Thèse Next-Ox Catalyse de Nouvelle Génération pour un Avenir Bas Carbone de la Synthèse MécanoChimique à l'Oxydation PhotoCatalytique H/F Doctorat.Gouv.Fr

Établissement : Université de Toulouse École doctorale : SDM - SCIENCES DE LA MATIERE - Toulouse Laboratoire de recherche : LCC - Laboratoire de Chimie de Coordination Direction de la thèse : Dominique AGUSTIN ORCID 0000000319338442 Début de la thèse : 2027-08-27 Date limite de candidature : 2026-11-23T23:59:59 Voir la version anglaise The chemical industry is facing a fundamental challenge: how can we continue producing the high-value chemicals that modern society depends on while using less energy, fewer raw materials and generating less waste? This challenge is not only environmental but also economic. Energy, solvents and raw materials represent major costs in chemical manufacturing, creating a strong incentive to develop catalytic processes that are simultaneously more sustainable and more efficient.
A promising strategy is to combine renewable feedstocks, advanced catalysts and alternative reaction technologies. Biomass-derived molecules are particularly attractive because they can provide renewable building blocks for high-value chemicals.
At the heart of this project are molybdenum- and vanadium-based polyoxometalates (POMs)-versatile molecular catalysts whose composition and electronic structure can be precisely tuned. Systems such as [PMoO40]3-, [PMoVO40]4-, [PMoVO40]5- and [V10O28]6- offer an opportunity to investigate how changes in metal composition control redox behaviour and catalytic performance. Immobilising these species on functionalized supports (silica, Merrifield resin, chitosan and -PGA) could further improve catalyst recovery, stability and practical applicability.
The real opportunity, however, is to rethink how these catalysts are made and how their reactions are activated. Conventional catalyst synthesis often relies on solvents, purification and energy-intensive drying. Mechanochemistry offers a fundamentally different approach, using mechanical energy to create functional catalytic materials with little or no bulk solvent. At the same time, replacing conventional thermal with light-driven photocatalysis could reduce the energy required to activate oxidation reactions.
This creates a unique research platform in which catalyst synthesis, catalyst structure, light absorption and catalytic performance can be studied as one connected system. The project will determine how mechanochemical conditions and Mo/V composition influence catalyst properties, and how these properties translate into thermal and photocatalytic oxidation activity. Spectroscopic tools such as UV-Vis and diffuse reflectance spectroscopy will be used to understand and predict photocatalytic behaviour rather than relying solely on trial-and-error experimentation.
Crucially, the project goes beyond simply developing a catalyst that works. Its success will be judged by whether the whole process makes scientific, environmental and economic sense. Catalyst productivity, selectivity, energy demand, solvent use, PMI, E-factor and carbon footprint will be evaluated to identify systems that offer genuine advantages over conventional approaches.
Answering this quests and challenges could provide new principles for designing next-generation oxidation processes and offer a pathway towards more resource-efficient, economically competitive and low-carbon chemical manufacturing.

The LCC group will contribute with the expertise in classical catalysis process - using organic solvent-free protocol with thermal activation , in the synthesis and characterization of the catalysts and their ionic grafting used to immobilize the catalyst for recovery purposes and in the biomass valorization. As a project partner, the University of Zagreb (UNIZG), Faculty of Science will contribute complementary expertise in mechanochemistry, coordination chemistry, advanced physicochemical characterisation and photocatalysis.
The proposed contribution is designed to introduce combination of methods, techniques and experimental capabilities that are not currently available within the French partner laboratory, thereby providing a distinct added value and strengthening the interdisciplinary character of the project.

The objectives have been summarized in 3 areas

Development of Catalysts

- To develop Mo- and V-based catalytic materials through conventional and solvent-free/solvent-minimised mechanochemical synthesis, including supported catalyst, and to optimise their preparation in terms of material efficiency, reproducibility and energy consumption.
- To establish structure-property relationships through comprehensive physicochemical characterisation, with particular emphasis on UV-Vis and diffuse reflectance spectroscopy for determining light absorption and optical band-gap energies.

Oxidation catalysis of molecules from biomass

- To develop energy-efficient thermal oxidation processes for the conversion of biomass-derived and bio-based molecules into value-added products,
- To develop energy-efficient photocatalytic oxidation processes for the conversion of biomass-derived and bio-based alcohols into value-added products,
- To investigate the influence of Mo/V composition, catalyst structure, ligand environment and support properties on catalytic activity, selectivity and photocatalytic performance, and to establish the relationship between optical properties and catalytic behaviour.
- To compare thermal and photocatalytic activation in terms of catalytic performance and energy demand, while investigating low-impact reaction conditions, including reduced solvent use and, where feasible, air or molecular oxygen as the terminal oxidant.

Comparison metrics

- To quantitatively evaluate the environmental performance of the developed processes using green chemistry metrics and carbon-footprint assessment, including PMI, E-factor, solvent intensity, energy consumption and greenhouse-gas emissions, in order to identify catalyst-process combinations with the greatest potential for low-carbon chemical manufacturing.
For each part of the project, the methods have been separated.

1. Synthesis of POM Catalysts and their grafting on supports

Sustainable catalyst preparation and mechanochemistry
The synthesis of the Mo- and V-based catalysts (coordination complexes and polyoxometalates) will be done in LCC using the classical solution chemistry in batch. This requires mainly metal oxides, aqueous solutions and strong acids in order to create the metal precursors or the POMS and organic solvent. This part, high kowledge of the French group, will be the basis of the study. The UNIZG will further develop Mo- and V-based catalysts obtained in France using solvent-free or solvent-minimised mechanochemical synthesis. Conventional synthesis of POMs frequently involves dissolution of metal precursors in relatively large volumes of solvent, followed by prolonged heating and subsequent solvent evaporation. Although such procedures can provide good structural control, they can generate significant environmental burdens through: consumption of solvents, solvent evaporation and associated emissions, energy required for heating and stirring, solvent purification and recovery, generation of liquid waste, and relatively low reaction concentration and material efficiency.
Mechanochemical synthesis offers a fundamentally different approach. Reactants will be combined in the solid state and activated through mechanical energy, allowing coordination and solid-state transformations to proceed with little or no bulk solvent. The project will therefore optimise parameters such as: reactant stoichiometry, milling time, milling frequency/intensity, ball-to-powder ratio, reaction concentration, use of catalytic quantities of liquid where strictly necessary, scale-up potential, and energy consumption per gram of catalyst produced.
This expertise represents an important complementary capability, as mechanochemical preparation of these functional coordination catalysts is not currently established among the French partners. The approach will be further evaluated using green metrics such as process mass intensity (PMI), E-factor, solvent intensity and energy consumption, allowing its environmental advantages to be quantitatively assessed.
The objective is not simply to demonstrate that the catalyst can be synthesised mechanochemically, but to determine whether the mechanochemical route provides a measurable environmental advantage over conventional solution synthesis.
Where both routes are experimentally feasible, they will be compared directly using green metrics.

To summarize:

At LCC
The Mo- and V-based polyoxometalate (POM) catalysts will be synthesised in France using improved protocols in solution. The work will consist into the synthesis of [PMoO40]3-, [PMoVO40]4-, [PMoVO40]5- and [V10O28]6- in their protonated forms or with organic cations. The organic cations will be chosen to be close the the pending functionalization of the supports.
Indeed, the catalysts can be supported in an ionic way on supports as silica, Merrifield resin, chitosan and -PGA. The grafting ensure catalyst recovery, and practical applicability.
at UNIZG
The Mo- and V-based polyoxometalate (POM) catalysts synthesised in France will be further developed at UNIZG using solvent-free or solvent-minimised mechanochemical synthesis, performed via planetary ball milling and/or shaker/mixer milling. Reaction parameters: stoichiometry, milling time, frequency/intensity, ball-to-powder ratio, reaction concentration, and (where unavoidable) minimal liquid-assisted grinding (LAG) additive will be systematically optimised.
Justification: Conventional solution-phase chemistry synthesis requires large solvent volumes, extended heating, and energy-intensive purification, generating substantial liquid waste and a poor E-factor. Mechanochemistry activates solid-state reactivity through mechanical energy input rather than thermal/solvent activation, eliminating or drastically reducing solvent use. This method has not previously been applied to these catalyst systems within the French partner laboratory, so its inclusion introduces a genuinely new synthetic capability to the consortium and directly targets the project's sustainability objectives at the synthesis stage.

2- Characterization of the catalysts

A strong emphasis will be placed on physical and physicochemical characterisation of the catalysts. Structural, spectroscopic, thermal, magnetic and optical techniques will be combined to establish detailed structure-property relationships.
In particular, UV-Vis spectroscopy and diffuse reflectance spectroscopy (DRS) will be used to investigate light absorption and determine the optical band-gap energies of the solid catalysts. These measurements will be performed before the photocatalytic studies and will be used to rationally select suitable irradiation wavelengths and reaction conditions.
This interdisciplinary characterisation will make it possible to connect the molecular and electronic structure of the catalysts with their optical and catalytic behaviour.

To summarize

2a - Structural and Compositional Characterisation
- Powder X-ray diffraction (PXRD): phase identity and crystallinity of mechanochemically obtained products versus solution-synthesised references
- FT-IR spectroscopy: confirmation of the synthesis of POMs
- Elemental (CHN) analysis: stoichiometric and purity verification
Justification: Establishing that the mechanochemical route yields materials structurally equivalent (or usefully distinct) from the conventionally synthesised catalysts is a prerequisite before any catalytic or environmental comparison is meaningful. PXRD provides the structural ground-truth; FT-IR and elemental analysis offer rapid, low-cost routine verification at each synthetic iteration.

2b- Spectroscopic and Electronic Characterisation
- UV-Vis spectroscopy (solution) and UV-Vis Diffuse Reflectance Spectroscopy, DRS (solid-state)
- IR spectroscopy
- NMR spectroscopy
Justification: UV-Vis/DRS is essential to the project's central photocatalytic hypothesis: band-gap energies derived from these measurements directly determine which irradiation wavelengths are selected for the photocatalytic experiments, ensuring mechanistically justified rather than arbitrary reaction conditions. FT-IR spectroscopy for vibrational assignment and can additionally monitor solid-state transformations during milling. NMR verifies solution-state structural integrity of soluble species as well as the nature of the grating on supports using solid state NMR in LCC.

2c- Thermal and Magnetic Characterisation
- Thermogravimetric analysis (TGA)
- Differential scanning calorimetry (DSC)
- Evans balance/ Electron paramagnetic resonance (EPR)
Justification: TGA/DSC establish thermal stability windows and detect solvate or hydrate content, both relevant to comparing mechanochemical versus solution products and to defining safe operating temperatures for the thermal-oxidation control experiments. Evans balance and EPR probe the magnetic/electronic environment of paramagnetic centre, providing mechanistic insight into metal-centred redox behaviour that underlies catalytic activity.

3- Catalytic Oxidation

The key sustainability hypothesis is that photocatalysis can reduce the energy intensity of oxidation processes by replacing or reducing conventional thermal activation.
Instead of relying exclusively on elevated temperature to overcome the activation barrier, photoexcitation of the catalyst will generate reactive electronic states capable of initiating the oxidation reaction under substantially milder conditions.
The project will therefore compare: conventional thermal oxidation with light-driven catalytic oxidation in terms of: reaction temperature, reaction time, energy consumption, substrate conversion, product selectivity, catalyst loading, oxidant consumption, solvent requirement, waste generation, and carbon footprint.

3a - Thermal catalysis (LCC)
- Parallel thermal-only oxidation runs under matched conditions
3b- Photocatalysis (UNIZG)
- Controlled-wavelength photoreactor (LED or Xe-lamp, wavelength selected from UV-Vis/DRS band-gap data)

- GC for conversion and product-selectivity quantification

Justification: Directly comparing light-driven and purely thermal oxidation, under otherwise identical conditions, is the only way to isolate a genuine photocatalytic contribution from conventional thermal activation. GC provides quantitative conversion/selectivity data across the alcohol substrate series, enabling systematic structure-reactivity analysis.

4- Studied substrates from biomass
The main catalytic objective will be the development of oxidation reactions, with particular emphasis on several molecules from (or derived from) biomass.
Vanillyl alcohol oxidation into vanillin will serve as an important model reaction, complemented by structurally related substrates such as benzyl alcohol, 4-methoxybenzyl alcohol, 4-hydroxybenzyl alcohol, 3,4-dimethoxybenzyl alcohol and piperonyl alcohol.
This substrate series will enable systematic investigation of the influence of electronic and structural effects on conversion and selectivity.
Furfural oxidation will be more complex reaction since it can lead to several compounds, but previous publlished works showed that different activations and different catalysts can lead to selectivities.
The work on this substrate will enable systematic investigation of the influence of catalyst, oxidant and activation mode to the nature and distribution of the isoled oxidation products.

For both substrates, air or molecular oxygen will be investigated as a sustainable oxidant.
The photocatalytic experiments will be guided by the optical properties determined by UV-Vis and DRS. Dark and thermal control experiments will be performed to distinguish genuine photocatalytic effects from conventional thermal oxidation.
Particular attention will be given to photoinduced charge-transfer processes and to understanding how the Mo or V centre and ligand architecture influence light absorption, charge separation and oxidation activity. Where technically appropriate, air will be investigated as the terminal oxidant. This would provide an additional sustainability advantage by avoiding stoichiometric quantities of potentially hazardous oxidants and reducing the formation of oxidant-derived waste.

5- Sustainability and Green-Metrics Assessment (both places)

Sustainability will be evaluated quantitatively at both stages of the process: catalyst synthesis and catalytic operation. The assessment will include PMI, E-factor, solvent consumption, energy demand, catalyst loading, conversion and selectivity, together with an evaluation of the carbon footprint and associated greenhouse-gas emissions.
The objective is to identify not simply the catalyst with the highest activity, but the catalyst-process combination that provides the best balance between catalytic efficiency, energy consumption, material efficiency and carbon emissions.
The combination of mechanochemistry and photocatalysis provides a complementary strategy: mechanochemistry addresses the solvent and waste footprint of catalyst preparation, while photocatalysis offers the possibility of reducing the energy demand of oxidation reactions by replacing conventional thermal activation with light.

- Process Mass Intensity (PMI) and E-factor calculations
- Solvent-intensity and energy-consumption quantification (mill and photoreactor energy logging)
- Carbon footprint / greenhouse-gas emissions estimation
Justification: Green metrics are calculated (not instrumental) outputs derived from mass-balance and energy data collected across the synthesis and catalysis stages. Their inclusion ensures the project's central question, whether mechanochemistry and photocatalysis offer measurable environmental advantages, not merely qualitative ones, is answered quantitatively and defensibly, allowing direct, numeric comparison between conventional and alternative routes at both the synthesis and catalytic-operation stages.