Synthesis and Investigation of Zirconium Metal-Organic Frameworks For Adsorption Application

Abstract

The thesis titled “Synthesis and Investigation of Zirconium Metal-Organic Frameworks for adsorption Application” comprehend the work on synthesis of functionalised zirconium based UiO-66 type metal-organic framework for the adsorptive removal of contaminants from water. A green method for the synthesis of stable, free carboxylic functionalised MOF is developed. The promising outcomes of the strategies employed are confirmed by the characterization of the MOF. The MOF is utilised in the simultaneous adsorption of methylene blue dye and heavy metal ions (Lead and Cadmium) from aqueous solution. Under optimised condition the removal capacity of the MOF for cadmium, lead and methylene blue are found to be 37 mg g-1, 100 mg g-1 and 169 mg g-1 respectively. The maximum adsorption of MB dye among the other adsorbates is due to strong ionic interaction between MOF adsorbent and cationic MB dye. Lead adsorbs fairly better than cadmium because of its smaller size and the interaction with free carboxylic group present in the MOF. A fluorescence active zirconium based MOF synthesised from mixed ligand strategy displayed sensitive detection ability for p-nitrophenol along with rapid adsorption. In-house synthesised fluorescence active trifunctional ligand namely H3ntb (4,4ʼ,4ʼʼ- Nitrilotrisbenzoic acid) and BDC (1,4-Benzenedicarboxylic acid) are used in various proportions to synthesize MOF. PXRD studies affirmed the formation of crystalline phase and TGA revealed the effect of structural defects on framework integrity. The trifunctional ligand imparted the defects in the framework due to its inability in forming continuous array for crystalline network. As a result, increase in the proportion of trifunctional ligand during synthesis induced more defects in the framework and lesser stability to the MOF. The fluorescence active MOF is able to detect p-nitrophenol at low concentration and obeys Langmuir isotherm for adsorption with maximum adsorption capacity of 62 mg g-1. The work presented in this thesis illustrate the efficacious synthesis and application of zirconium metal-organic frameworks for adsorptive removal of contaminants from water.