Thèse Catalyse Régénérative pour la Valorisation de Matières Premières Fluorées à l'Aide de la Lumière H/F

Université Paris-Saclay GS Chimie

Établissement : Université Paris-Saclay GS Chimie
École doctorale : Sciences Chimiques : Molécules, Matériaux, Instrumentation et Biosystèmes
Laboratoire de recherche : Biomolécules : conception, isolement, synthèse
Direction de la thèse : Emmanuel MAGNIER ORCID 0000000333923971
Début de la thèse : 2026-10-01
Date limite de candidature : 2026-03-22T23:59:59

Ce projet exploite la photocatalyse régénérative par la lumière visible pour transformer des matières premières fluorées problématiques pour l'environnement en molécules durables et non persistantes. Plus précisément, l'objectif de la présente proposition est d'utiliser un nouveau concept, récemment inventé dans le laboratoire de Padoue, un photocatalyseur régénératif (appelé Phoenix [réf. 5]) pour la valorisation des matières premières fluorées afin de préparer de nouvelles cibles monofluorées, difluorées ou pentafluorosulfanylées. À partir de matières premières fluorées bon marché, disponibles, mais bientôt interdites, nous allons chercher à produire des composés fluorés hautement fonctionnalisés et non persistants (non-PFAS) à l'aide d'un nouveau type de photocatalyseur. Ce dernier sera étudié en détail à Padoue, y compris les propriétés physico-chimiques de notre système.

The organic chemistry of fluorine has recently undergone spectacular developments. This can be explained by the unrivalled properties that fluorine atoms induce in the molecules that carry them. [ref 6] This has led to a huge number of applications in both materials science and life science. [ref 7] As a result, an exponential number of publications have been devoted to new fluorinated reagents and/or new synthesis methodologies related to this field. Notably, photoredox catalysis has become the method of choice for the generation of perfluorinated radicals under mild conditions, as well as for original transformations and the preparation of unknown molecules. [ref 8] After a very intense period of innovation towards highly fluorinated molecules, environmental constraints are encouraging chemists to innovate towards i) non-persistent fluorinated groups i.e. non PFAS, ii) new tools to introduce these emerging groups under mild and selective conditions.
The group of Pr. Dell'Amico recently discovered the peculiar behaviour of a purely organic catalyst. [ref 5] Upon light irradiation, it undergoes controlled disruption, substrate activation, and regeneration in an unconventional regenerative catalytic cycle (see attached scheme, part a). Upon simple visible-light irradiation (LED 400 nm), the molecule cleaves, generating two different species capable of simultaneously unlocking opposed yet productive highly oxidative and highly reductive manifolds under irradiation. This unconventional mechanism is allowed by the unique regenerative properties of a purely organic dimeric photocatalyst (see figure), which undergoes controlled C-C bond breaking upon light excitation, providing access to a highly reducing (- 3.4 V vs SCE) and a highly oxidizing (+ 2.3 V vs SCE) species. After the activation of two different redox-inert substrates under opposed cycles (a reduction and an oxidation), the different subunits recombine to regenerate the original molecule.
By pooling our expertise, we will be able to offer a solution for transforming perfluorinated compounds into less fluorinated products using catalysis and light. This approach has been partially validated by recent publications describing the total degradation of perfluorinated compounds by photoredox catalysis.[ref 10-11] Our more ambitious project is the control defluorination to prepare novel molecules with high added value.

The two main objectives of this research program are (see attached scheme):
1) the reduction of SF6 for the generation of the SF5 radical and its incorporation into organic scaffolds
2) the generation of difluoromethyl and monofluoromethyl radical by a reductive-defluorinative sequence starting from trifluoroacetic acid derivatives.
In both cases, we are using feedstock compounds, available at low cost and in large quantities, but which are harmful to the environment. Our goal is to find a solution to the problem of converting these products into derivatives that do not have these disadvantages and can be use as fluorinated building blocks to the construction of biorelevant targets. The approach we plan to develop is also respectful of the environment as it will employ a regenerative photocatalyst system - a light-driven catalyst that regenerates itself during the reaction.

The research relies on the strong complementarity between the Versailles and Padua teams, combining expertise in synthetic fluorine chemistry, photochemistry, spectroscopy, and theory. The French partner will focus on the design and development of new photocatalytic transformations using fluorinated feedstocks, the assessment of their reactivity and selectivity, and the isolation of target molecules. The Italian partner will conduct advanced mechanistic and photophysical investigations of the regenerative photocatalyst using state-of-the-art tools. This synergy between synthetic chemistry and photophysical characterization ensures a comprehensive understanding of both reactivity and mechanism. Ultrafast Transient Absorption Spectroscopy (TAS) will monitor in real time the photoinduced fragmentation and recombination events underlying the regenerative cycle. UV-Vis and steady-state spectroscopies will characterize key intermediates and assess catalyst stability. Electron Paramagnetic Resonance (EPR) spectroscopy will detect and identify radical intermediates such as SF·and CFH·formed during defluorinative steps. Density Functional Theory (DFT) calculations will model electron-transfer pathways, activation energies, and structure-reactivity relationships. This combined synthetic, spectroscopic, and computational approach exemplifies interdisciplinarity, integrating molecular design, photophysical analysis, and theoretical modeling to achieve mechanistic understanding and catalyst optimization.