Synthesis and characterization of giant porous molecules

Abstract

This PhD Thesis focuses on the assembly of metal-organic giant structures, specifically targeting mesoporous cages and oligomeric supramolecules, defined as structures with an internal cavity larger than 2 nm or an overall diameter exceeding 5 nm, respectively. The aim of this work is to explore strategies for obtaining permanently porous giant cage-based molecules. Special emphasis is placed on understanding the design principles and synthetic pathways required to construct such large, porous architectures, either through direct synthesis or post-synthetic modification. Ultimately, this study seeks to contribute to the development of robust, permanently porous giant molecules, expanding their potential for applications in areas such as molecular separation, catalysis, or storage. Chapter 1 provides an overview of the fundamentals of discrete metal-organic materials, including the self-assembly of metallacycles and the formation of three-dimensional metal-organic cages. This chapter reviews the synthetic approaches developed to date and introduces the key concepts underlying their design and synthesis. Particular emphasis is placed on the strategies used to construct giant assemblies and the progress achieved in this field so far. Chapter 2 specifies the general and specific objectives of this PhD Thesis. Chapter 3 presents the formation of the first family of oligomeric supramolecules synthesised via a stepwise approach. Specifically, it demonstrates how the connectivity of metal-organic polyhedra (MOPs) can be precisely controlled through a protection-deprotection strategy, enabling the formation of 1-connected cages. These cages serve as monomeric building blocks for the construction of oligomeric, cage-based supramolecules, including a dimer, a tetramer, and a satellite-like architecture. Finally, the permanent porosity of this new family of supramolecules is evaluated through CO₂ adsorption studies. Chapter 4 focuses on the synthesis of mesoporous MOPs capable of withstanding the desolvation process, enabling their application as solid-state adsorbents. To achieve this, an isoreticular expansion strategy was applied to a Rh(II)-based parent microporous MOP, leading to the formation of two novel mesoporous cages. This study highlights the critical influence of linker planarity on structural control. In particular, the use of a non-planar linker led to the formation of three unexpected architectures: a trigonal prism, a pentagonal macrocycle, and a hexagonal macrocycle. Finally, the permanent porosity of the isoreticularly expanded cages was confirmed through N₂, CO₂, and H₂O adsorption studies. Finally, Chapter 5 summarizes the key findings and main conclusions of this Thesis.

Date of Award	31 Oct 2025
Original language	English
Awarding Institution	Universitat Autònoma de Barcelona (UAB)
Supervisor	Arnau Carne Sanchez (Director) & Daniel Maspoch Comamala (Director)