- I am a material scientist, working on computational physical chemistry with emphasis on porous materials (MOFs, COFs,... moreI am a material scientist, working on computational physical chemistry with emphasis on porous materials (MOFs, COFs, coordination polymers and zeolites) and with strong collaboration with experimentalists. I created the first approach for the automatic design of porous solids based on topological templates (Tobunporousedit
Classical calculations using the shell model were performed to study the stability, distribution, structure and acid strength of active centers in H-ZSM-5 catalyst. The defect energies associated with Al/Si substitution, in the absence of... more
Classical calculations using the shell model were performed to study the stability, distribution, structure and acid strength of active centers in H-ZSM-5 catalyst. The defect energies associated with Al/Si substitution, in the absence of proton or other counterions, were calculated for the 24 crystallographically nonequivalent T sites of the monoclinic structure of ZSM-5, and the lattice energies of the 96 structures obtained by periodic (Al, H)/Si substitutions in all di† erent positions of the framework were also calculated. Proton ...
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In this paper we deal with the incorporation of Fe 3+ into the framework of AlPO 4 -5. Calculations were performed using energy minimization techniques. Two cases were taken into account: one Fe 3+ ion in the full unit cell (Al 3+ /Fe 3+... more
In this paper we deal with the incorporation of Fe 3+ into the framework of AlPO 4 -5. Calculations were performed using energy minimization techniques. Two cases were taken into account: one Fe 3+ ion in the full unit cell (Al 3+ /Fe 3+ =23/1) and one Fe 3+ in the asymmetric unit cell ...
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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... more
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. Here we address these points to provide clues toward their rational synthesis, introducing an automatic atomistic design that uses model building and molecular dynamics structural relaxation, and is validated against the experimentally known ONMs. Analysing the properties of the 10 stable structures out of the 17 studied (14 of which are designed in this work) using four noble metals (Pt, Pd, Au and Ag), we have deciphered some key elements and structural descriptors that provide guidelines for the experimental synthesis of ONMS. The long-lived metastability of the stable ONMs is evidenced by the high free energy landscape, computed via Metadynamic simulations. The new ONMs permit molecular diffusion of various molecules of industrial relevance, increasing the expectation for their use in catalysis, separation, nanofiltration, batteries, fuel cells, etc. Stable low-cost ONMs are predicted using Earth-abundant Ni metal, which maintains the main features of their relative noble metal forms.
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This work shows the synthesis and reaction monitoring of different ZIF-7/8 core–shells and their application in MMMs for CO2 separation.
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The distribution of aluminium within the lattice of a model calcium heulandite is considered. Signicant segregation of Al to particular sites is noted with T2 being preferentially occupied whereas T4 has a low Al occupancy. T5 is also... more
The distribution of aluminium within the lattice of a model calcium heulandite is considered. Signicant segregation of Al to particular sites is noted with T2 being preferentially occupied whereas T4 has a low Al occupancy. T5 is also occupied, in contrast to earlier work on ...
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... A. Rabdel Ruiz-Salvador*a, Ariel Gómeza, Dewi W. Lewis*b, C. Richard A. Catlowc, L. Marleny Rodríguez-Albeloa, Luis ... imre.oc.uh.cu. b Centre for Theoretical and Computational Chemistry, Department of Chemistry, University College... more
... A. Rabdel Ruiz-Salvador*a, Ariel Gómeza, Dewi W. Lewis*b, C. Richard A. Catlowc, L. Marleny Rodríguez-Albeloa, Luis ... imre.oc.uh.cu. b Centre for Theoretical and Computational Chemistry, Department of Chemistry, University College London, 20 Gordon St., London, UK ...
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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 two heteroatoms per cell, we... more
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 two heteroatoms per cell, we parameterize an atomistic effective Hamiltonian to describe the energy of multiple substitutions, with consideration of both short- and long-range interactions. Then, the effective Hamiltonian is used to explore the full configurational space at other compositions, allowing the identification of the most stable structures for further analysis. We illustrate our approach with the aluminogermanate PKU-9, where we show that increasing the aluminium concentration changes the likely siting of Al, in agreement with experiment.
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ABSTRACT 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... more
ABSTRACT 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 release systems. In particular, we study by 27Al, 29Si, 23Na MASNMR, and 13C CP-MAS-NMR the evolution of these elements on clinoptilolite after acid treatments, and modifications involving a surfactant and three drugs. Our results confirm a small presence of octahedral aluminum, when NZ and AZ (Na-clinoptilolite) are submitted to modifications at pH 1.2, and also that a measurable amount of organic molecules incorporates to the clinoptilolite after adequate treatments. Finally, we study the influence of the treatments on the specific surface area of NZ through the use of the BET technique based on nitrogen adsorption.
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Ge substitution for Si in zeolites containing double-four-membered rings is far more complex than thought.
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... more
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 rather than by linker functionalization. Compared to other methodologies based on the post-synthetic metallation of MOFs, our approach is well-fitted for controlling the positioning of dopants at an atomic level to gain more precise control over the band-gap and electronic properties of the porous solid. Changes in the band-gap are also rationalized with computational modelling and experimentally confirmed by photocatalytic H production.
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The development of new interatomic potentials to model metallic systems is a difficult task, due in part to the dependence between the parameters that describe the electron density and the short-range interactions. Parameter search... more
The development of new interatomic potentials to model metallic systems is a difficult task, due in part to the dependence between the parameters that describe the electron density and the short-range interactions. Parameter search methods are prone to false convergence. To solve this problem, we have developed a methodology for obtaining the electron density parameters independently of the short-range interactions, so that physically sound parameters can be obtained to describe the electron density, after which the short-range parameters can be fitted, thus reducing the complexity of the process and yielding better interatomic potentials. With the new method we can develop self-consistent, accurate force fields, using solely calculations, without the need to fit to experimental data. Density functional theory calculations are used to compute the observables with which the potential is fit. We applied the method to a Ni-based Inconel 625 superalloy (IN625), modelled here as Ni, Cr, ...
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Computer simulations show that iron substitution at the octahedral centres of porphyrin-based metal–organic frameworks leads to optimal band structures for photocatalysis.
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Density functional theory calculations reveal that the electronic structure of a family of porphyrin-based metal–organic frameworks is suitable for the photocatalysis of water splitting and carbon dioxide reduction reactions.
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Static lattice simulations are presented on the microporous aluminophosphate AlPO4-5. Minimisation methods together with lattice dynamical calculations are able to identify stable minima for the structure. We show, in agreement with the... more
Static lattice simulations are presented on the microporous aluminophosphate AlPO4-5. Minimisation methods together with lattice dynamical calculations are able to identify stable minima for the structure. We show, in agreement with the recent work of Henson et al., that reduction of the symmetry of the structure from P6cc to P6 leads to the relaxation of Al-O-P angles from the linear structure reported in earlier crystallographic structures. We find that the orthorhombic space group Pcc2 suggested recently by Mora et al. has only a very slightly higher energy than that calculated for the P6 structure. Differences in bond lengths and angles between the two structures are correspondingly small. We find that the inclusion of a representation of the polarisability of the oxygen in the potential model is essential in removing the linear Al-O-P angles in the simulated structures.
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ABSTRACT 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... more
ABSTRACT 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 drug solutions before and after the contact with the zeolitic materials in a wide range of pH values by UV spectroscopy. The structure of the two drugs remains unaltered after interaction with the zeolitic products. It is demonstrated that metronidazole adsorption by the different materials is small in acidic pH, and that the zeolitic materials studied do not adsorb sulfamethoxazole at the considered pH values. The overall study suggests the possibility of parallel administration of these products. These results are coherent with a complementary investigation by transmission IR spectroscopy about the possible incorporation of drug on NZ and its modified forms.
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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... more
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 ...
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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)... more
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 relatively fast searching for candidate structures as well as side-by-side comparisons between material families. This work is pioneering at examining the families comprised by the experimentally known zeolites and their respective Zeolitic Imidazolate Framework (ZIF) counterparts in the context of a number of environmental and industrial separations involving carbon dioxide, nitrogen, methane, oxygen, and argon. Additionally, unlike related published work, here all the targeted structures have been previously relaxed through energy minimization. On the first level of characterization, we considered a detailed pore characterization, identifying 24 zeolites as promising candidates for gas separation based on adsorbate sizes. The second level involved interatomic potential-based calculations to assess the adsorption performance of the materials. We found no correlation in the values of heat of adsorption between zeolites and ZIFs sharing the same topology. A number of structures were identified as potential experimental targets for CO2/N2, and CO2/CH4 affinity-based separations.
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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... more
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 with temperature of lattice parameters and the coefficient of thermal expansion, from 100 K to 1000 K. Using this potential, we have performed Molecular Dynamics (MD) simulations on bulk Ni-Cr alloys of various compositions, for which no experimental data are available. Similarly, NPs with diameters of 3, 5, 7, and 10 nm were studied. We found a very rapid convergence of NP properties with the size of the systems, showing already the 5 nm NPs with a thermostructural behaviour similar to the bulk. MD simulations of two 5 nm NPs show very little sintering and thermally induced damage, for temperatures between 300 K and 1000 K, suggesting that materials formed by agglomeration of Ni-Cr NPs meet the thermostructural stability requirements for catalysis applications.