In-depth analysis revealed the complexity of the reaction and identified basic rules for controlling the 2D chemistry. Their application, that is, choice of solvent and reaction time, enabled facile control over the reaction of FG with N-octylamine to form graphene derivatives with tailored content of the alkylamine functional group (2.5-7.5% N atomic content) and F atoms (31.5-3.5% F atomic content). This work substantially extends prospects for the controlled covalent functionalization of graphene.
- Publication type
- Journal Article MeSH
Preparation of graphene derivatives using fluorographene (FG) as a precursor has become a key strategy for the large-scale synthesis of new 2-D materials (e.g. graphene acid, cyanographene, allyl-graphene) with tailored physicochemical properties. However, to gain full control over the derivatization process, it is essential to understand the reaction mechanisms and accompanying processes that affect the composition and structure of the final products. Despite the strength of C-F bonds and high chemical stability of perfluorinated hydrocarbons, FG is surprisingly susceptible to reactions under ambient conditions. There is clear evidence that nucleophilic substitution on FG is accompanied by spontaneous defluorination, and solvent-induced defluorination can occur even in the absence of any nucleophilic agent. Here, we show that distributed radical centers (fluorine vacancies) on the FG surface need to be taken into account in order to rationalize the defluorination mechanism. Depending on the environment, these radical centers can react as electron acceptors, electrophilic sites and/or cause homolytic bond cleavages. We also propose a new radical mechanism of FG defluorination in the presence of N,N'-dimethylformamide (DMF) solvent. Spin-trap experiments as well as 19F NMR measurements unambiguously confirmed formation of N,N'-dimethylformyl radicals and also showed that N,N'-dimethylcarbamoyl fluoride plays a key role in the proposed mechanism. These findings imply that point defects in 2D materials should be considered as key factor determining their chemical properties and reactivity.
- Publication type
- Journal Article MeSH
Fluorographene, formally a two-dimensional stoichiometric graphene derivative, attracted remarkable attention of the scientific community due to its extraordinary physical and chemical properties. We overview the strategies for the preparation of fluorinated graphene derivatives, based on top-down and bottom-up approaches. The physical and chemical properties of fluorographene, which is considered as one of the thinnest insulators with a wide electronic band gap, are presented. Special attention is paid to the rapidly developing chemistry of fluorographene, which was advanced in the last few years. The unusually high reactivity of fluorographene, which can be chemically considered perfluorinated hydrocarbon, enables facile and scalable access to a wide portfolio of graphene derivatives, such as graphene acid, cyanographene and allyl-graphene. Finally, we summarize the so far reported applications of fluorographene and fluorinated graphenes, spanning from sensing and bioimaging to separation, electronics and energy technologies.
- Keywords
- Chemistry, Covalent functionalization, Fluorographene, Graphene derivatives,
- Publication type
- Journal Article MeSH
- Review MeSH
Efficient and selective methods for covalent derivatization of graphene are needed because they enable tuning of graphene's surface and electronic properties, thus expanding its application potential. However, existing approaches based mainly on chemistry of graphene and graphene oxide achieve only limited level of functionalization due to chemical inertness of the surface and nonselective simultaneous attachment of different functional groups, respectively. Here we present a conceptually different route based on synthesis of cyanographene via the controllable substitution and defluorination of fluorographene. The highly conductive and hydrophilic cyanographene allows exploiting the complex chemistry of -CN groups toward a broad scale of graphene derivatives with very high functionalization degree. The consequent hydrolysis of cyanographene results in graphene acid, a 2D carboxylic acid with pKa of 5.2, showing excellent biocompatibility, conductivity and dispersibility in water and 3D supramolecular assemblies after drying. Further, the carboxyl groups enable simple, tailored and widely accessible 2D chemistry onto graphene, as demonstrated via the covalent conjugation with a diamine, an aminothiol and an aminoalcohol. The developed methodology represents the most controllable, universal and easy to use approach toward a broad set of 2D materials through consequent chemistries on cyanographene and on the prepared carboxy-, amino-, sulphydryl-, and hydroxy- graphenes.
- Keywords
- 2D acid, fluorographene chemistry, graphene acid, graphene nitrile, nucleophilic substitution,
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Materials based on metallic elements that have d orbitals and exhibit room temperature magnetism have been known for centuries and applied in a huge range of technologies. Development of room temperature carbon magnets containing exclusively sp orbitals is viewed as great challenge in chemistry, physics, spintronics and materials science. Here we describe a series of room temperature organic magnets prepared by a simple and controllable route based on the substitution of fluorine atoms in fluorographene with hydroxyl groups. Depending on the chemical composition (an F/OH ratio) and sp3 coverage, these new graphene derivatives show room temperature antiferromagnetic ordering, which has never been observed for any sp-based materials. Such 2D magnets undergo a transition to a ferromagnetic state at low temperatures, showing an extraordinarily high magnetic moment. The developed theoretical model addresses the origin of the room temperature magnetism in terms of sp2-conjugated diradical motifs embedded in an sp3 matrix and superexchange interactions via -OH functionalization.
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
