
A. Rabdel Ruiz-SalvadorPablo de Olavide University | UPO · Department of Physical, Chemical and Natural Systems
A. Rabdel Ruiz-Salvador
PhD
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94
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Introduction
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January 1992 - December 2012
Publications
Publications (94)
Zeolite stability, in terms of lattice energy, is revisited from a crystal-chemistry point of view. A linearized equation relates the zeolite lattice energy using simple structural data readily available from experiments or modeling. The equation holds for a large range of zeolite energies, up to 3 eV per tetrahedron with respect to quartz, and has...
We have studied the clusters involved in the initial stages of nucleation of Zeolitic Imidazolate Frameworks, employing a wide range of computational techniques. In the pre-nucleating solution, the prevalent cluster is the ZnIm4 cluster (formed by a zinc cation, Zn2+, and four imidazolate anions, Im-), although clusters such as ZnIm3, Zn2Im7, Zn2Im...
We have studied the clusters involved in the initial stages of nucleation of Zeolitic Imidazolate Frameworks, employing a wide range of computational techniques. In the pre-nucleating solution, the prevalent cluster is the ZnIm4 cluster (formed by a zinc cation, Zn2+ , and four imidazolate anions, Im−), although clusters such as ZnIm3, Zn2Im5, Zn2I...
Ordered Nanoporous Metals (ONMs) form a new family of nanoporous materials composed only of pure metals. The expected impact is considerable from combining the ordered nanopore structure of MOFs, zeolites and carbon schwartzites with the robustness and electronic conductivity of metals. Little is known about their stability and structural features....
View of an Ordered Nanoporous Metal (ONM), a crystalline solid created by the gradual introduction of metal atoms within the pores of porous structures such as supertetrahedral solids and Metal-Organics Frameworks. Once these sacrificial templating structures are removed, we are left with porous metallic solids with an ordered arrangement of pores,...
The invasive alien seaweed Rugulopteryx okamurae (R.o.) has spread quickly through the Mediterranean Sea causing an unprecedented ecological impact. A solution integrated into a circular economy model is needed in order to curb the negative effects of its presence. Anaerobic digestion (AD) is proposed as a feasible process able to transform biomass...
Ethylene oxide is one of the most important raw materials in the chemical industry, with an annual production close to 35 million metric tons. Despite its importance, to date, no metal has been found that can compete with the original silver bulk material catalyst discovered in 1931. Recently, a few copper and copper-silver based nanostructures hav...
In this paper, we investigate the thermostructural properties of a type of silicon-based nanomaterials, which we refer to as SiC@Si nanocomposites, formed by SiC crystalline nanoparticles (with the cubic phase), embedded within an amorphous Si matrix. We have followed an in silico approach to characterize the mechanical and thermal behaviour of the...
Modeling zeolites structure including strongly interaction extra-framework species by using DFT is still a difficult task now a day. To face this problem, we have introduced here a simulated annealing (SA) method to obtain global minimum energies. This approximation has been applied to describing the structure of free common zeolites. Basically, th...
The whole compositional range (Ge$_f$ = Ge/(Ge+Si)= 0 to 1) of zeolite STW has been synthesized and studied by a comprehensive combined experimental--theoretical approach. The yield of zeolite goes through a maximum and then drops at the GeO$_2$ side of the series, following the inverse of the calculated free energy curve. The unit cell generally e...
The whole compositional range (Ge f = Ge/(Ge+Si)= 0 to 1) of zeolite STW has been synthesized and studied by a comprehensive combined experimental–theoretical approach. The yield of zeolite goes through a maximum and then drops at the GeO 2 side of the series, following the inverse of the calculated free energy curve. The unit cell generally expand...
The development of new interatomic potentials to model metallic systems is a difficult task, due in part to the dependence between the parameters that desbribe the electron density and the short-range interactions. The problem of finding adequate parameters becomes very complicated, and the iterative methods commonly employed to do that can get stu...
We introduce a method to allow the screening of large configurational spaces of heteroatom distributions in zeotype materials. Based on interatomic potential calculations of configurations containing up to three heteroatoms, we parameterize an atomistic effective Hamiltonian to describe the energy of multiple substitutions, with consideration of bo...
We report a new family of titanium–organic frameworks that enlarges the limited number of crystalline, porous materials available for this metal. They are chemically robust and can be prepared as single crystals at multi‐gram scale from multiple precursors. Their heterometallic structure enables engineering of their photoactivity by metal doping ra...
We report a new family of titanium–organic frameworks that enlarges the limited number of crystalline, porous materials available for this metal. They are chemically robust and can be prepared as single crystals at multi‐gram scale from multiple precursors. Their heterometallic structure enables engineering of their photoactivity by metal doping ra...
Atomic partial charges are parameters of key importance in the simulation of Metal-Organic Frameworks (MOFs), since Coulombic interactions decrease with the distance more slowly than van der Waals interactions. But despite its relevance, there is no method to unambiguously assign charges to each atom, since atomic charges are not quantum observable...
The conversion of ZIF-8 into ZIF-7 via post-synthetic modification with benzimidazole has been monitored quantifying the liberated 2-methylimidazole by chromatography. The reaction kinetics has been adjusted to the shrinking core model, providing the diffusion coefficient of bIm inside the pores and the reaction kinetic constant (2.86•10-7 cm²/s an...
Photocatalysts based on metal-organic frameworks (MOFs) are very promising due to a combination of high tuneability and convenient porous structure. Introducing porphyrin units within MOFs is a potential route to engineer these natural photosynthesis molecular catalysts into artificial photosynthesis heterogeneous catalysts. Using computer simulati...
The widespread emissions of toxic gases from fossil fuel combustion represent major welfare risks. Here we report the improvement of the selective sulfur dioxide capture from flue gas emissions of isoreticular nickel pyrazolate metal organic frameworks through the sequential introduction of missing-linker defects and extra-framework barium cations....
Supplementary Figures, Supplementary Tables, Supplementary Methods, Supplementary Notes and Supplementary References
We have carried out a geometry-based analysis of the need of artificial blocking in a collection of zeolites, for various gases of industrial and environmental relevance (carbon dioxide, methane, nitrogen, oxygen and argon), and we have studied its influence on the heats of adsorption and saturation uptakes, which are key properties for gas separat...
Tuning the electronic structure of metal–organic frameworks is the key to extending their functionality to the photocatalytic conversion of absorbed gases. Herein we discuss how the band edge positions in zeolitic imidazolate frameworks (ZIFs) can be tuned by mixing different imidazole-based linkers within the same structure. We present the band al...
Zeolithische Imidazolat-Gerüste: R. Grau-Crespo, S. Hamad et al. demonstrieren in ihrer Zuschrift auf S. 16246 ff., wie sich die Bandlücken und Bandkantenlagen in zeolithischen Imidazolat-Gerüsten durch die Verwendung von Linkermischungen gezielt einstellen lassen.
Zeolitic Imidazolate Frameworks: In their Communication on page 16012 ff., R. Grau-Crespo, S. Hamad et al. show that using mixed linkers within zeolitic imidazolate frameworks provides a route for tuning their electronic gaps and band edge positions.
Supplementary
Tuning the electronic structure of metal–organic frameworks is the key to extending their functionality to the photocatalytic conversion of absorbed gases. Herein we discuss how the band edge positions in zeolitic imidazolate frameworks (ZIFs) can be tuned by mixing different imidazole-based linkers within the same structure. We present the band al...
Controlling thermal expansion is an important, not yet resolved, and challenging problem in materials research. A conceptual design is introduced here for the first time, for the use of MOFs as platforms for controlling thermal expansion devices that can operate in the negative, zero and positive expansion regimens. A detailed computer simulation s...
Controlling thermal expansion is an important, not yet resolved, and challenging problem in materials research. A conceptual design is introduced here for the first time, for the use of MOFs as platforms for controlling thermal expansion devices that can operate in the negative, zero and positive expansion regimes. A detailed computer simulation st...
Incorporation of germanium in zeolites is well known to confer static flexibility to their framework, by stabilizing the formation of small rings. In this work, we show that the flexibility associated to Ge atoms in zeolites goes beyond this static effect, manifesting also a clear dynamic nature, in the sense that it leads to enhanced molecular dif...
Molecular valves are becoming popular for potential biomedical applications. However, little is known concerning their performance in energy and environmental areas. Zeolite RHO shows unique pore deformations upon changes in hydration, cation siting, cation type, or temperature-pressure conditions. By varying the level of distortion of double eight...
The algorithm automatically detects the rings of the structures (CIF, PDB, and CAR files) and performs statistics on them: area, structural distortions, ellipticities and characteristic distances. All the calculations are hard-coded.
To find optimal porous materials for adsorption-based separations is a challenging task due to the extremely large number of possible pore topologies and compositions. New porous material classes such as Metal Organic Frameworks (MOFs) are emerging, and hope to replace traditionally used materials such as zeolites. Computational screening offers re...
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 phen...
Molecular valves are becoming popular for potential biomedical applications. However, little is known concerning their performance in energy and environmental areas. Zeolite RHO shows unique pore deformations upon changes in hydration, cation siting, cation type, or temperature–pressure conditions. By varying the level of distortion of double eight...
The thermostructural properties of Ni-Cr materials, as bulk and nanoparticle (NP) systems, have been predicted with a newly developed interatomic potential, for Ni/Cr ratios from 100/0 to 60/40. The potential, which has been fitted using experimental data and further validated using Density Functional Theory (DFT), describes correctly the variation...
Abstract Atomic partial charges are parameters of key importance in the simulation of Metal–Organic Frameworks (MOFs), since Coulombic interactions decrease with the distance more slowly than van der Waals interactions. But despite its relevance, there is no method to unambiguously assign charges to each atom, since atomic charges are not quantum o...
The GCMC simulation of CO2 adsorption in MOF-5 is revisited, finding a surprising role of the BDC organic ligand in this process. A novel structure partition methodology is introduced to decompose the relative contributions of the metal oxoclusters and the organic ligands. The origin of the primary step in the CO2 adsorption isotherm in MOF-5 is ex...
Four coordination networks based on the {ε-PMo(V)(8)Mo(VI)(4)O(40)(OH)(4)Zn(4)} Keggin unit (εZn) have been synthesized under hydrothermal conditions. (TBA)(3){PMo(V)(8)Mo(VI)(4)O(36)(OH)(4)Zn(4)}[C(6)H(4)(COO)(2)](2) (ε(isop)(2)) is a 2D material with monomeric εZn units connected via 1,3 benzenedicarboxylate (isop) linkers and tetrabutylammonium...
We have calculated the concentrations of Mg in the bulk and surfaces of aragonite CaCO(3) in equilibrium with aqueous solution, based on molecular dynamics simulations and grand-canonical statistical mechanics. Mg is incorporated in the surfaces, in particular in the (001) terraces, rather than in the bulk of aragonite particles. However, the total...
Chemical insertion and de-insertion of lithium in pellet samples of the solid solutions Pr0.5+x-yLi0.5-3xBiy square 2xTiO3 were studied. Two regions of the phase diagram are studied: one having constant composition of bismuth and the other of lithium. The amount of inserted lithium depends on both the number of vacancies and the amount of bismuth i...
In the present work a combination of chemically constrained Rietveld refinement and computer simula-tion is used for the determination of the positions of the extra-framework cations Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ in the channels of clinoptilolite. The analysis of the metal rich clinoptilolites with two different Si/Al ratio (4.7 and 7.8) demonstr...
The step-wise dealumination of a natural clinoptilolite has been achieved through a new milder treatment, comprising cycles of aqueous solutions of hydrochloric acid with washing steps. The course of the dealumination was monitored by XRD, FTIR, TGA, UV-vis-DRS and NMR. The XRD patterns show a contraction of cell volume during progressive dealumina...
We investigate here a new family of zeolitic Metal Organic Frameworks (MOFs) based on imidazole (im) as the ligand and epsilon-type Keggin PolyOxoMetalates (POMs) as building units. The POM used in this study is the epsilon-{PMo(12)O(40)} Keggin isomer capped by four Zn(ii) ions (noted epsilon-Zn) in tetrahedral coordination. We describe here our m...
a b s t r a c t The step-wise dealumination of a natural clinoptilolite has been achieved through a new milder treat-ment, comprising cycles of aqueous solutions of hydrochloric acid with washing steps. The course of the dealumination was monitored by XRD, FTIR, TGA, UV–vis-DRS and NMR. The XRD patterns show a contraction of cell volume during prog...
The location of extra-framework cations in low-silica zeolites is determined from in-house X-ray powder diffraction pattern by a successful implementation of a newly developed methodology. The method combines reciprocal and direct space methods plus a cost function that accounts for simultaneous fit of the chemical composition and the X-ray diffrac...
The location of extra-framework cations in low-silica zeolites is determined from in-house X-ray powder diffraction pattern by a successful implementation of a newly developed methodology. The method combines reciprocal and direct space methods plus a cost function that accounts for simultaneous fit of the chemical composition and the X-ray diffrac...
We have investigated the thermodynamics of mixing between aragonite (orthorhombic CaCO(3)) and strontianite (SrCO(3)). In agreement with experiment, our simulations predict that there is a miscibility gap between the two solids at ambient conditions. All Sr(x)Ca(1-x)CO(3) solids with compositions 0.12 < x < 0.87 are metastable with respect to separ...
The targeted design and simulation of a new family of zeolitic metal-organic frameworks (MOFs) based on benzenedicarboxylate (BDC) as the ligand and epsilon-type Keggin polyoxometalates (POMs) as building units, named here Z-POMOFs, have been performed. A key feature is the use of the analogy between the connectivity of silicon in dense minerals an...
We use periodic DFT calculations to compute the total energy of known zeolitic imidazole frameworks (ZIFs) together with those of hypothetical porous ZIFs. We show that the total energy of ZIFs decreases with increasing density, in a similar fashion to the alu-mino-silicate zeolites, but with a more complex energy landscape. The computational evalu...
Considering the biological properties reported for the purified natural clinoptilolite, NZ, we prepared K- and Li-enriched forms aimed at release matrices for biomedical applications. The raw material and the obtained solid samples were characterized by means of atomic absorption spectroscopy, X-ray diffraction, 27Al and 29Si MAS nuclear magnetic r...
A method has been developed for separation of ionic and electronic conductivity in mixed conductors. The procedure is accomplished by using blocking electrodes and the Kramers–Kronig relations for separating the dc conductivity from total response. This method was applied to lithium inserted and deinserted sample of Pr0.56Bi0.04Li0.2TiO3. This mate...
Computational methods are described that model accurately the structure of hydrated Ca-bearing zeolites. Using Goosecreekite as a model system we probe the influence of framework ordering, cation siting and hydration of pores on the structure and its stability. We develop a methodology which allows the location of Al within the framework to be dete...
A methodology, based on a combination of Molecular Dynamics, Monte Carlo and Energy Minimization techniques, has been developed for determining the distribution of mobile ions in heavily defective oxides. We present its application to a superionic lithium lanthanum titanate perovskite, that shows how the lattice A sites become segregated into two s...
Periodic cell lattice energy calculations are used to Study isolated Si atoms and small islands in SAPO-31. The unique zigzag shape of the main channel provides considerable flexibility. We find that isolated acid sites preferentially occupy the O4 sites, whilst O2 and O3 are preferred when islands are considered.
Unter Hochdruck: Computermodellierungen sagen voraus, dass das natürliche Zeolith Laumontit druckinduziert hydratisiert wird. Das wasserarme Analogon Leonhardit wandelt sich in die vollständig hydratisierte Laumontitstruktur um (siehe Bild), ein Prozess mit signifikanter geochemischer Bedeutung. Mit den erarbeiteten Modellen und Methoden lässt sich...
We present the results of computer modelling studies of the effect of hydration levels and pressure on a
series of important natural zeolites. We show how our methods and models are able to reproduce the distinct
dehydration behaviour of the isostructural minerals natrolite and scolecite. Furthermore, we are able to show
how laumontite can readily...
Dielectric spectroscopy (DS) techniques play a major role in gaining
insight into important peculiarities of dielectric responses of
materials. The principles of DS of solids are discussed starting from
simple concepts. The physical basis is presented, emphasizing the
meaning of the magnitudes and phenomena involved, including the
microscopic aspec...
The use of porous materials as host systems for medical applications has been considered in recent years. Taking into account the biological properties reported for the purified natural clinoptilolite, NZ, we study here the influence of different treatments on the structural behavior of the raw material, aiming at the future preparation of slow rel...
Taking into account the biological properties of the purified natural clinoptilolite, NZ, some studies were conducted to evaluate the physicochemical interaction between this zeolite and two drugs, metronidazole and sulfamethoxazole, which cause considerable gastric side effects. Two modified forms of NZ were also considered. We have studied the dr...