Desenvolvimento de membranas para separação de gases contendo MOFs (metal organic frameworks)

Disserta ção apresentada para obten ção do Grau de Mestre em Engenharia Química e Bioquímica

Síntese e caracterização de MOFs – Metal Organic Frameworks

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

Preparação de novas membranas com MOF’s para aplicação em processos de captura de CO2

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

Preparação de novas membranas com MOF’s e líquidos iónicos para aplicação em processos de captura de CO2

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

First examples of aliphatic zirconium MOFs and their influence of inorganic anions on their crystal structures

Aus: CrystEngComm, Vol. 17.2015, H. 2, S. 331-337

Metalosupramoléculas discretas e Metal Organic Frameworks (MOFs) baseados em íons lantanídeos: design, síntese, caracterização e propriedades

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Paving the way for methane hydrate formation on metal–organic frameworks (MOFs)

The presence of a highly tunable porous structure and surface chemistry makes metal–organic framework (MOF) materials excellent candidates for artificial methane hydrate formation under mild temperature and pressure conditions (2 °C and 3–5 MPa). Experimental results using MOFs with a different pore structure and chemical nature (MIL-100 (Fe) and ZIF-8) clearly show that the water–framework interactions play a crucial role in defining the extent and nature of the gas hydrates formed. Whereas the hydrophobic MOF promotes methane hydrate formation with a high yield, the hydrophilic one does not. The formation of these methane hydrates on MOFs has been identified for the first time using inelastic neutron scattering (INS) and synchrotron X-ray powder diffraction (SXRPD). The results described in this work pave the way towards the design of new MOF structures able to promote artificial methane hydrate formation upon request (confined or non-confined) and under milder conditions than in nature.

Birefringence enhancement by using D-shaped microstructured optical fibers

In this study, a detailed numerical investigation is presented, seeking to enhance the birefringence effect by using D-shaped microstructured optical fibers (MOFs). We studied a D-shape core geometry associated with three different air-hole configurations: circular and elliptical, aligned with either the x-direction or the y-direction. Results have shown that ultrahigh birefringence MOFs, with B values of the order of 10(-2) for a wide range of wavelengths, can be obtained. The highest birefringence B was equal 3.97 x 10(-2), a value found for a D-MOF (circular holes) at 1550 nm. To the best of our knowledge, this is the highest theoretical value in the published literature.

Síntese e caracterização de redes metalo-orgânicas de fármacos

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Química e Biológica

Greener Selective Cycloalkane Oxidations with Hydrogen Peroxide Catalyzed by Copper-5-(4-pyridyl)tetrazolate Metal-Organic Frameworks

Microwave assisted synthesis of the Cu(I) compound [Cu(µ4-4-ptz)]n [1, 4-ptz = 5-(4-pyridyl)tetrazolate] has been performed by employing a relatively easy method and within a shorter period of time compared to its sister compounds. The syntheses of the Cu(II) compounds [Cu3(µ3-4-ptz)4(µ2-N3)2(DMF)2]n∙(DMF)2n (2) and [Cu(µ2-4-ptz)2(H2O)2]n (3) using a similar method were reported previously by us. MOFs 1-3 revealed high catalytic activity toward oxidation of cyclic alkanes (cyclopentane, -hexane and -octane) with aqueous hydrogen peroxide, under very mild conditions (at room temperature), without any added solvent or additive. The most efficient system (2/H2O2) showed, for the oxidation of cyclohexane, a turnover number (TON) of 396 (TOF of 40 h−1), with an overall product yield (cyclohexanol and cyclohexanone) of 40% relative to the substrate. Moreover, the heterogeneous catalytic systems 1–3 allowed an easy catalyst recovery and reuse, at least for four consecutive cycles, maintaining ca. 90% of the initial high activity and concomitant high selectivity.

Upgrade of an experimental volumetric unit for gas adsorption equilibrium studies

In this work, a volumetric unit previously assembled by the research group was upgraded. This unit revamping was necessary due to the malfunction of the solenoid valves employed in the original experimental setup, which were not sealing the gas properly leading to erroneous adsorption equilibrium measurements. Therefore, the solenoid valves were substituted by manual ball valves. After the volumetric unit improvement its operation was validated. For this purpose, the adsorption equilibrium of carbon dioxide (CO2) at 323K and 0 - 20 bar was measured on two different activated carbon samples, in the of extrudates (ANG6) and of a honeycomb monolith (ACHM). The adsorption equilibrium results were compared with data previously measured by the research group, using a high-pressure microbalance from Rubotherm GmbH (Germany) – gravimetric. The results obtained using both apparatuses are coincident thus validating the good operation of the volumetric unit upgraded in this work. Furthermore, the adsorption equilibrium of CO2 at 303K and 0 - 10 bar on Metal-Organic Frameworks (MOFs) Cu-BTC and Fe-BTC was also studied. The CO2 adsorption equilibrium results for both MOFs were compared with the literature results showing good agreement, which confirms the good quality of the experimental results obtained in the new volumetric unit. Cu-BTC sample showed significantly higher CO2 adsorption capacity when compared with the Fe-BTC sample. The revamping of the volumetric unit included a new valve configuration in order to allow testing an alternative method for the measurement of adsorption equilibrium. This new method was employed to measure the adsorption equilibrium of CO2 on ANG6 and ACHM at 303, 323 and 353K within 0-10 bar. The good quality of the obtained experimental data was testified by comparison with data previously obtained by the research group in a gravimetric apparatus.

Disseny i optimització de membranes compòsit amb xarxes metal•loorgàniques per a nanofiltració i separacions de gasos

Projecte de recerca elaborat a partir d’una estada a la Katholieke Universiteit Leuven, Belgium, entre 2007 i 2009. Aquest projecte descriu la síntesi i aplicació de nous tipus de membranes compòsit basades en xarxes metal•loorgàniques (MOFs). Aquestes es van seleccionar tenint en compte les seves propietats estructurals per tal de discriminar les espècies a separar en funció de la seva mida molecular. Les membranes obtingudes s'han aplicat satisfactòriament tant en separacions líquides, concretament en nanofiltració resistent a dissolvents (SRNF), i en separació de parells de gasos com CO2/CH4, CO2/N2 i H2/CO2. Els resultats obtinguts posen de manifest l'obtenció de membranes sense defectes i amb rendiments prometedors, en la majoria dels casos, amb permeabilitats i selectivitats superiors a membranes purament polimèriques. Tanmateix s'ha desenvolupat un nou equipament d'alt rendiment (HT) per a separacions de gasos que inclou un mòdul que permet realitzar 16 experiments simultàniament. Els resultats obtinguts amb el nou equip són comparables amb els obtinguts amb mòduls convencionals, i alhora presenten una millor reproduïbilitat. Finalment, s'ha establert un nou mètode per a obtenir membranes per a SRNF, que han estat aplicades en processos de separació de catalitzadors homogenis en dissolvents polars apròtics i s'han caracteritzat emprant la tècnica d'espectroscòpia d'annihilació de positrons, que ha permès establir per primer cop una relació entre les propietats estructurals de les membranes a nivell molecular i el seu rendiment en les aplicacions anteriors.

Redes metalorgânicas e suas aplicações em catálise

Metal-organic frameworks (MOFs) form a new class of materials with well-defined yet tunable properties. These are crystalline, highly porous and exhibit strong metal-ligand interactions. Importantly, their physical and chemical properties, including pore size, pore structure, acidity, and magnetic and optical characteristics, can be tailored by choosing the appropriate ligands and metal precursors. Here we review the key aspects of synthesis and characterization of MOFs, focusing on lanthanide-based and vanadium-based materials. We also outline some of their applications in catalysis and materials science.

Mechanistic insights into a gas–solid reaction in molecular crystals: the role of hydrogen bonding

Reactions in (molecular) organic crystalline solids have been shown to be important for exerting control that is unattainable over chemical transformations in solution. Such control has also been achieved for reactions within metal– organic cages. In these examples, the reactants are already in place within the crystals following the original crystal growth. The post-synthetic modification of metal–organic frameworks (MOFs and indeed reactions and catalysis within MOFs have been recently demonstrated; in these cases the reactants enter the crystals through permanent channels. Another growing area of interest within molecular solid-state chemistry is synthesis by mechanical co-grinding of solid reactants—often referred to as mechanochemistry. Finally, in a small number of reported examples, molecules also have been shown to enter nonporous crystals directly from the gas or vapor phase, but in only a few of these examples does a change in covalent bonding result, which indicates that a reaction occurs within the nonporous crystals. It is this latter type of highly uncommon reaction that is the focus of the present study.

Electronic structure of porphyrin-based metal-organic frameworks and their suitability for solar fuel production photocatalysis

Metal-organic frameworks (MOFs) can be exceptionally good catalytic materials thanks to the presence of active metal centres and a porous structure that is advantageous for molecular adsorption and confinement. We present here a first-principles investigation of the electronic structure of a family of MOFs based on porphyrins connected through phenyl-carboxyl ligands and AlOH species, in order to assess their suitability for the photocatalysis of fuel production reactions using sunlight. We consider structures with protonated porphyrins and those with the protons exchanged with late 3d metal cations (Fe2+, Co2+, Ni2+, Cu2+, Zn2+), a process that we find to be thermodynamically favorable from aqueous solution for all these metals. Our band structure calculations, based on an accurate screened hybrid functional, reveal that the bandgaps are in a favorable range (2.0 to 2.6 eV) for efficient adsorption of solar light. Furthermore, by approximating the vacuum level to the pore center potential, we provide the alignment of the MOFs’ band edges with the redox potentials for water splitting and carbon dioxide reduction, and show that the structures studied here have band edges positions suitable for these reactions at neutral pH.