Cluster Control of Reactivity and Grafting in Heterometallic Frameworks

• Autores: ANA MARIA RUBIO GASPAR
• Directores de la Tesis: Carlos Martí Gastaldo (dir. tes.), Francisco García Cirujano (codir. tes.)
• Lectura: En la Universitat de València ( España ) en 2024
• Idioma: inglés
• Número de páginas: 216
• Tribunal Calificador de la Tesis: Tatjana N. Parac-Vogt (presid.), Felipe Gándara Barragán (secret.), Jorge Andrés Rodríguez Navarro (voc.)
• Programa de doctorado: Programa de Doctorado en Química por la Universitat de València (Estudi General) y la Universitat Politècnica de València
• Materias:
  • Química
• Enlaces
  • Tesis en acceso abierto en: TESEO
• Resumen

  • This thesis is based on the introduction of functionalities to Metal-Organic Frameworks from the node, or cluster. Particularly, it discusses the role of Heterometallic MOFs in fields such as chemical reactivity and the grafting of amines. These new functionalities in heterometallic MOFs arise from the exact control of the metals distribution in the material. In our case, the exact control is based on the composition of the cluster itself, composed of more than one metal, rather than an order of the clusters.

    Chapter 1 provides an overview of the different approaches followed in the literature to incorporate functionalities to reticular materials from its cluster, citing the different strategies found. These include Direct Synthesis, Post-Synthetic Metal Exchange and the Grafting of species, to cite a few. For each of these strategies, both examples and advantages, drawbacks and applications have been discussed, with the aim of providing the reader with a general understanding of the area.

    In Chapter 2, we focus on the heterometallic MUV-101(M) family with M= Ni, Co and Fe, composed of trinuclear TiM2 clusters, which is isoreticular to homometallic MIL-100. As we found, apart from the Lewis acid character common to the rest of the family, MUV-101(Fe) possesses Brønsted acidity, being this dictated directly from the cluster composition. The combination of both types of acidities in the framework, makes of MUV-101(Fe) an efficient heterogeneous catalyst for the aminolysis reaction of epoxides. The recyclability and scope of the catalyst were examined, demonstrating its efficacy for a broad range of amines and epoxides. Additionally, this material could be employed for the gram-scale synthesis of the natural drug propranolol.

    Chapter 3 presents the selective grafting of a diamine, DAP, to heterometallic MUV-10 and MUV-12, being the latter an isoreticular expansion of MUV-10 with the same tetrameric cluster Ti2Ca2. The fact that the amine is attached only to the softer Ca2+ centres, leaves the Ti4+ centre uncoordinated, maintaining its Lewis acid character. Methylation of MUV-12-DAP with CH3I serves to incorporate a iodide anion to the framework. This anion, together with Lewis acidity, is key for substrate activation in the CO2 cycloaddition to epoxides. With our strategy, a bifunctional catalyst is achieved thus separating from the need of adding a co-catalyst to the reaction media. Overall, this exemplifies the potential for incorporating varied functionalities in heterometallic reticular materials, useful in catalysis.

    In Chapter 4, we continue exploring the grafting of amines to MUV-10. In this case, we chose a tetraamine, TETA, for carrying out this project. Single-Crystal X-Ray Diffraction studies allowed us to obtain the crystal structure of MUV-10-TETA. As it was found, the tetraamine is accommodated inside the octahedral cavities of the framework, instead of the cubooctahedral cavities. Even this kind of cavities are quite similar in size, the pore windows of the octahedral cavities are much smaller imposing the need for computational studied to understand its translocation mechanism. As it was determined, the translocation of TETA involved an unfolding of itself and a reconfiguration of the windows. This window reconfiguration involved the sequential breaking of two of the four coordination bonds of the softer Ca2+ cations, which contribute to a widening of the window. The Ti4+ cations bonding distances do not suffer any significant change, avoiding the structural collapse of the framework. Additionally, as we demonstrate, this grafting mode of TETA confers greater stability towards humid air than its diamine counterpart, MUV-10-DAP, a key aspect for the final applicability of these grafted porous materials.