New hybrid materials based on metal-organic frameworks for the removal of organic pollutants

Zusammenfassung

The growing awareness of the negative effects that industrial and human activities have on the environment and public health and, more specifically, on water resources, has led to the development of new strategies to mitigate the impact of these activities and guarantee environmental quality standards, having become one of the most important social challenges today. Among the different strategies proposed to guarantee efficient water management, the development of materials that allow the extraction and elimination of environmental contaminants stands out as a key. This Doctoral Thesis presents the development of new materials derived from metal-organic frameworks (MOFs) for the removal of organic contaminants such as dyes, phenols, and pharmaceutical products. As part of this process, different types of MOFs have been synthesized and used to the preparation of porous carbons and metal oxides. In order to facilitate their applicability, the prepared materials have been incorporated into supports such as membranes, magnetic stirrers and 3D printed devices. The obtained materials have been characterized with the adequate instrumental techniques and their applicability in the adsorption or photocatalytic degradation of different pollutants has been studied. In the first work, the preparation of a carbon composite membrane derived from a MIL-125-NH2 MOF has been carried out for the extraction of phenolic compounds. The derived carbon (C-MIL-125-NH2) has been prepared by carbonization of the precursor MOF at a high temperature under nitrogen atmosphere. It has shown fast adsorption kinetics of bisphenol A and 4-tert-butylphenol, reaching equilibrium in 25 minutes. Moreover, with a simple coating process, a carbon composite membrane (C-MIL-125- NH2-HM) has been obtained and tested in the dynamic extraction of the phenols under study, demonstrating good recyclability, excellent flow properties and a high efficiency for the preconcentration of both phenols. In the second work, the preparation of a titanium oxide, derived from NTU-9 type metal-organic framework, has been described. This titanium oxide (TiO2-NTU-9) was obtained by oxidation of the MOF precursor at 450 ¿C. TiO2-NTU-9 has exhibited 100% of methylene blue (MB) degradation in 2 hours thanks to its mixed anatase/rutile phase structure, as well as carbon doping. In addition, by a simple deposition method, a mechanically stable TiO2-NTU-9 coated stirrer (TiO2-NTU-9-S) has been prepared and tested for the elimination of MB, demonstrating excellent and easy recyclability. In the final work, to enhance the adsorption capacity of the MIL-100-Fe MOF, post-synthetic modification with sulfonic groups has been carried out by the grafting of aminomethanesulfonic acid (AMSA) onto the coordinatively unsaturated metal centers. The obtained, MIL-100-Fe-AMSA, has been used for the diclofenac (DCF) extraction, obtaining high extraction capacity (476 mg·g-1) thanks to the great affinity between DCF and the sulfonic groups. The functionalized MOF was immobilized in a 3D printing column, facilitating its use for the extraction, pre-concentration and analysis of low levels of DCF and ketoprofen in water samples.