Dewi W. Lewis

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Organization: University College London , England
Department: Department of Chemistry
Title: (PhD)
Co-reporter:Michael Schauperl and Dewi W. Lewis
The Journal of Physical Chemistry B 2015 Volume 119(Issue 2) pp:563-571
Publication Date(Web):December 19, 2014
DOI:10.1021/jp506157x
We devised a strategy, using a de novo building approach, to construct model molecularly imprinted polymers (MIPs) and assess their ability at binding various target molecules. While our models successfully reproduce the gross experimental selectivities for two xanthines, our atomistic models reveal in detail the considerable heterogeneity of the structure and binding mechanisms of different imprints within such a material. We also demonstrate how nonimprinted regions of a MIP are also responsible for much of binding of target molecules. High levels of cross-linking are shown to produce less specific imprints.
Co-reporter:Rafael A. Sarmiento-Perez, L. Marleny Rodriguez-Albelo, Ariel Gomez, Miguel Autie-Perez, Dewi W. Lewis, A. Rabdel Ruiz-Salvador
Microporous and Mesoporous Materials 2012 Volume 163() pp:186-191
Publication Date(Web):15 November 2012
DOI:10.1016/j.micromeso.2012.07.011
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 explained by a synergistic effect arising from specific short-range interactions between the sorbate and the MOF components with equal contributions from both the metal oxocluster and the organic ligand, together with an additional contribution due to the nano-confinement of the adsorbate.Graphical abstractHighlights► CO2 adsorption in MOF5 is revisited looking for the role (if any) of the BDC. ► A novel structure partition strategy is introduced to achieve the proposed goal. ► Grand Canonical Monte Carlo simulation are used for modeling the CO2 adsorption. ► A substantial role is indentified for BDC in the CO2 adsorption on MOF5.
Co-reporter:Yunier Garcia-Basabe, Inocente Rodriguez-Iznaga, Louis-Charles de Menorval, Philip Llewellyn, Guillaume Maurin, Dewi W. Lewis, Russell Binions, Miguel Autie, A. Rabdel Ruiz-Salvador
Microporous and Mesoporous Materials 2010 Volume 135(1–3) pp:187-196
Publication Date(Web):November 2010
DOI:10.1016/j.micromeso.2010.07.008
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 dealumination steps and a decrease in crystallinity after the third dealumination cycle. The framework and OH vibrations in FTIR spectra show progressive extraction of aluminum atoms from zeolite framework and consequently the formation of silanol nests. 27Al MAS NMR indicates that low levels of octahedral aluminum species are created during the treatments.
Co-reporter:Miguel J. Mora-Fonz, C. Richard A. Catlow and Dewi W. Lewis  
Physical Chemistry Chemical Physics 2008 vol. 10(Issue 43) pp:6571-6578
Publication Date(Web):25 Sep 2008
DOI:10.1039/B719632F
The relative strength of water–water, water–silicate and silicate–silicate interactions are studied, in order to explain the low solubility of the monomer (Si(OH)4), and determine the degree of dispersion of silicate clusters in solution during the hydrothermal synthesis of zeolites. We will show how the hydrogen bond interactions between water and monomeric silicate species are similar to that in pure water, whilst monomer–monomer interactions are stronger. However, when larger silicate species are also considered we find the relative hydrogen-bonding strength to follow: water–water < silicate–water < silicate–silicate. The effects of pH are also considered. The implications of the relative strength of these interactions on the formation of larger silicate species, leading to zeolite pre-nucleation, are discussed.
Co-reporter:A. Rabdel Ruiz-Salvador, Neyvis Almora-Barrios, Ariel Gómez and Dewi W. Lewis  
Physical Chemistry Chemical Physics 2007 vol. 9(Issue 4) pp:521-532
Publication Date(Web):07 Dec 2006
DOI:10.1039/B607030B
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 determined together with the position of extra-framework cations, in a stepwise fashion, progressing from an anhydrous model, via a dielectric continuum model, to finally, a fully atomistic model of the water in the intrazeolite pore space. Our methods reveal the complex interplay of short- and long-range interactions on the optimal structure of such materials.
Co-reporter:Miguel J. Mora-Fonz;C. Richard A. Catlow
Angewandte Chemie 2005 Volume 117(Issue 20) pp:
Publication Date(Web):13 APR 2005
DOI:10.1002/ange.200462524

Wesentliche der Keimbildung vorausgehende Spezies bei der Zeolithbildung sind nach Dichtefunktionalrechnungen beispielsweise ein offenkettiges Tetramer und ein viergliedriger Ring (siehe Bild). Die Bedeutung von Lösungsmittel und pH-Wert für die Steuerung von Kondensationsreaktionen, vor allem wenn sie die Bildung der in vielen Zeolithstrukturen vorhandenen cyclischen Strukturen begünstigen, wird bestätigt.

Co-reporter:Miguel J. Mora-Fonz;C. Richard A. Catlow
Angewandte Chemie International Edition 2005 Volume 44(Issue 20) pp:
Publication Date(Web):13 APR 2005
DOI:10.1002/anie.200462524

Key prenucleation species like the open-chain tetramer and the four-membered-ring structure shown are implicated in the formation of zeolites according to density functional theory calculations. The role of the solvent and the pH value is confirmed in the control of condensation reactions, particularly those favoring the formation of cyclic structures present in many zeolite structures.

Co-reporter:Catherine L. I. M. White;A. Rabdel Ruiz-Salvador Dr.
Angewandte Chemie International Edition 2004 Volume 43(Issue 4) pp:
Publication Date(Web):14 JAN 2004
DOI:10.1002/anie.200352364

Computer modeling methods predict that the natural zeolite laumontite will undergo pressure-induced hydration. Specifically, the water-poor analogue “leonhardite” transforms to the fully hydrated laumontite structure (see picture), a transformation with significant geochemical impact. The models and methodologies employed are also capable of replicating the observed dehydration behavior of laumontite.

Co-reporter:Catherine L. I. M. White;A. Rabdel Ruiz-Salvador Dr.
Angewandte Chemie 2004 Volume 116(Issue 4) pp:
Publication Date(Web):14 JAN 2004
DOI:10.1002/ange.200352364

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 auch die beobachtete Dehydratisierung von Laumontit erklären.

Co-reporter:Tanya Gibbs and Dewi W. Lewis  
Chemical Communications 2002 (Issue 22) pp:2660-2661
Publication Date(Web):11 Oct 2002
DOI:10.1039/B207505A
Simultaneous occupation of adjacent SI (or SIa) and SI′ sites is calculated to be favourable in dehydrated zeolite K-LSX (supporting the experimental work of Paillaud et al.), although such a configuration is unlikely in other dehydrated LSX zeolites.
Co-reporter:Miguel J. Mora-Fonz, C. Richard A. Catlow and Dewi W. Lewis
Physical Chemistry Chemical Physics 2008 - vol. 10(Issue 43) pp:NaN6578-6578
Publication Date(Web):2008/09/25
DOI:10.1039/B719632F
The relative strength of water–water, water–silicate and silicate–silicate interactions are studied, in order to explain the low solubility of the monomer (Si(OH)4), and determine the degree of dispersion of silicate clusters in solution during the hydrothermal synthesis of zeolites. We will show how the hydrogen bond interactions between water and monomeric silicate species are similar to that in pure water, whilst monomer–monomer interactions are stronger. However, when larger silicate species are also considered we find the relative hydrogen-bonding strength to follow: water–water < silicate–water < silicate–silicate. The effects of pH are also considered. The implications of the relative strength of these interactions on the formation of larger silicate species, leading to zeolite pre-nucleation, are discussed.
Co-reporter:A. Rabdel Ruiz-Salvador, Neyvis Almora-Barrios, Ariel Gómez and Dewi W. Lewis
Physical Chemistry Chemical Physics 2007 - vol. 9(Issue 4) pp:NaN532-532
Publication Date(Web):2006/12/07
DOI:10.1039/B607030B
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 determined together with the position of extra-framework cations, in a stepwise fashion, progressing from an anhydrous model, via a dielectric continuum model, to finally, a fully atomistic model of the water in the intrazeolite pore space. Our methods reveal the complex interplay of short- and long-range interactions on the optimal structure of such materials.
ZIF-64
Mordenite
Silicic acid (H4O4Si)
Pentoxifylline
Silicate
ZIF-7