PhD Defense of Athulya Nadol

Prof. BONHOMME Christian

Rapporteur

 Prof. LCMCP, UMR 7574, Sorbonne Université, CNRS, 75005 Paris, France

Dr. FLORIAN

Pierre

Rapporteur

IR. CNRS, CEMHTI UPR3079, Orléans, F-45071 Orléans, France

Dr. LAURENCIN  Danielle

Member

DR. ICGM - UMR5253, Pôle Chimie, Balard Recherche 1919, route de Mende 34293 MONTPELLIER cedex 5, France

Dr. LE POLLES  Laurent

Member

MCF-HDR. ENSCR, UMR 6226 (UL-CNRS) Ecole Nationale Supérieure de Chimie de Rennes

Dr. POURPOINT  Frédérique

Thesis supervisor

MCF-HDR. Centrale Lille, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, F-59000 Lille, France

Prof. VOLKRINGER Christophe

Thesis Co-supervisor

PR. Centrale Lille, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, F-59000 Lille, France

ssNMR, MOF, CO₂, H₂, steam, adsorption

Metal organic frameworks (MOFs) have garnered significant interest in recent years due to their remarkable structural diversity and wide range of potential applications, including catalysis and gas storage. Multinuclear solid-state nuclear magnetic resonance (ssNMR) facilitates a comprehensive examination of the various elements constituting the MOF structure, yielding insights into their local environment and interactions. Furthermore, the porous nature of MOFs enables the adsorption of gas molecules, whose orientation, adsorption sites, and dynamics within the MOF matrix can be effectively characterized using ssNMR.

In this thesis, we examined the CO₂ adsorption properties of the UiO-66 MOF series through ¹³C ssNMR techniques. The research distinguishes between physisorbed and chemisorbed CO₂, pinpointing specific adsorption sites and providing significant insights into the interactions between CO₂ and the MOF framework.

Furthermore, the thesis explored the crucial stability under humid conditions of the hybrid materials, which is essential for practical gas storage applications. The steam stability of three UiO-66 family MOFs is investigated, using high-field ⁹¹Zr ssNMR for the first time to assess structural changes in the Zr clusters under steam flow at temperatures between 80 and 200°C. UiO-66 and UiO-66-Fum remain stable, while UiO-67-NH₂ degrades at lower temperatures but is stable at 200°C due to reduced water condensation. The study further demonstrates the use of ⁹¹Zr and ^47/49Ti highfield ssNMR to examine the bimetallic UiO-66(Zr/Ti), helping to understanding of the influence of Ti insertion in the Zr environment.

We also investigated the insertion of D₂ into MIL-96 (Al). Two distinct peaks in the ²H magic angle spinning NMR experiment were observed. We were able to identify an exchange between these sites. After few months, the ²H ssNMR spectrum is drastically different, proving a change in the interaction between the D₂ and the MOF. These findings highlight the potential of MOFs with micro-sized pores as promising H₂/D₂ storage materials.

The ability of ssNMR to provide detailed information on both the framework and the guest molecules makes it an invaluable tool for enhancing the understanding of MOFs and their prospective applications, thereby contributing to the development of high-performance materials for energy applications.