Synthesis and characterisation of catalytically active metal-organic frameworks based on porphyrins

Abstract

Metal-organic frameworks (MOFs) are proving to be an exciting class of materials with unprecedented properties and high potential applications such as gas storage and separation, selective adsorption and separation of organic molecules, ion exchange and catalysis. The main aim of this work is to incorporate multifunctional organic ligands, which ideally contain two types of coordinating sites (primary and secondary), as building blocks for constructing catalytically active MOFs. The ligand chosen for this study was porphyrin with carboxylic group which has two types of coordinating sites; porphyrin core and carboxylic moiety. In this thesis, a three-step synthesis will be conducted to yield 4,4',4'',4'''-(porphyrin-5,10,15,20-tetrayl) tetrabenzoic acid, which will react with metal complexes such as Zn(II) or Cu(II) to form the MOF. The final target is to convert these MOFs into active catalyst by incorporating molybdenum via post-synthetic metalation. X-ray diffraction analysis of the crystals of the synthesized porphyrin ester revealed that the porphyrin core was coordinated to zinc atom. This result indicates that a metalloligand approach could also be used to get the MOF, by first incorporating the molybdenum to the porphyrin core (metalloligand) followed by the reaction of carboxylic groups with other metals to form the catalytically active MOF. Which either way is chosen, a solid ground work has been done for the continued research.