Carbon dioxide levels have been steadily increasing over the past decades; as of 2019 (411 ppm), CO2 levels are at their highest in over 40 years (330 ppm in 1977); consequently, regulations in certain areas require the reduction of CO2 emissions to combat this trend. For effective carbon capture, we require a sorbent that has high adsorption capacity, stability, and recyclability; in addition, an efficient and economical way to release the captured gas is needed as well. Metal-organic frameworks (MOFs) possess a high surface area for adsorption, but releasing the stored gases requires additional energy input that limits the overall efficiency of carbon capture. Ag/UiO-66 provides a thermally stable complex with a high surface for adsorption of CO2 while the silver nanoparticles utilize light-induced local heating to act as a photoswitch for dynamic release of CO2; visible light in the 400 nm spectrum is used to liberate the captured CO2.

Yes / Mitoxantrone (MTX) is a drug employed in breast cancer treatment, but its application is largely limited due to side effects. A controlled delivery approach can potentially reduce the side effects. In this study, two zirconium (Zr)-based MOFs, UiO-66 and UiO-66-NH2, were studied for a more controlled delivery of MTX with a 40% and 21% loading capacity, respectively. Characterisation via powder X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectrometry, scanning electron microscopy, and dynamic light scattering confirmed the integrity of structure post-MTX loading. UV–vis spectrophotometry revealed distinctive release profiles, with UiO-66-MTX exhibiting a 25% cumulative release after 96 h in water and 120 h in PBS +10% FBS. UiO-66-NH2-MTX displayed a more sustained release, reaching 62% in water and 47% in PBS +10% FBS after 168 h. The interaction between MTX and the MOFs was also proposed based on computational modelling, suggesting a stronger interaction of UiO-66NH2 and MTX, and an optimised interaction of MTX in the tetrahedral and octahedral pores of the MOFs. The study also reports the release profile of the drug and antiproliferative activity against a panel of breast cancer cell lines (MDA-MB-231, MDA-MB-468, and MCF7) and a normal breast epithelial cell line (MCF10A). MTX-encapsulated MOFs were thoroughly characterised, and their biological activity was assessed in vitro. MTT cell viability assay indicated a higher IC50 value for MTX-loaded MOFs compared to free MTX in physiological conditions, albeit with a slower release profile. These findings suggest the potential of these MTX-loaded MOFs as an alternative avenue for formulation to mitigate side effects. / A.R. would like to thank The Royal Society (RGS\R1\221399) and the MRC Confidence in Concept grant (RM0039); MAA is grateful for HPC resources via membership of the UK’s HEC Materials Chemistry Consortium, which is funded by EPSRC (EP/X035859), this work used the UK Materials and Molecular Modelling Hub, which is partially funded by EPSRC (EP/T022213).

Metal-organic frameworks (MOFs) are a class of highly crystalline nanoporous materials that self-assemble from inorganic metal oxide clusters and multitopic organic linkers. MOFs can be altered in terms of the types of metals and structures of organic linkers used, allowing for a high degree of customization and manipulation of the synergistic chemical or physical properties that arise from the precise coordination of their molecular components, including exceptionally large surface area and pore size. Zirconium-based MOFs, called UiOs in honor of their conception at the University of Oslo, also show remarkable chemical stability in both acidic and basic environments, making them excellent candidates for biomedical applications as drug delivery systems, where they can either function as molecular cargo ships, with drugs packed into their pores, or as controlled release systems, in which drug molecules are directly attached to their ligands for precise delivery. The objective of this work is to prepare water-stable MOFs whose linkers are decorated with functional groups that have potential compatibility in drug delivery systems and to explore the efficacy of certain synthesis conditions in terms of the crystallinity of the MOF product. Thus, we hope to establish a basis for the ligation of anticancer drugs and fluorescent tags to MOFs for their controlled release at a specified location within the body. These targeted release mechanisms represent new therapeutic possibilities in terms of cancer treatment as their specificity would mitigate damage to healthy tissues, thereby addressing one of the greatest weakness of present treatment options.

Metal–organic frameworks (MOFs) represent an important platform to immobilize and stabilize electroactive molecular catalysts due to their porosity, high surface area and well characterized three-dimensional structure. Most efforts in this area have been dedicated to the development of photocatalysts and traditional heterogeneous catalysts based on both precious and abundant transition metals. However, little work has been done to design nickel-based MOF electrocatalysts for organic synthesis. In this work we describe the synthesis of three linkers containing a bipyridine moiety, where two of the linkers are dicarboxylate extended linkers and one is a bispyrazole extended linker. The two dicarboxylate linkers are combined with zirconium clusters to build MOFs of the UiO-n family. The bispyrazole linker was used to synthesize copper-based MOFs. The developed MOFs function as support for the immobilization of nickel (II) species in isolated sites within the frameworks. Following this, the redox properties of these MOFs were studied by the means of electrochemistry. The structure of the organic linkers was confirmed by 1H NMR spectroscopy and mass spectrometry, and two of the linkers are new molecules never synthesized before. The synthesized MOFs were characterized by powder X-ray diffraction, where the MOFs of the UiO-n family showed small crystallite sizes. Similarly, the MOFs based on the bispyrazole linker showed low crystallinity. Metalation of the MOFs with a [Ni(phen)3]Cl2 complex was studied using UV-Vis spectroscopy and scanning electron microscopy, both techniques confirmed the immobilization of the nickel catalyst in the UiO-n MOFs. The electrochemical properties of the MOFs were studied using cyclic voltammetry. Both UiO-n MOFs showed a non-reversible event for the reduction of Ni(II) and the MOFs based on the bispyrazole linker showed a quasi-reversible event for the Cu(II)/Cu(I) couple.

[ES] La presente Tesis Doctoral ha investigado el desarrollo de fotocatalizadores heterogéneos tipo MOF con topología UiO-66 y MIL-125 para la obtención de combustibles solares a partir del agua y del CO2. Inicialmente, en la introducción se ha revisado el estado del arte actual sobre el empleo de combustibles fósiles, las energías renovables y los combustibles solares como vectores energéticos. En esta sección se ha enfatizado sobre los procesos de fotocatálisis basados en semiconductores inorgánicos y MOFs para obtener combustibles solares. Los resultados de la tesis indican que el material tipo MOF UiO-66(Zr)-NH2 es un fotocatalizador más eficiente que sus análogos UiO- 66(Zr)-X (X: H o NO2) o que el MOF de referencia de titanio MIL-125(Ti)-NH2 para la obtención de hidrógeno a partir de la mezcla de agua y glicerol. Por otro lado, se ha demostrado la posibilidad de desarrollar materiales UiO- 66(Zr)-X (X: NH2 o NO2) con defectos estructurales introducidos con ácido acético o trifluoroacético como moduladores y que presentan actividades fotocatalíticias y eficiencias de separación de carga fotoinducida mejoradas para la generación de hidrógeno a partir de mezclas de agua y/o metanol. En esta Tesis también se ha demostrado la importancia del ligando 2- nitrotereftalato en la preparación de fotocatalizadores activos mono- o bimetálicos de Zr(IV) y Zr(IV)/Ti(IV) con topología UiO-66 respecto a los análogos preparados con el ligando 2-aminoteftalato. El material RuOx@UiO- 66(Zr/Ti)-NO2 mostró la máxima actividad fotocatalítica para la reacción de hidrogenación en fase gas de CO2 a CH4 y se propuso que opera bajo un mecanismo dual fotoquímico y fototérmico. / [CA] La present Tesi Doctoral ha investigat el desenvolupament de fotocatalitzadors heterogenis tipus MOF amb topologia UiO-66 i MIL-125 per a l'obtenció de combustibles solars a partir de l'aigua i del CO¿. Inicialment, en la introducció s'ha revisat l'estat de l'art actual sobre l'ús de combustibles fòssils, les energies renovables i els combustibles solars com a vectors energètics. En esta secció s'ha emfatitzat sobre els processos de fotocatàlisis basats en semiconductors inorgànics i MOFs per a obtindre combustibles solars. Els resultats de la Tesi indiquen que el material UiO- 66(Zr)- NH2 és un fotocatalizador més eficient que els anàlegs UiO- 66(Zr)- X (X: H o NO2) o que el referent de MOF de titani MIL-125(Ti)-NH2 per a l'obtenció d'hidrogen a partir de mescles d'aigua i glicerol. D'altra banda, s'ha demostrat la possibilitat de desenvolupar materials UiO-66(Zr)-X (X: NH2 o NO2) amb defectes estructurals introduïts amb àcid acètic o trifluoroacétic com a moduladors i que presenten activitats fotocatalítics i eficiències de separació de càrrega fotoinducida millorades per a la generació d'hidrogen a partir de mescles d'aigua i/o metanol. En esta tesi també s'ha demostrat la importància del lligant 2- nitrotereftalat en la preparació de fotocatalitzadors actius mono- o bimetàl·lics de Zr(IV) i Zr(IV)/Ti(IV) amb topologia UiO-66 respecte als anàlegs preparats amb el lligant 2-aminoteftalat. El material RuOx@UiO- 66(Zr/Ti)-NO2 va mostrar la màxima activitat fotocatalítica per a la reacció d'hidrogenació en fase gas de CO¿ a CH4 i es va proposar que opera per un mecanisme dual fotoquímic i fototérmic. / [EN] This PhD Thesis has investigated the development of heterogeneous MOF- type photocatalysts with UiO-66 and MIL-125 topology to obtain solar fuels from water and CO2. Initially, the introduction has reviewed the current state of the art on the use of fossil fuels, renewable energies and solar fuels as energy carriers. In this section, emphasis has been placed on photocatalysis processes based on inorganic semiconductors and MOFs to obtain solar fuels. The results of the thesis indicate that the MOF-type material UiO-66(Zr)-NH2 is a more efficient photocatalyst than the analogues UiO-66(Zr)-X (X: H or NO2) or the titanium MOF MIL-125(Ti)-NH2 for obtaining H2 from the mixtures of water and glycerol. On the other hand, the possibility of developing UiO-66(Zr)-X (X: NH2 or NO2) materials with structural defects introduced with AA or TFA as modulators and presenting enhanced photocatalytic activities and photoinduced charge separation efficiencies for the generation of H2 from water and/or CH3OH mixtures has been demonstrated. This Thesis has also demonstrated the importance of the 2-nitroterephthalate ligand in the preparation of mono- or bimetallic Zr(IV) and Zr(IV)/Ti(IV) active photocatalysts with UiO-66 topology with respect to the analogues prepared with the 2-aminoterephthalate ligand. The RuOx@UiO-66(Zr/Ti)-NO2 material showed the highest activity compared to RuOx@UiO-66(Zr/Ti)-NO2 material. / Rueda Navarro, CM. (2024). Metal-Organic Framework-Based Photocatalysts for Fuels Production [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/213302