Metal-Organic Polyhedra as Building Blocks for the Generation of Porous Materials

Abstract

Aquesta tesi doctoral investiga l'ús dels poliedres metal·lorgànics (MOPs) com a estructures prefabricades per dissenyar xarxes poroses complexes i jeràrquiques. Els MOPs obren noves oportunitats en la creació de materials porosos amb aplicacions potencials en àmbits com la catàlisi, l'emmagatzematge de gasos i la descontaminació ambiental. Els objectius principals són: i) utilitzar la química de coordinació per integrar MOPs en xarxes metal·lorgàniques multicomponent (MOFs), i ii) desenvolupar xarxes jeràrquiques a través de la química covalent. La tesi destaca com els MOPs permeten controlar amb precisió l’estructura dels MOFs, millorant-ne tant la complexitat com la funcionalitat, i com es poden utilitzar per crear xarxes multicomponent estables i materials porosos amb propietats tunejables. A més, s'introdueix una metodologia innovadora per a la síntesi d’aerogels, amb la capacitat de modificar-ne les propietats fisicoquímiques mitjançant funcionalitzacions post-sintètiques. Els avenços exposats ofereixen noves perspectives per al desenvolupament de materials porosos més sofisticats i versàtils amb aplicacions en diversos àmbits.

Esta tesis doctoral investiga el uso de los poliedros metalorgánicos (MOPs) como estructuras prefabricadas para diseñar redes porosas complejas y jerárquicas. Los MOPs abren nuevas oportunidades en la creación de materiales porosos con aplicaciones potenciales en ámbitos como la catálisis, el almacenamiento de gases y la descontaminación ambiental. Los principales objetivos son: i) utilizar la química de coordinación para integrar MOPs en redes metalorgánicas multicomponente (MOFs), y ii) desarrollar redes jerárquicas a través de la química covalente. La tesis destaca cómo los MOPs permiten controlar con precisión la estructura de los MOFs, mejorando tanto la complejidad como la funcionalidad, y cómo se pueden utilizar para crear redes multicomponente estables y materiales porosos con propiedades ajustables. Además, se introduce una metodología innovadora para la síntesis de aerogeles, con la capacidad de modificar sus propiedades fisicoquímicas mediante funcionalizaciones post-sintéticas. Los avances expuestos ofrecen nuevas perspectivas para el desarrollo de materiales porosos más sofisticados y versátiles con aplicaciones en diversos ámbitos.

This PhD dissertation focuses on the advanced application of metal-organic polyhedra (MOPs) as pre-designed cavities and structure-directing agents to synthesize complex, hierarchically porous networks. By leveraging the distinctive properties of MOPs, this work demonstrates how they can open up new avenues in designing porous materials, enhancing both structural complexity and functional versatility. The research is guided by two main approaches: i) exploring coordination chemistry techniques to assemble MOPs into multicomponent metal-organic frameworks (MOFs), and ii) developing covalent chemistry strategies to construct hierarchically porous networks. Chapter 1 introduces the reader to the fascinating field of porous materials, tracing their evolution from the early discovery of natural zeolites to breakthroughs like silica aerogels, mesoporous silicas, and the more recent advancements in porous polymeric networks, MOFs, and covalent organic frameworks (COFs). While significant progress has been made in creating simpler bicomponent systems, designing intricate, hierarchical porous networks remains a major challenge. This chapter lays the groundwork for how MOPs can serve as versatile, prefabricated building blocks, offering unmatched precision in constructing complex porous architectures. By overcoming current limitations, MOPs open up new possibilities for synthesizing advanced porous materials, which hold promise for applications in catalysis, gas storage, and pollutant removal. Chapter 2 outlines the general and specific objectives of this thesis. Chapter 3 centers on developing a coordination-driven assembly strategy to integrate Rh(II)-based MOPs into multicomponent MOFs, achieving both atomic precision and enhanced structural complexity. By using MOPs as prefabricated cavities with strong structure-directing properties, the approach successfully replicated and further evolved the well-known HKUST-1 structure, leading to the creation of the three-component RhCu-btc-HKUST-1. This new structure demonstrates outstanding hydrolytic stability, attributed to the incorporation of robust Rh(II) paddlewheels that fortify the framework. The results underscore the versatility of MOPs, offering precise control over the organization of organic and metallic building blocks and enabling the design of intricately defined multicomponent frameworks. Chapter 4 broadens the use of MOPs as prefabricated cavities, pushing the synthesis of atomically precise four-component analogues of HKUST-1, thereby enhancing the complexity of the framework while preserving its accessibility and functionality. This chapter also takes an important step forward in controlling defects within MOF networks, where MOPs, with their strong structure-directing capabilities, allow control over defect placement within the lattice. This innovative approach unlocks new design possibilities, resulting in defective MOFs that exhibit remarkable flexibility and hierarchical porosity. These advancements mark a significant leap in the controlled design of defective MOFs, opening the door to novel material functionalities. Chapter 5 shifts the focus to the second major theme of this thesis: exploring the covalent cross-linking of Rh(II)-based MOPs to create extended porous networks. By harnessing dynamic covalent chemistry, MOPs are polymerized into hierarchically porous structures while crucially preserving the reactivity of the Rh(II) open metal sites for further post-synthetic modifications. These sites enable precise tuning of the aerogels' key properties, such as electrostatic charge and hydrophobicity, leading to significant improvements in their pollutant adsorption capabilities. This chapter demonstrates the effectiveness of this covalent chemistry strategy in developing robust and customizable materials with strong potential for applications in environmental remediation, catalysis, and sensing. Finally, Chapter 6 encapsulates the key discoveries and contributions of this work, emphasizing the transformative role of MOPs as versatile building blocks for creating complex, hierarchically porous, and multifunctional materials. These advancements pave the way for MOPs to become integral components in the design of next-generation porous materials, unlocking new possibilities for innovation across various fields.