Description du sujet de thèse

To start, we will benchmark available methods in term of cost and accuracy on model acido-basic reactions. Accurate methods as DFT usually rely on a less accurate description of the aqueous solvent (as continuum models or micro-solvation or QM/MM) while more approximate methods as DFTb or machine learning potentials would allow to reach more easily a fully explicit description of water, including possible deprotonation/protonation of water.
Once the methodology established, we will explore the glucose-fructose isomerization mechanism in basic conditions in homogeneous conditions in strong collaboration with the group of Pr. I. Delidovich, a renowned expert of this reaction. We will compare at least two scenarii: without and with a phosphate buffer. We will explore the reaction barriers and equilibria of each elementary step using well-tempered metadynamics. We will design a set of few collective variables to explore the ring opening/closing and the proton shifts. In particular, a collective variable will be designed to bias the reorganization of the solvation shell and facilitate the proton shuttling. Our main focus will be to understand the influence of the phosphate on the selectivity of the glucose-fructose isomerisation since other unwanted processes may occur as the formation of the 3-deoxyglucosone.
Then, we will explore the same reaction, but at the solid catalyst/water interface. Phosphate-based catalysts are currently synthesized, characterized and tested at IRCELyon. In collaboration with the group of A. Mesbah, we will design a surface model of the most promising catalyst. This will allow us to explore the reaction mechanism and identify the rate-limiting steps. Then, we will explore how substitution could favor the isomerization and limits side routes.

Contexte de travail

The ANR project BisoGlu focuses on fundamental understanding of the catalytic isomerization of D-glucose into D-fructose in the presence of bases aiming at a rational design of an efficient and inexpensive catalyst. The project considers catalysis in the presence of soluble and solid bases. A long-standing question on roles of specific and general base catalysis in the presence of various buffers will be addressed. Insight into mechanisms, reaction networks, and kinetics in the presence of promising solid catalysts, for instance, apatites, will be gained by the international consortium of BisoGlu (Dr. Irina Delidovich (TU Wien, Austria), Dr. C. Pinel,Dr A Mesbah, L. Djakovitch (IRCELyon, France), C. Michel and S.N. Steinmann (LCH, France)).

The PhD student will be enrolled at the ENs de Lyon and the Chemistry graduate scholl of Lyon. He/She will be working at the LCH.

The LCH is a joint research unit (UMR5182) supervised by the CNRS, the École Normale Supérieure de Lyon and the Université Claude Bernard Lyon 1.

The LCH develops interdisciplinary research projects at the frontier between biology, materials science and physics. It tackles both conceptual and fundamental multi-scale aspects, as well as problems that are more advanced in terms of applications, in relation to the properties of the systems studied.
The laboratory's staff cover a broad spectrum of expertise in synthetic chemistry (organic, inorganic, (nano)materials, shaping), characterisation and advanced spectroscopy, combined with strong expertise in molecular modelling (excited states, reactivity, liquids, etc.).