Synthesis, Structure, White-light Emission, Sensing and Catalytic Studies on Metal-organic Framework (Mof) Compounds

Abstract

Metal Organic Framework (MOF) compounds are now recognized as a distinctive area of research in the fields of chemistry, materials, and other related sciences. The MOF compounds offer many potential applications towards gas sorption, catalysis, ionic conductivity, sensing, etc. These compounds are formed between inorganic metal ions connected by organic linkers. The framework offers scope to investigate magnetism, luminescence, ferroelectricity, etc., the open pores / channels present in the compounds can be useful for adsorption, separation, and catalysis. In this thesis, the various aspects of metal-organic frameworks (MOFs) compounds are presented. As part of this study, synthesis of three ligands, 4,4′-sulfonylbis(phenylene)bis(oxamate), 2, 5-bis(prop-2-yn-1-yloxy)terephthalic acid and 5-(carboxyformamido)isophthalic acid has been accomplished. These ligands, helped in the preparation of MOFs of transition metals (Mn, Co, Ni, Cu Cd), rare-earth metals (Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy) and mixed metals (4d-4f). Structure of the synthesized compounds has been determined by single crystal X-ray diffraction technique. Magnetic properties of the lanthanide and transition metal-based compounds have been studied by SQUID magnetometer and the magnetic behaviours have been correlated with their structures using suitable theoretical model. Metal nanoparticles embedded in the MOF template have been prepared using Co and Ni MOFs as sacrificial template. Detailed catalytic studies using the prepared MOFs as well as MOFs incorporated with metal nanoparticles were carried out. In selected cases, the labile nature of the lattice water molecules was explored by carrying out in-situ single crystal to single crystal (SCSC) structural transformation studies. In addition, time dependent transformation from lower dimensional (2D) to higher dimensional (3D) MOF structures were examined. Ligand-sensitized metal centre emission has been studied on the lanthanide MOFs. The prepared compounds were employed in the study of sensing of highly oxidizing anions, hazardous toxic cations, pesticide compounds, nitroaromatic compounds. Tb3+ and Eu3+ ions doped in blue light emitting Y- MOF compound and white light emitting materials have been achieved. The thesis contains seven chapters. A brief overview of the subject matter of each of the chapters is given below. Chapter 1 of the thesis presents a brief overview on metal-organic framework, MOF derived compounds and summarizes its various important properties. In Chapter 2, the synthesis, structure, luminescence sensing of the toxic anions like Cr2O72- and CrO42- and heterogeneous catalytic nature of a Cd – MOF using 4,4′-sulfonyl bis(phenylene)bis(oxamate) ligand are presented. In Chapter 3, the synthesis of a new ligand, 5-(carboxyformamido)isophthalic acid and its use for the synthesis of Mn and Cd – based MOF compounds are presented. Here, the synthesis, structure,xi magnetic property, luminescence sensing of Hg2+ ion, and the use of the bifunctionality of the MOFs towards the heterogeneous catalysis has demonstrated. In Chapter 4, the synthesis, structure, magnetic properties of Co and Ni MOF compounds employing new 2, 5-bis(prop-2-yn-1-yloxy)terephthalic acid ligand and use of the compounds as sacrificial templates to prepare metal nanoparticles dispersed in carbon matrix and Pd nanoparticles incorporation and their catalytic nature towards heterogeneous organic catalysis has presented. In Chapter 5, a new series of Cu – MOF has synthesized and explored the utility of the MOFs in different fields. The synthesis, structure, magnetic properties, single crystal to single crystal transformation and bifunctional acid base organic catalytic activity has been explored of these copper - MOFs. In Chapter 6, synthesis, structure, magnetic, catalytic, sensing of the toxic cations, white light emission of a series of rare-earth metal containing MOF compounds are presented. In Chapter 7, introduction of some π conjugated chelating ligands in the synthesis of rare earth MOFs for luminescence enhancement has been accomplished. The detailed study of structure, magnetic, catalytic, sensing of the nitroaromatics, pesticides, white light emission of rare-earth metal MOFs are presented.