Institut Charles Gerhardt Montpellier

International audience

Despite the imminent commercial introduction of Li-ion batteries in electric drive vehicles and their proposed use as enablers of smart grids based on renewable energy technologies, an intensive quest for new electrode materials that bring about improvements in energy density, cycle life, cost, and safety is still underway. This Progress Report highlights the recent developments and the future prospects of the use of phases that react through conversion reactions as both positive and negative electrode materials in Li-ion batteries. By moving beyond classical intercalation reactions, a variety of low cost compounds with gravimetric specific capacities that are two-to-five times larger than those attained with currently used materials, such as graphite and LiCoO(2), can be achieved. Nonetheless, several factors currently handicap the applicability of electrode materials entailing conversion reactions. These factors, together with the scientific breakthroughs that are necessary to fully assess the practicality of this concept, are reviewed in this report.

Flexible nanoporous chromium or iron terephtalates (BDC) MIL-53(Cr, Fe) or M(OH)[BDC] have been used as matrices for the adsorption and in vitro drug delivery of Ibuprofen (or alpha- p-isobutylphenylpropionic acid). Both MIL-53(Cr) and MIL-53(Fe) solids adsorb around 20 wt % of Ibuprofen (Ibuprofen/dehydrated MIL-53 molar ratio = 0.22(1)), indicating that the amount of inserted drug does not depend on the metal (Cr, Fe) constitutive of the hybrid framework. Structural and spectroscopic characterizations are provided for the solid filled with Ibuprofen. In each case, the very slow and complete delivery of Ibuprofen was achieved under physiological conditions after 3 weeks with a predictable zero-order kinetics, which highlights the unique properties of flexible hybrid solids for adapting their pore opening to optimize the drug-matrix interactions.

Copper-catalyzed Ullmann condensations are key reactions for the formation of carbon-heteroatom and carbon-carbon bonds in organic synthesis. These reactions can lead to structural moieties that are prevalent in building blocks of active molecules in the life sciences and in many material precursors. An increasing number of publications have appeared concerning Ullmann-type intermolecular reactions for the coupling of aryl and vinyl halides with N, O, and C nucleophiles, and this Minireview highlights recent and major developments in this topic since 2004.

Titanium is a very attractive candidate for MOFs due to its low toxicity, redox activity, and photocatalytic properties. We present here MIL-125, the first example of a highly porous and crystalline titanium(IV) dicarboxylate (MIL stands for Materials of Institut Lavoisier) with a high thermal stability and photochemical properties. Its structure is built up from a pseudo cubic arrangement of octameric wheels, built up from edge- or corner-sharing titanium octahedra, and terephthalate dianions leading to a three-dimensional periodic array of two types of hybrid cages with accessible pore diameters of 6.13 and 12.55 A. X-ray thermodiffractometry and thermal analysis show that MIL-125 is stable up to 360 degrees C under air atmosphere while nitrogen sorption analysis indicates a surface area (BET) of 1550 m(2) x g(-1). Moreover, under nitrogen and alcohol adsorption, MIL-125 exhibits a photochromic behavior associated with the formation of stable mixed valence titanium-oxo compounds. The titanium oxo cluster are back oxidized in the presence of oxygen. This photochemical phenomenon is analyzed through the combined use of Electron Spin Resonance (ESR) and UV-visible absorption spectroscopies. The photogenerated electrons are trapped as Ti(III) centers, while a concomitant oxidation of the adsorbed alcohol molecules occurs. This new microporous hybrid is a very promising candidate for applications in smart photonic devices, sensors, and catalysis.

In this tutorial review we discuss the latest developments in ultra-microporous MOF adsorbents and their use as separating agents<italic>via</italic>thermodynamics and/or kinetics and molecular sieving.

International audience

The current interest in ionic liquids (ILs) is motivated by some unique properties, such as negligible vapour pressure, thermal stability and non-flammability, combined with high ionic conductivity and wide electrochemical stability window. However, for material applications, there is a challenging need for immobilizing ILs in solid devices, while keeping their specific properties. In this critical review, ionogels are presented as a new class of hybrid materials, in which the properties of the IL are hybridized with those of another component, which may be organic (low molecular weight gelator, (bio)polymer), inorganic (e.g. carbon nanotubes, silica etc.) or hybrid organic-inorganic (e.g. polymer and inorganic fillers). Actually, ILs act as structuring media during the formation of inorganic ionogels, their intrinsic organization and physicochemical properties influencing the building of the solid host network. Conversely, some effects of confinement can modify some properties of the guest IL, even though liquid-like dynamics and ion mobility are preserved. Ionogels, which keep the main properties of ILs except outflow, while allowing easy shaping, considerably enlarge the array of applications of ILs. Thus, they form a promising family of solid electrolyte membranes, which gives access to all-solid devices, a topical industrial challenge in domains such as lithium batteries, fuel cells and dye-sensitized solar cells. Replacing conventional media, organic solvents in lithium batteries or water in proton-exchange-membrane fuel cells (PEMFC), by low-vapour-pressure and non flammable ILs presents major advantages such as improved safety and a higher operating temperature range. Implementation of ILs in separation techniques, where they benefit from huge advantages as well, relies again on the development of supported IL membranes such as ionogels. Moreover, functionalization of ionogels can be achieved both by incorporation of organic functions in the solid matrix, and by encapsulation of molecular species (from metal complexes to enzymes) in the immobilized IL phase, which opens new routes for designing advanced materials, especially (bio)catalytic membranes, sensors and drug release systems (194 references).

Carbon-based structures are the most versatile materials used in the modern field of renewable energy (i.e., in both generation and storage) and environmental science (e.g., purification/remediation). However, there is a need and indeed a desire to develop increasingly more sustainable variants of classical carbon materials (e.g., activated carbons, carbon nanotubes, carbon aerogels, etc.), particularly when the whole life cycle is considered (i.e., from precursor "cradle" to "green" manufacturing and the product end-of-life "grave"). In this regard, and perhaps mimicking in some respects the natural carbon cycles/production, utilization of natural, abundant and more renewable precursors, coupled with simpler, lower energy synthetic processes which can contribute in part to the reduction in greenhouse gas emissions or the use of toxic elements, can be considered as crucial parameters in the development of sustainable materials manufacturing. Therefore, the synthesis and application of sustainable carbon materials are receiving increasing levels of interest, particularly as application benefits in the context of future energy/chemical industry are becoming recognized. This review will introduce to the reader the most recent and important progress regarding the production of sustainable carbon materials, whilst also highlighting their application in important environmental and energy related fields.

International audience

International audience

The present review offers an overview of nonclassical (e.g., with no pre- or in situ activation of a carboxylic acid partner) approaches for the construction of amide bonds. The review aims to comprehensively discuss relevant work, which was mainly done in the field in the last 20 years. Organization of the data follows a subdivision according to substrate classes: catalytic direct formation of amides from carboxylic and amines ( section 2 ); the use of carboxylic acid surrogates ( section 3 ); and the use of amine surrogates ( section 4 ). The ligation strategies (NCL, Staudinger, KAHA, KATs, etc.) that could involve both carboxylic acid and amine surrogates are treated separately in section 5 .

Pure micrometric antimony can be successfully used as negative electrode material in Na-ion batteries, sustaining a capacity close to 600 mAh g(-1) at a high rate with a Coulombic efficiency of 99 over 160 cycles, an extremely high capacity compared to any other compound tested against both Li and Na. The reaction mechanism with Na does not simply go through the alloying mechanism observed for Li where the intermediate species are those expected from the phase diagram. In the case of Na, the intermediate phases are mostly amorphous and could not be precisely identified. Surprisingly, we evidenced that a competition takes place at the end of the discharge of the Sb/Na cell between the formation of the hexagonal and the cubic polymorphs of Na(3)Sb, the last being described in the literature as unstable at atmospheric pressure and only synthesized under high pressure (1-9 GPa). In addition, fluoroethylene carbonate added to the electrolyte combined with an appropriate electrode formulation based on carboxymethyl cellulose, carbon black, and vapor ground carbon fibers seems to be determinant in the excellent performances of this material.

Metal–organic frameworks (MOFs) have received huge attention in the last years as promising porous materials with unrivalled degree of tunability for a wide range of applications including gas storage or separation, catalysis, drug delivery and imaging. The present review appraises the application of MOFs in the field of electrochemistry. From materials for rechargeable batteries, supercapacitors and fuel cells to electrocatalysis or corrosion inhibition, MOFs or MOF-derived materials are gaining momentum in this field. For real breakthroughs, combining their electrochemical properties with appropriate electronic and ionic conductivity will be required.

The use of vanillin as a building block for the chemical industry is discussed in this article. Vanillin is currently one of the only molecular phenolic compounds manufactured on an industrial scale from biomass. It has thus the potential to become a key-intermediate for the synthesis of bio-based polymers, for which aromatic monomers are needed to reach good thermo-mechanical properties. After a first part dedicated to the current sourcing of vanillin, this article focuses on the alkaline oxidation lignin-to-vanillin process, reporting advantages and limits, discusses the various postdepolymerization methods for product isolation and finally examines the outlook for the wider use of vanillin as a key building block for the chemical industry.

Lithium-ion (Li-ion) batteries that rely on cationic redox reactions are the primary energy source for portable electronics. One pathway toward greater energy density is through the use of Li-rich layered oxides. The capacity of this class of materials (>270 milliampere hours per gram) has been shown to be nested in anionic redox reactions, which are thought to form peroxo-like species. However, the oxygen-oxygen (O-O) bonding pattern has not been observed in previous studies, nor has there been a satisfactory explanation for the irreversible changes that occur during first delithiation. By using Li2IrO3 as a model compound, we visualize the O-O dimers via transmission electron microscopy and neutron diffraction. Our findings establish the fundamental relation between the anionic redox process and the evolution of the O-O bonding in layered oxides.

Nitrogen-doped carbon materials featuring atomically dispersed metal cations (M–N–C) are an emerging family of materials with potential applications for electrocatalysis. The electrocatalytic activity of M–N–C materials toward four-electron oxygen reduction reaction (ORR) to H2O is a mainstream line of research for replacing platinum-group-metal-based catalysts at the cathode of fuel cells. However, fundamental and practical aspects of their electrocatalytic activity toward two-electron ORR to H2O2, a future green “dream” process for chemical industry, remain poorly understood. Here we combined computational and experimental efforts to uncover the trends in electrochemical H2O2 production over a series of M–N–C materials (M = Mn, Fe, Co, Ni, and Cu) exclusively comprising atomically dispersed M–Nx sites from molecular first-principles to bench-scale electrolyzers operating at industrial current density. We investigated the effect of the nature of a 3d metal within a series of M–N–C catalysts on the electrocatalytic activity/selectivity for ORR (H2O2 and H2O products) and H2O2 reduction reaction (H2O2RR). Co–N–C catalyst was uncovered with outstanding H2O2 productivity considering its high ORR activity, highest H2O2 selectivity, and lowest H2O2RR activity. The activity–selectivity trend over M–N–C materials was further analyzed by density functional theory, providing molecular-scale understandings of experimental volcano trends for four- and two-electron ORR. The predicted binding energy of HO* intermediate over Co–N–C catalyst is located near the top of the volcano accounting for favorable two-electron ORR. The industrial H2O2 productivity over Co–N–C catalyst was demonstrated in a microflow cell, exhibiting an unprecedented production rate of more than 4 mol peroxide gcatalyst–1 h–1 at a current density of 50 mA cm–2.

International audience

Guest editors Guillaume Maurin, Christian Serre, Andrew Cooper and Gérard Férey introduce the Metal–Organic Frameworks and Porous Polymers – Current and Future Challenges issue of <italic>Chemical Society Reviews</italic>.

Amines are key intermediates in the chemical industry due to their nucleophilic characteristic which confers a high reactivity to them. Thus, they are key monomers for the synthesis of polyamides, polyureas, polyepoxydes, which are all of growing interest in automotive, aerospace, building, or health applications. Despite a growing interest for biobased monomers and polymers, and particularly polyamides, it should be noticed that very few natural amines are available. Actually, there is only chitosan and poly(lysine). In this review we present both fundamental and applied research on the synthesis of biobased primary and secondary amines with current available biobased resources. Their use is described as a building block for material chemistry. Hence, we first recall some background on the synthesis of amines, including the reactivity of amines. Second we focus on the synthesis of biobased amines from all sorts of biomass, from carbohydrate, terpenes, or oleochemical sources. Third, because they need optimization and technological developments, we discuss some examples of their use for the creation of biobased polymers. We conclude with the future of the synthesis of biobased amines and their use in different applications.