Ordered Porous Inorganic Fluorides as efficient Heterogeneous Catalysts – OPIFCat

To achieve a comprehensive understanding of the structure-property relationships of OPIF in heterogeneous catalysis, a collaborative research team has been built with complementary expertise on elaboration and characterization of polymers and fluorinated materials, heterogeneous catalysis, computational modelling and Solvay industry. The first Work Package (WP0) will be devoted to the project management. The preparation of OPIF materials (WP1 and WP3) requires trans-disciplinary skills (solid state and polymer chemistries) developed within two teams of IMMM (Le Mans). Their work will be guided by WP2 at IMN (Nantes) which will try to predict the best combination of surface chemical composition and atomic structure with absorbed molecular species to achieve high catalytic performances, which will be performed in WP4 at IC2MP (Poitiers). Finally, in the perspective of developing the use of OFIP materials prepared at industrial level, WP5 at Solvay will identify the synthesis conditions toward the scale-up.

- Optimized MgF2 NP preparation methodology to enable scaling up
- Immobilization of NP MgF2 on NP AlF3 in order to obtain supported catalysts.
- Immobilization of NP FeF3 on OPIF MgF2
- Templates capable of complexing M2+ metal cations to prepare supported OPIF catalysts
- DFT calculations identifying stable facets of MgF2 and AlF3, perfect and defective, and relating them to specific infrared absorption modes of CO.
- Prediction of a new Mg-AlFx monolayer surface phase, potentially catalytically active.
- Development of a new fluorination reaction by HF of HCSI in HFSI with HCl as the only recoverable by-product. Study on a larger scale by Solvay for its industrialization.

The OPIFCat project is a contribution to face the societal challenge to engineer a more sustainable world, as heterogeneous catalysis decreases the environmental fingerprint of industrial processes by using less natural resources and reduces the energy needs. By combining fundamental aspects and industrial developments, it proposes to significantly improve existing catalytic processes to prepare fluorinated molecules by applying an alternative one-step approach via a gas phase process and innovating catalyst architectures based on OPIF materials. Such catalytic reaction will afford to replace large volumes of non-recoverable effluents by only one by-product HCl, moreover recyclable, and to suppress also organic solvent and toxic reagents. Our objectives are to develop original catalysts containing friendly and abundant chemical elements for breakthrough catalytic performances compared to classical nanofluorides and ultimately, to reach eco-efficient catalytic industrial processes that will have a strong final impact both health and energy domains. It is also expected that these OPIF materials will have a positive impact on health by reducing the risk of inhalation compared to nanoparticles. From an economic point of view, such a technological advance would foreseen a real benefit, as the market is particularly competitive in the fields of batteries or agrochemistry and consequently, to increase the competitiveness in the industrial sector. Finally, properties of this new class of porous materials remain to be explored and OPIF materials could pave the future way to various applications.

Communications (conference)
1. «Synthèse de MgF2 de surface spécifique élevée pour la fluoration catalysée en phase gazeuse de la 2-chloropyridine« Y. Wang, J. Dieu, A. Guiet, J. Lhoste, A. Hémon-Ribaud, V. Maisonneuve, S. Brunet, 3ème Colloque Français de Chimie du Fluor (CFCF), Forges les eaux, mai 2022.
2. «Fluorures inorganiques poreux ordonnés comme catalyseurs hétérogènes efficients« A. Guiet, Y. Wang, A. Hémon-Ribaud, V. Maisonneuve, J. Lhoste, S. Brunet, 3ème Colloque Français de Chimie du Fluor (CFCF), Forges les eaux, mai 2022.
3. «Synthèse de copolymères à blocs amphiphiles à fonctionnalité terpyridine par PISA-RAFT en milieu aqueux« F. François, S. Piogé, S. Pascual, Colloque GFP grand Ouest, juillet 2022.

Article related to the ANR project:
1. «Controlled Morphology Synthesis of Nanostructured ß-AlF3-x(OH)x with Tunable Specific Surface Area« V. Camus-Génot, A. Guiet, J. Lhoste, F. Fayon, M. Body, S. Kodjikian, R. Moury, M. Leblanc, J.-L. Bobet, C. Legein, V. Maisonneuve, Crystal Growth Des. 21 (2021) 5914.

Articles in which the ANR is thanked but not directly related to the project:
2. «Missing one-dimensional red phosphorus chains encapsulated within single-walled carbon nanotubes« D.V. Rybkovskiy, V. O. Koroteev, A. Impellizzeri, A.A. Vorfolomeeva, E.Yu. Gerasimov, A. V. Okotrub, A. Chuvilin, L.G. Bulusheva, C.P. Ewels, ACS Nano 16(4) (2022) 6002.
3. «Asymmetrical Cross-Sectional Buckling in Arc-Prepared Multiwall Carbon Nanotubes Revealed by Iodine Filling« A. Cefas Torres-Dias, A. Impellizzeri, E. Picheau, L. Noé, A. Pénicaud, C.P. Ewels, M. Monthioux, MDPI C, 8(1) (2022) 10.
4. «Prismatic Edge Dislocations in graphite« J.G. McHugh, P. Mouratidis, A. Impellizzeri, K. Jolley, D. Erbahar, C.P. Ewels, Carbon 188 (2022) 401.

The fluorine element is used in domains as diverse as medicine, energy, microelectronics and everyday plastic objects. Rare in the natural state, a tremendous number of elegant syntheses of fluorinated organic compounds has been developed by using catalysts to improve both activity and selectivity. Catalyzed fluorination by HF in the gas phase is largely operated at industrial scale, essentially for non-functionalized aliphatic fluorinated compounds prepared from chlorinated precursors by Cl/F exchange. In contrast, this strategy is neither applicable to functionalized aliphatic fluorinated compounds due to the sensitivity of most organic functions towards HF, nor for fluoroaromatics which are essentially produced by 2 liquid phase reactions (Balz-Schiemann and HALEX). However, these reactions, poorly selective, generate large volumes of non-recoverable effluents. Therefore, new selective fluorination methods are needed, ideally more efficient, selective and environmentally sustainable. Such an alternative approach, already successfully used for non-functionalized aliphatic fluorinated molecules, is the one-step fluorination of chlorinated aromatic molecules via a gas phase process based Cl/F exchange under anhydrous HF involving catalysts. Additionally, no solvent is required and HCl is the only by-product which is recoverable. Recently, nanofluorides were used as efficient catalysts for the fluorination of 2-chloropyridine. While the selectivity of this reaction is optimal, the activity, related to the weak strength of Lewis acidity of active sites, could be enhanced by increasing the catalyst surface area. Indeed, under harsh conditions (HF gas at 350°C), the nanofluoride catalysts undergo a sintering process leading to a drastic loss of the initially promising surface areas. This stumbling block forces us to explore innovative directions in order to develop such materials, fulfilling the 3 key requirements of a catalyst: activity related to its specific area, selectivity and stability under extreme operating conditions.
The innovation of the OPIFCat project is to prepare inorganic fluorinated metallic materials as efficient, selective and stable catalysts under the harsh fluorination conditions of chlorinated reagents under HF gas. In this context, we will explore new architectures and innovative production methods focused on ordered porous inorganic fluorides (OPIFs) supposed to resist such conditions and whose design methodology will be soon patented by the team of IMMM. The chemical composition of the OPIF catalysts will be guided by computer modelling of reaction site chemistry. We will target new Cl/F exchange reactions involving nucleophilic aliphatic and aromatic substitution with five molecules which are involved in domains of energy, agrochemistry and medicine. This project aims to understand the catalyst structure-activity relationship and to establish a “catalyst library” with various strength of Lewis acidity which will help chemists to rapidly select the most appropriate catalyst for the Cl/F exchange as a function of the reactant characteristics (aliphatic/aromatic, activated or not, bearing one or several heteroatoms,…).
This OPIFCat project relies on a transdisciplinary consortium with complementary skills, and involves a large industrial group proactive in the sustainable energy transition. It is composed of highly qualified scientists with expertise in the elaboration of fluorinated and polymer materials (IMMM) as well as heterogeneous catalysis (IC2MP), and is completed by an expert of modelling interaction of nanomaterials with reactive species (IMN). Solvay will ensure the scale-up of the OPIF materials and their catalytic properties will be validated in a continuous tubular reactor.