Browsing by Author "Schott Verdugo, Eduardo"
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- ItemAdsorption properties of M-UiO-66 (M = Zr(iv); Hf(iv) or Ce(iv)) with BDC or PDC linker(Royal Society of Chemistry, 2024) González, Diego; Pazo Carballo, César Alexander; Camú Macaya, Esteban Alonso; Hidalgo-Rosa, Yoan; Zarate, Ximena; Escalona, Néstor; Schott Verdugo, EduardoThe increasing CO2 emissions and their direct impact on climate change due to the greenhouse effect are environmental issues that must be solved as soon as possible. Metal-organic frameworks (MOFs) are one class of crystalline adsorbent materials that are thought to have enormous potential in CO2 capture applications. In this research, the effect of changing the metal center between Zr(iv), Ce(iv), and Hf(iv), and the linker between BDC and PDC has been fully studied. Thus, the six UiO-66 isoreticular derivatives have been synthesized and characterized by FTIR, PXRD, TGA, and N2 adsorption. We also report the BET surface area, CO2 adsorption capacities, kinetics, and the adsorption isosteric heat (Q(st)) of the UiO-66 derivatives mentioned family. The CO2 adsorption kinetics were evaluated using pseudo-first order, pseudo-second order, Avrami's kinetic models, and the rate-limiting step with Boyd's film diffusion, interparticle diffusion, and intraparticle diffusion models. The isosteric heats of CO2 adsorption using various MOFs are in the range 20-65 kJ mol(-1) observing differences in adsorption capacities between 1.15 and 4.72 mmol g(-1) at different temperatures due to the electrostatic interactions between CO2 and extra-framework metal ions. The isosteric heat of adsorption calculation in this report, which accounts for the unexpectedly high heat released from Zr-UiO-66-PDC, is finally represented as an increase in the interaction of CO2 with the PDC linker and an increase in Q(st) with defects.
- ItemNovel pillar-layered metal organic frameworks based on pyrazole-carboxylate linkers for CO2 adsorption(2023) Lancheros Sánchez, Andrés Fernando; Schott Verdugo, Eduardo; Pontificia Universidad Católica de Chile. Facultad de Química y FarmaciaWith an increasing global population and energy requirement, the concentration of greenhouse gases, especially CO2, grows rapidly in the atmosphere. One of the solutions to mitigate this problem is to develop materials that can effectively capture and store CO2. The conventional method relies on using amine solvents to bind to CO2 chemically, but it is still not widely accepted because of the price of its regeneration. Porous solid materials such as Metal-Organic Frameworks (MOFs) have been suggested as CO2 adsorbents due to their-well defined molecular scale porosity, crystallinity, synthetic tunability, and high CO2 uptake capacity and selectivity. This Chemistry Ph.D. project first synthesized and characterized three novel carboxylate-pyrazole linkers (Ap, Bp, and Cp). Those linkers allowed the synthesis of novel MOFs using Zn(II)/Cu(II) metal nodes and 4,4’-bipyridine/DABCO pillaring linkers. Five MOFs were obtained, three from the Ap linker, one from Bp, and one from Cp. The carboxylate groups and pyridyl nitrogens are engaged in coordination bond formation with the metal node that propagates in generating 3D porous structures, and the pyrazole nitrogens remain free to interact with CO2. All the materials have shown excellent structural stability and crystallinity. The CO2 uptake was between 3.4-7.20% wt% at 273 K and 75 kPa. For Ap MOFs, changing the metal node from Zn(II) to Cu (II) and replacing the pillaring linker from 4,4’-bipyridine to DABCO makes it possible to increase CO2 adsorption. The isosteric enthalpy of adsorption (Hads) of CO2 adsorption for all of them was between 23-40 kJ/mol, making it more cost-effective for the MOF’s regeneration after CO2 storage. All five MOFs are good candidates for CO2 adsorption because of their stability, capture capabilities, and energy required for CO2 adsorption and regeneration.
- ItemSíntesis de productos químicos de alto valor agregado mediante reacciones One-Pot Tándem condensación/hidrogenación sobre catalizadores del tipo MOFS(2024) Pazo Carballo, César Alexander; Escalona Burgos, Néstor Guillermo; Schott Verdugo, Eduardo; Pontificia Universidad Católica de Chile. Escuela de QuímicaLa transformación catalítica de la biomasa se presenta como una ruta eficiente y selectiva para la generación de combustibles no convencionales y de productos químicos con valor agregado. El acoplamiento C-C de moléculas derivadas de la biomasa y posterior hidrogenación se ha planteado hoy día como una reto científico y novedoso. En este trabajo de tesis doctoral se estudió la actividad catalítica de las mallas metal-orgánicas (MOFs por sus siglas en inglés) sobre la condensación aldólica del benzaldehído y acetona sobre catalizadores mono- y bimetálicos-UiO-66 de Zr(IV), Hf(IV) y Ce(IV). Todos los catalizadores fueron sintetizados por el método solvotermal y se caracterizaron utilizando diversas técnicas analíticas. La actividad catalítica de las reacciones de condensación e hidrogenación se llevaron a cabo en un reactor discontinuo. Los resultados mostraron que la mayor actividad se observó sobre el Hf-UiO-66 debido al carácter oxofílico del metal, mostrando una mayor velocidad inicial de reacción para dar benzalacetona sin desactivar sus sitios activos. Efecto contrario se observó al cambiar el enlazador orgánico (ácido-2,5-piridin tereftálico) conllevando a cambios en la actividad catalítica y selectividad. En base a estos resultados, se seleccionó al Hf-UiO-66 como base del MOF con mejor potencial para su uso como soporte de las nanopartículas de ReOx- y ReOx-Pd. La caracterización fisicoquímica puso de manifiesto que las propiedades de estos materiales tras la adición con éxito de estas especies químicas, no alteró la cristalinidad del soporte microporoso. La evaluación catalítica de estos materiales en la hidrogenación de la benzalacetona mostró que todos presentan actividad catalítica con pequeñas variaciones en la selectividad hacia la formación de productos químicos de interés industrial. Finalmente, el ReOx-Pd/UiO-66 se evaluó en la reacción one-pot tándem condensación/hidrogenación mostrando actividad para ambas reacciones partiendo de la mezcla de sustratos benzaldehído/acetona.
- ItemSíntesis y caracterización de materiales porosos derivados del MOF-808 y UiO-67-NH2 con aplicación en catálisis heterogénea sobre derivados de la biomasa.(2025) Roa Gómez, Vanesa Belen; Schott Verdugo, Eduardo ; Pontificia Universidad Católica de Chile. Facultad de Química y FarmaciaResulta innegable que la humanidad ha desarrollado una marcada dependencia de los combustibles, principalmente el petróleo y los biocombustibles, como fuentes primarias para satisfacer nuestras necesidades energéticas. Este aumento progresivo en su utilización ha implicado el agotamiento acelerado de recursos naturales en conjunto de los efectos de contaminación ambiental. De este modo es prometedor el desarrollo de nuevas energías renovables y de combustibles alternativos a partir de derivados de la biomasa lignocelulósica, la cual mediante procesos de pretratamiento y fraccionamiento permite la separación de sus componentes para la formación de moléculas plataforma que son el inicio para la obtención de productos químicos de valor agregado. Algunas moléculas plataforma son el benzaldehído y catecol, los cuales permiten la obtención de productos como acetales y benzoquinonas, respectivamente, en presencia de un catalizador ácido, como ácidos minerales, siendo estos corrosivos y también perjudiciales para el medio ambiente. Para dar solución a esta problemática, ha sido relevante el estudio y desarrollo de catalizadores heterogéneos a partir de materiales porosos. Entre este tipo de catalizadores se encuentran las mallas metal-orgánicas o también conocidos como MOFs (del inglés Metal Organic Frameworks). Los MOFs son una subfamilia de los polímeros de coordinación (PC) que están formados por la unión de un clúster metálico y ligandos orgánicos. Los MOFs son materiales prometedores que presentan propiedades como alta cristalinidad, gran volumen de poro, gran área específica y gran tamaño de poros. Además, son materiales que pueden ser modificados estructuralmente lo cual permite ampliar las aplicaciones de estos materiales. Esta investigación se basa principalmente en la síntesis y caracterización de MOF808-M (siendo M: Zr(IV), Hf(IV) y Ce(IV)) y su posterior modificación post-sintética (PSM), adicionando sitios ácidos de Brønsted para dar origen a MOF-808-SO4-M. En segundo lugar, se propone la síntesis y caracterización de UiO-67-NH2-M y su PSM en presencia de 1,3-propanosultona para la formación de un catalizador con sitios ácidos Brønsted denominado, UiO-67-NH-SO3H-M. Estas estructuras serán caracterizadas estructuralmente mediante difracción de rayos X de polvo (PXDR), adsorción y desorción de nitrógeno, valoraciones potenciométricas ácido base, espectroscopía infrarroja (FT-IR) y mediante análisis termogravimétrico (TGA). Finalmente serán aplicados en pruebas catalíticas como acetalización de benzaldehído y la oxidación de catecol considerando el uso de reactivos comerciales.
- ItemSulfate-modified MOF-808 as a superacid catalyst: a performance evaluation of Zr(iv) and Hf(iv) analogues in acetalization reactions(2025) Roa Gómez, Vanesa Belen; Cea, Sebastián; Pazo Carballo, César Alexander; Llanos, Jaime; Olivares, Douglas; Escalona, Néstor; Leiva Campusano, Ángel; Hidalgo-Rosa, Yoan; Zarate, Ximena; Dongil, Ana Belén; Schott Verdugo, EduardoIn this study, we report the synthesis and characterization of MOF-808-SO4-M (M = Zr(IV), Hf(IV)), derived from MOF-808-M precursors. The introduction of sulfate groups enhances the Brønsted acidity of these materials, significantly improving their catalytic performance in the benzaldehyde acetalization reaction. The materials were characterized using powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), nitrogen adsorption–desorption analysis, thermogravimetric analysis (TGA), energy-dispersive spectroscopy (EDS), and Hammett indicator tests. Catalytic evaluation revealed that MOF-808-SO4-Zr exhibited significantly higher conversion compared to its Hf-based analogue, a difference attributed to its greater density of acid sites, as confirmed by temperature-programmed surface reaction (TPSR) analysis. These experimental results were further supported by density functional theory (DFT) calculations, which provided insights into the acidic properties and catalytic behavior of the materials.
- ItemThiophene- and bithiophene-based π-conjugated Schiff base oligomers containing binaphthalene moieties in the backbone. Properties and computational simulations(Royal Sociaty of Chemistry, 2024) González Guzmán, Alexis Fabián; Mariman Marchant, Andrea Paz; Hauyón Sepúlveda, René Alejandro; Pavéz Lizana, Danitza Belén; Saldías Barros, César Antonio; Schott Verdugo, Eduardo; Zarate, Ximena; García Paredes, Luis Enrique; Gonzalez-Henriquez, Carmen M.; Jessop, Ignacio A.; Tundidor Camba, Alain; Sobarzo Aucal, Patricio Antonio; Terraza Inostroza, ClaudioNew pi-conjugated Schiff base oligomers (o-AZdAN1Th and o-AZdAN2Th) based on a binaphthalene core and containing thiophene or bithiophene units in their backbone were synthesized from the reaction between [1,1 '-binaphthalene]-4,4 '-diamine with thiophene-2,5-dicarbaldehyde and [2,2 '-bithiophene]-5,5 '-dicarbaldehyde by a high-temperature polycondensation method. These new materials were slightly soluble in non-protic polar solvents, such as chloroform and dichloromethane. From GPC analysis of the CHCl3-soluble fraction, o-AZdAN1Th was found to be a tetramer, whereas o-AZdAN2Th was a trimer with 1.4 kDa and 1.3 kDa average molecular weight (Mn), respectively. Both samples exhibited high thermal stability with T5% values of 452 degrees C and 456 degrees C and relatively high Tg values of 346 degrees C and 384 degrees C, for o-AZdAN1Th and o-AZdAN2Th, respectively. The samples showed absorptions in the deep-blue (o-AZdAN1Th) and blue (o-AZdAN2Th) regions of the visible spectrum, and emission responses at 387 nm and 447 nm, respectively, with moderate Stokes shifts (77-95 nm). Their optical and electronic properties were similar to those described for thiophene-based materials, with optical bandgap values close to 2.4 eV. HOMO energy values of -5.98 and -5.95 eV and LUMO energy values of -3.87 eV and -3.84 eV were obtained for o-AZdAN1Th and o-AZdAN2Th, respectively. Theoretical DFT and TD-DFT calculations were used to compare the effect of increasing thiophene units along the backbone for the real and also theoretical o-AZdANxTh samples (x = 3 and 4 thiophene units). According to our study, these two new thiophene-based can be proposed for optoelectronic applications., Schiff base oligomers based on a binaphthalene core were synthesized from [1,1 '-binaphthalene]-4,4 '-diamine with thiophene-2,5-dicarbaldehyde and [2,2 '-bithiophene]-5,5 '-dicarbaldehyde by a high-temperature polycondensation method.
- ItemTunable optical properties of isoreticular UiO-67 MOFs for photocatalysis: a theoretical study(2024) Treto Suárez, Manuel A.; Hidalgo Rosa, Yoan; Saavedra Torres, Mario; Koivisto, Bryan D.; Mena Ulecia, Karel; Páez Hernández, Dayan; Zarate, Ximena; Schott Verdugo, EduardoA theoretical study of the reported photocatalytic systems based on Zr-based MOF (UiO-67) with biphenyl-4,4 '-dicarboxylic acid (bpdc) and 2,2 '-bipyridine-5,5 '-dicarboxylic acid (bpydc) as linkers was performed. Quantum chemical calculations were carried out to understand the optical properties of the materials and to facilitate the rational design of new UiO-67 derivatives with potentially improved features as photocatalysts under ambient conditions. Hence, the effect of the structural modifications on the optical properties was studied considering different designs based on the nature of the linkers: in 1 only the bpdc linker was considered, or the mixture 1 : 1 between bpdc and bpydc linkers (labeled as 1A). Also, substituents R, -NH2, and -SH, were included in the 1A MOF only over the bpdc linker (labeled as 1A-bpdc-R) and on both bpdc and bpydc linkers (labeled as 1A-R). Thus a family of six isoreticular UiO-67 derivatives was theoretically characterized using Density Functional Theory (DFT) calculations on the ground singlet (S0) and first excited states (singlet and triplet) using Time-Dependent Density Functional Theory (TD-DFT), multiconfigurational post-Hartree-Fock method via Complete Active Space Self-Consistent Field (CASSCF). In addition, the use of periodic DFT calculations suggest that the energy transfer (ET) channel between bpdc and bpydc linkers might generate more luminescence quenching of 1A when compare to 1. Besides, the results suggest that the 1A-R (R: -SH and NH2) can be used under ambient conditions; however, the ET exhibited by 1A, cannot take place in the same magnitude in these systems. These ET can favor the photocatalytic reduction of a potential metal ion, that can coordinate with the bpydc ligand, via LMCT transition. Consequently, the MOF might be photocatalytically active against molecules of interest (such as H2, N2, CO2, among others) with photo-reduced metal ions. These theoretical results serve as a useful tool to guide experimental efforts in the design of new photocatalytic MOF-based systems., A theoretical computational protocol was performed to understand the optical properties, the deactivation mechanisms, and the substituent effect for a photocatalytic MOF-based system.