UC San Diego

Metal-organic frameworks (MOFs) are a hybrid class of porous materials that are comprised of metal clusters and bridging organic ligands. The modular nature these materials makes them suited for chemical strategies aimed at fine-tuning their structure and function. Significant efforts have been spent on developing MOFs for novel applications through the use of functionalized ligands. However, incorporation of functional groups on the ligands can introduce steric, solubility, and metal-coordinating characteristics that can interfere with MOF formation. By targeting the organic linking component of the a prefabricated MOF one can utilize various organic reactions to transform it into a new MOF with altered functional groups and thus different physical and chemical properties. The work in this thesis explores the development of functionalized MOFs through both prefunctionalization and postsynthetic modification (PSM) approaches on a variety of MOFs. In Chapter 2, the use of chiral tris(dipyrrinato) metalloligands was examined in an attempt to introduce chiral functionality into a set MOFs with distinct topologies realized through the use of a racemic analogue. The results further exemplify the difficulties associated with the functionalized linker strategy and suggest that PSM offers a more viable functionalization route. In Chapter 3, the versatile nature of the PSM approach is demonstrated with the successful incorporation of chiral, amine protected, and free carboxylic acid groups into an amine functionalized framework through the use of anhydrides. In Chapter 4, the scope and limitation of a multi-step PSM approach termed tandem PSM is discussed. A set a diverse multifunctional amide and urea MOFs were realized through tandem PSM. While there have been many studies investigating MOFs as heterogeneous catalysts, most examples utilize unsaturated metal sites. In Chapter 5, the utilization of carboxylic acid functionalized MOFs as a solid state Brønsted acid catalyst for the methanolysis of small epoxides is demonstrated. The use of PSM and moreover MOFs for commercial applications is limited by the chemical instability of many frameworks. Chapter 6 presents the synthesis of chemically robust frameworks and utilization of these materials in harsh PSM reaction conditions for the conversion of bromide groups to cyano groups