Overview
This research theme focuses on the understanding of structure and dynamics in "fluid" media and materials that fall within the field of sustainable chemistry and energy. It is based on national and international multidisciplinary collaborations and original instrumental developments in IR/Raman/Neutron spectroscopy ensuring the implementation of samples in "extreme" conditions, in particular for in situ and in operando studies.
Supercritical CO2 as a solvent for the impregnation of active ingredients in polymers and as a reagent for the organocatalyzed synthesis of cyclic carbonate
In the context of sustainable chemistry, the use of carbon dioxide both as a substitute for organic solvents and as a source of carbon C1 has received particular attention in recent years. Thus, in the context of collaborations with the University of Liege (Belgium) and the University of Aix-Marseille, we have shown the interest of using supercritical CO2 as a solvent to impregnate active ingredients in surgical implants (suture threads, intraocular implants). In particular, we determined by in-situ IR microscopy on commercial implants the solubility of CO2 in the implant and its resulting volume expansion (swelling). On the other hand, the use of CO2 as a raw material for the synthesis of renewable chemicals is a very promising route. Since CO2 is a thermodynamically stable molecule, the use of catalysts is therefore mandatory to activate and facilitate CO2/substrate coupling reactions selectively under mild conditions. Over the past five years, the main objective of our work carried out in collaboration with the THEO group of the ISM and the University of Liege has been the development of new organocatalytic platforms for the coupling of CO2 with various substrates such as epoxides, oxetanes, propargyl alcohols and diols for the synthesis of cyclic carbonates. In particular, in situ kinetic studies by IR/Raman spectroscopy correlated with DFT calculations were carried out in order to identify at the molecular level the catalytic mechanisms and reactant/catalyst interactions that govern the observed kinetics, yields and selectivities.
Energy storage and production
To meet environmental challenges and cope with growing energy consumption, it is essential to develop more efficient and environmentally friendly energy production and storage systems. With this in mind, an optimization of the materials used in fuel cells, photovoltaic cells, batteries or supercapacitors, is essential. Several studies have been conducted on these materials within GSM, in collaboration with ICMCB (Pessac), IMS (Pessac), CEA LETI (Grenoble), LRCS (Amiens), the Center for Structural Chemistry of the University of Lisbon (Portugal) and the University of Waterloo (Canada). For example, oxides, sulphides and phosphates of transition metals, which could be used as electrode materials, were studied. As a probe of local symmetry, IR and Raman vibrational spectroscopies were combined to perform a detailed analysis of the structure of these materials, to understand the influence of chemical composition and synthesis conditions, and to track structural changes during electrochemical processes. On the other hand, we studied the properties of new transparent electrodes prepared from random conductive networks of silver nanowires, deposited on a flexible transparent polymer film. In order to extend the life of these devices, we analyzed the passivation of silver nanowires prepared in solution, using organic molecules slowing their oxidation. A surface enhanced Raman scattering experiment was designed to study in situ the adsorption of a passivating molecule on the surface of silver wires. Finally, hydrate clathrates are the subject of much research for targeted technologies (desalination, gas separation/storage, etc.). Chemical additives play a major role in modulating the performance of these applications. Within the group, we develop original research through the use of acid additives (e.g. HClO4, HPF6) to modify the physico-chemical properties of hydrates (inhibition/promotion kinetic or thermodynamic, ion transport, etc.). In addition to the study of their structural and dynamic properties by neutron scattering and MD simulations, we have highlighted an improvement (by an order of magnitude) in the kinetics of hydrogen hydrate formation by in situ Raman microimaging in real time, related to the flexibilization of clathrate cages by adding strong acids in low concentration. In addition, we carried out a complete study ranging from the understanding of the "super-protonic" conduction mechanisms of strong acid clathrates to the realization of a fuel cell pilot using them as an electrolyte (operating between +/-30° C and formed at 85% water.
Ionic liquids for innovative and sustainable chemistry
Ionic liquids (ILs) are a class of solvents used in industrial processes with high added value (electrodeposition processes, pharmaceutical applications, etc.). In collaborations with the University of Aveiro and the University of Lisbon (Portugal), we conducted a series of studies based on a multi-technical experimental approach (NMR spectroscopy, IR absorption and Raman scattering) combined with modeling by ab initio or DFT calculations. These studies have led to a better understanding of the structural organization within ILs solutions and in particular, within electrolytes of metal salts of copper and silver dissolved in [EMI][EtSO4] and [EMI][TFSI] used for the electrodeposition of films on integrated circuits in microelectronics. On the other hand, we have shown that the dissolution of an alcohol having a very exacerbated acidic character such as perfluoro-ter-butanol (CF3)3OH (pKa~5.4) in [Bmim][Ac] induces a spontaneous reaction by the exchange of the acid proton of the alcohol with the acetate to form a perfluoro-ter-butoxide anion [Pftb] giving rise to a new IL, the [BMI][Pftb]. This method of preparation is a simple and economical example of the synthesis of new ILs.
Encapsulation of toxic metals (Cs, Tl) by water-soluble cryptophanes
For several years, we have been developing, in collaboration with T. Brotin of the Ecole Normale Supérieure de Lyon, chiral molecular cages (cryptophanes) with a lipophilic cavity that allows them to accommodate guest species of varying size and nature. In addition to their chiroptic properties, we studied the complexation properties of these molecules with toxic metals such as cesium and thallium. Finally, these molecules were grafted onto flat surfaces and superparamagnetic nanoparticles to form nanomaterials capable of selectively extracting cesium and thallium from a solution containing other ionic species.
Ongoing projects
The research perspectives that we plan to develop in the long term focus on understanding molecular organization, solvation phenomena and reactivity within materials and "fluid" media that fall within the field of sustainable chemistry and energy. In particular, we plan to carry out work on the valorization of CO2 as a solvent and as a reagent for the (photo) catalytic synthesis of molecules and / or sustainable polymer materials, the storage of hydrogen in clathrates / hydrates, the development of new cryptophanes for the encapsulation of toxic metals, the development of new materials of efficient organic electrodes, from biomass, for the development of renewable batteries, and the optimization of new materials used in fuel cells and photovoltaic cells (perovskite). These studies will be carried out by combining spectroscopic experiments (IR, Raman, PM-IRRAS, VCD, ROA, Neutrons) and molecular models (ab-initio, DFT and Molecular Dynamics) already well mastered in the group. In addition, in order to achieve a better understanding at the molecular level of the physical chemistry of the systems studied and to correlate their performance to their structural properties, methodological developments will be carried out at the experimental (multimodal spectroscopy in situ and in operando) and theoretical level, in particular to describe molecules in excited electronic states.