Controlled defects in metal-organic frameworks for enhanced adsorption and catalytic properties

Abstract

Metal organic frameworks (MOFs) are a new class of crystalline, hybrid and porous materials formed by linking metal clusters and organic ligands via strong bonds. Due to their high porosity, large surface areas, and high versatility, MOFs are widely used in gas storage, adsorption, catalysis, drug delivery and sensing. Because of its strong chemical bonding and high coordination number, the Zr-based cluster, Zr6O4(OH)4(CO2)12, found in UiO-66 (Zr6O4(OH)4(BDC)6; (BDC benzene dicarboxylate) is one of the most stable inorganic clusters and therefore is extensively employed as a platform for the construction of thermally and chemically stable MOFs. Recently, it has been shown that modulated synthesis routes by using monocarboxylate linkers such as formic acid, acetic acid and trifluoro-acetic acid promote the formation of defects within the MOF structure. These defects affect the textural features, the stability and the activity of UiO-66. In this work, we aim to control the defects in UiO-66 structure and to study their effects on Arsenic adsorption. To this end, different defected UiO-66 are synthesized using two distinct modulators acetic acid and trifluoro-acetic acid. The amount of these modulators is varied and the obtained MOFs are characterized using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Brunauer, Emmett and Teller (BET) and thermogravimetric analysis (TGA). The obtained MOF structures are used as adsorbents for arsenic removal from water. In addition, porosity and high surface area make the MOFs interesting candidates as heterogenous catalysts with active nanoparticles in the framework. The pores in the framework can define the size of the nanoparticles and also function as molecular sieves and thereby introduce catalytic selectivity on the reactant, intermediate and products if the catalytic process is carried out in the pores. The goal of the second subject is to prepare new catalysts with palladium nanoparticles deposited on a series of functionalized UiO-66 struct