Two pregnancies of an ornithine carbamoyltransferase defi ciency disease carrier and review of the literature / Dos embarazos de una portadora de la enfermedad por defi ciencia de ornitina transcarbamilasa (OTC) y revisión de la literatura

Background: the underlying cause of the deficiency of ornithine carbamoyltransferase (OTCD) is a gene mutation on the X chromosome. In females, the phenotype is highly variable, ranging from asymptomatic to neurologic compromise secondary to hyperammonemia and it can be prompted by numerous triggers, including pregnancy. Objective: the objective of this article is to report a case of two pregnancies of an OTCD-carrier, and to review the literature describing OTCD and pregnancy, parturition and postpartum. Methods: an extensive search in PubMed in December 2021 was conducted using different search terms. After screening all abstracts, 23 papers that corresponded to our inclusion criteria were identified. Results: the article focuses on the management of OTCD during pregnancy, parturition, and the postpartum period in terms of clinical presentation, ammonia levels and treatment. Conclusions: females with OTCD can certainly plan a pregnancy, but they need a careful management during delivery and particularly during the immediate postpartum period. If possible, a multidisciplinary team of physicians, dietitians, obstetrician-gynecologist, neonatologists, pharmacists, etc. with expertise in this field should participate in the care of women with OTCD and their children during this period and in their adult life.(AU)

Antecedentes: la causa subyacente de la deficiencia de ornitina transcarbamilasa (OTC) es una mutación genética en el cromosoma X. En las mujeres, el fenotipo es muy variable, desde asintomático hasta presentar un compromiso neurológico secundario a hiperamonemia, y puede ser provocado por numerosos factores desencadenantes, incluido el embarazo.Objetivo: el objetivo de este artículo es reportar un caso de dos embarazos de una portadora de OTC, y revisar la literatura que describe OTC y embarazo, parto y posparto. Métodos: se realizó una búsqueda exhaustiva en PubMed en diciembre de 2021 utilizando diferentes términos de búsqueda. Después de examinar todos los resúmenes, identificamos 23 artículos que correspondían a nuestros criterios de inclusión. Resultados: el artículo se centra en el manejo de la OTC durante el embarazo, el parto y el posparto en términos de presentación clínica, niveles de amonio y tratamiento. Conclusiones: las mujeres con OTC pueden planificar un embarazo, pero necesitan un manejo cuidadoso durante el parto, y particularmente, durante el posparto inmediato. Si es posible, un equipo multidisciplinar de médicos, dietistas, ginecólogos-obstetras, neonatólogos, farmacéuticos, etc., con experiencia en este campo, debe participar en el cuidado de las mujeres con OTC y sus hijos durante este periodo y en su vida adulta.(AU)

Interchain-expanded extra-large-pore zeolites.

Stable aluminosilicate zeolites with extra-large pores that are open through rings of more than 12 tetrahedra could be used to process molecules larger than those currently manageable in zeolite materials. However, until very recently1-3, they proved elusive. In analogy to the interlayer expansion of layered zeolite precursors4,5, we report a strategy that yields thermally and hydrothermally stable silicates by expansion of a one-dimensional silicate chain with an intercalated silylating agent that separates and connects the chains. As a result, zeolites with extra-large pores delimited by 20, 16 and 16 Si tetrahedra along the three crystallographic directions are obtained. The as-made interchain-expanded zeolite contains dangling Si-CH3 groups that, by calcination, connect to each other, resulting in a true, fully connected (except possible defects) three-dimensional zeolite framework with a very low density. Additionally, it features triple four-ring units not seen before in any type of zeolite. The silicate expansion-condensation approach we report may be amenable to further extra-large-pore zeolite formation. Ti can be introduced in this zeolite, leading to a catalyst that is active in liquid-phase alkene oxidations involving bulky molecules, which shows promise in the industrially relevant clean production of propylene oxide using cumene hydroperoxide as an oxidant.

Two pregnancies of an ornithine carbamoyltransferase deficiency disease carrier and review of the literature.

Introduction: Background: the underlying cause of the deficiency of ornithine carbamoyltransferase (OTCD) is a gene mutation on the X chromosome. In females, the phenotype is highly variable, ranging from asymptomatic to neurologic compromise secondary to hyperammonemia and it can be prompted by numerous triggers, including pregnancy. Objective: the objective of this article is to report a case of two pregnancies of an OTCD-carrier, and to review the literature describing OTCD and pregnancy, parturition and postpartum. Methods: an extensive search in PubMed in December 2021 was conducted using different search terms. After screening all abstracts, 23 papers that corresponded to our inclusion criteria were identified. Results: the article focuses on the management of OTCD during pregnancy, parturition, and the postpartum period in terms of clinical presentation, ammonia levels and treatment. Conclusions: females with OTCD can certainly plan a pregnancy, but they need a careful management during delivery and particularly during the immediate postpartum period. If possible, a multidisciplinary team of physicians, dietitians, obstetrician-gynecologist, neonatologists, pharmacists, etc. with expertise in this field should participate in the care of women with OTCD and their children during this period and in their adult life.

Introducción: Antecedentes: la causa subyacente de la deficiencia de ornitina transcarbamilasa (OTC) es una mutación genética en el cromosoma X. En las mujeres, el fenotipo es muy variable, desde asintomático hasta presentar un compromiso neurológico secundario a hiperamonemia, y puede ser provocado por numerosos factores desencadenantes, incluido el embarazo. Objetivo: el objetivo de este artículo es reportar un caso de dos embarazos de una portadora de OTC, y revisar la literatura que describe OTC y embarazo, parto y posparto. Métodos: se realizó una búsqueda exhaustiva en PubMed en diciembre de 2021 utilizando diferentes términos de búsqueda. Después de examinar todos los resúmenes, identificamos 23 artículos que correspondían a nuestros criterios de inclusión. Resultados: el artículo se centra en el manejo de la OTC durante el embarazo, el parto y el posparto en términos de presentación clínica, niveles de amonio y tratamiento. Conclusiones: las mujeres con OTC pueden planificar un embarazo, pero necesitan un manejo cuidadoso durante el parto, y particularmente, durante el posparto inmediato. Si es posible, un equipo multidisciplinar de médicos, dietistas, ginecólogos-obstetras, neonatólogos, farmacéuticos, etc., con experiencia en este campo, debe participar en el cuidado de las mujeres con OTC y sus hijos durante este periodo y en su vida adulta.

2-Isopropyl-1,3-dimethylimidazolium as a versatile structure-directing agent in the synthesis of zeolites.

An organic cation lacking specificity in its structure-directing action offers the possibility, through the screening of other structure-directing parameters, to synthesize a variety of zeolites. In this work we show that the organic structure-directing agent 2-isopropyl-1,3-dimethylimidazolium (2iPr13DMI) can produce up to seven different zeolite phases depending on water concentration, the presence of inorganic impurities, crystallization temperature and time, and germanium molar fraction. The obtained phases are very different in terms of pore system, connectivity of the zeolite structure and structural units. At the pure SiO2 side, ZSM-12 and SSZ-35 dominate, with ZSM-12 being favored by the presence of potassium impurities and by less concentrated conditions. The introduction of Ge at low levels favors SSZ-35 over ZSM-12 and as the Ge fraction increases it successively affords CSV, -CLO and two distinct UOS zeolites, HPM-11 and HPM-6. These two zeolites have the same topology but distinct chemical compositions and display powder X-ray diffraction patterns that are much different from each other and from that of as-synthesized IM-16 (UOS reference material). They also show different symmetry at 96 K. Rietveld refinements of the three as-made UOS materials mentioned are provided. HPM-6 and HPM-11 are produced in distinct, non-adjacent crystallization fields. The frequent cocrystallization of the chiral STW zeolite, however, did not afford its synthesis as a pure phase. Molecular mechanics simulations of the location of the organic cation and host-guest interactions fail to explain the observed trends, but also considering the intrinsic stability of the zeolites and the effect of germanium help to rationalize the results. The study is completed by DFT calculations of the NMR chemical shifts of 13C in UOS (helping to understand splittings in the spectrum) and 19F in CSV (supporting the location of fluoride inside the new [4452], which is an incomplete double 4-ring).

Implementation of a parenteral nutrition home care programme in a tertiary hospital / Implementación de un programa de atención domiciliaria de nutrición parenteral en un hospital de tercer nivel

Aim: the objective of this study was to describe the results of the implementation of a home parenteral nutrition (HPN) care programme (Nutrihome©) in a cohort of patients treated at a tertiary hospital. Methods: retrospective study of the patients included in Nutrihome© at Hospital General Universitario Gregorio Marañón, Madrid, Spain. Nutrihome consists of different modules including pre-discharge nursing hospital visits and nursing home visits, deliveries of the infusion pump, consumables and parenteral nutrition bags, patient training, weekly scheduled nursing home visits, scheduled nursing phone calls, stock control phone calls and 24-hour on-call line manned by the nurses. Results: the study included 8 (75 % women) and 10 (70 % women) patients in the Nutrihome© pilot and Nutrihome© programme, respectively. A total 37 adverse events were reported during Nutrihome© pilot, 26 of which were technical, 9 clinical, 1 was catheter-related and 1 other event. Nutrihome© programme registered a total of 107 adverse events reported, 57 of which were technical, 21 clinical, 16 were catheter-related and 13 were other events. A total of 99 % of these events were solved by Nutrihome© via phone calls or home visits. Conclusions: Nutrihome© programme has been extremely useful during this pandemic, facilitaing both the start of HPN and training at the patient home without the need for hospitalisation. Additionally, the adverse events reported and solved by Nutrihome© not only reduced the physicians’ burden during those tough times and the patients´ stress of being hospitalised during a pandemic, but supported the entire healthcare system. (AU)

Objetivo: el objetivo de este estudio fue describir los resultados de la implementación de un programa de cuidados de nutrición parenteral domiciliaria (NPD) (Nutrihome©) en una cohorte de pacientes atendidos en un hospital terciario. Métodos: estudio retrospectivo de los pacientes incluidos en Nutrihome© en el Hospital General Universitario Gregorio Marañón de Madrid (España). Nutrihome consta de diferentes módulos que incluyen visitas de enfermería previas al alta y visitas al domicilio, entregas de la bomba de infusión, consumibles y bolsas de nutrición parenteral, formación del paciente, visitas semanales al domicilio programadas, llamadas telefónicas de enfermería programadas, llamadas telefónicas de control de existencias y atención telefónica de enfermería las 24 horas al día. Resultados: el estudio incluyó a 8 (75 % mujeres) y 10 (70 % mujeres) pacientes en el piloto Nutrihome© y en el programa Nutrihome©, respectivamente. Durante el piloto, se registraron un total de 37 eventos adversos, de los cuales 26 fueron técnicos, 9 clínicos, 1 relacionado con el catéter y 1 otro evento. Durante el programa Nutrihome©, se registró un total de 107 eventos adversos, de los cuales 57 fueron técnicos, 21 clínicos, 16 relacionados con el catéter y 13 otros eventos. El 99 % de estos eventos fueron resueltos por Nutrihome© por teléfono o mediante visitas a domicilio. Conclusiones: el programa Nutrihome© ha sido de gran utilidad durante esta pandemia, posibilitando tanto el inicio de la NPD como la formación en el domicilio del paciente sin necesidad de hospitalización. Además, los eventos adversos descritos y resueltos por Nutrihome© no solo redujeron la carga de los médicos durante esos tiempos difíciles y el estrés de los pacientes derivado de estar hospitalizados durante la pandemia, sino que fue un apoyo para todo el sistema de salud. (AU)

Implementation of a parenteral nutrition home care programme in a tertiary hospital.

Introduction: Aim: the objective of this study was to describe the results of the implementation of a home parenteral nutrition (HPN) care programme (Nutrihome©) in a cohort of patients treated at a tertiary hospital. Methods: retrospective study of the patients included in Nutrihome© at Hospital General Universitario Gregorio Marañón, Madrid, Spain. Nutrihome consists of different modules including pre-discharge nursing hospital visits and nursing home visits, deliveries of the infusion pump, consumables and parenteral nutrition bags, patient training, weekly scheduled nursing home visits, scheduled nursing phone calls, stock control phone calls and 24-hour on-call line manned by the nurses. Results: the study included 8 (75 % women) and 10 (70 % women) patients in the Nutrihome© pilot and Nutrihome© programme, respectively. A total 37 adverse events were reported during Nutrihome© pilot, 26 of which were technical, 9 clinical, 1 was catheter-related and 1 other event. Nutrihome© programme registered a total of 107 adverse events reported, 57 of which were technical, 21 clinical, 16 were catheter-related and 13 were other events. A total of 99 % of these events were solved by Nutrihome© via phone calls or home visits. Conclusions: Nutrihome© programme has been extremely useful during this pandemic, facilitaing both the start of HPN and training at the patient home without the need for hospitalisation. Additionally, the adverse events reported and solved by Nutrihome© not only reduced the physicians' burden during those tough times and the patients´ stress of being hospitalised during a pandemic, but supported the entire healthcare system.

Introducción: Objetivo: el objetivo de este estudio fue describir los resultados de la implementación de un programa de cuidados de nutrición parenteral domiciliaria (NPD) (Nutrihome©) en una cohorte de pacientes atendidos en un hospital terciario. Métodos: estudio retrospectivo de los pacientes incluidos en Nutrihome© en el Hospital General Universitario Gregorio Marañón de Madrid (España). Nutrihome consta de diferentes módulos que incluyen visitas de enfermería previas al alta y visitas al domicilio, entregas de la bomba de infusión, consumibles y bolsas de nutrición parenteral, formación del paciente, visitas semanales al domicilio programadas, llamadas telefónicas de enfermería programadas, llamadas telefónicas de control de existencias y atención telefónica de enfermería las 24 horas al día. Resultados: el estudio incluyó a 8 (75 % mujeres) y 10 (70 % mujeres) pacientes en el piloto Nutrihome© y en el programa Nutrihome©, respectivamente. Durante el piloto, se registraron un total de 37 eventos adversos, de los cuales 26 fueron técnicos, 9 clínicos, 1 relacionado con el catéter y 1 otro evento. Durante el programa Nutrihome©, se registró un total de 107 eventos adversos, de los cuales 57 fueron técnicos, 21 clínicos, 16 relacionados con el catéter y 13 otros eventos. El 99 % de estos eventos fueron resueltos por Nutrihome© por teléfono o mediante visitas a domicilio. Conclusiones: el programa Nutrihome© ha sido de gran utilidad durante esta pandemia, posibilitando tanto el inicio de la NPD como la formación en el domicilio del paciente sin necesidad de hospitalización. Además, los eventos adversos descritos y resueltos por Nutrihome© no solo redujeron la carga de los médicos durante esos tiempos difíciles y el estrés de los pacientes derivado de estar hospitalizados durante la pandemia, sino que fue un apoyo para todo el sistema de salud.

A 3D extra-large-pore zeolite enabled by 1D-to-3D topotactic condensation of a chain silicate.

Zeolites are microporous silicates with a large variety of applications as catalysts, adsorbents, and cation exchangers. Stable silica-based zeolites with increased porosity are in demand to allow adsorption and processing of large molecules but challenge our synthetic ability. We report a new, highly stable pure silica zeolite called ZEO-3, which has a multidimensional, interconnected system of extra-large pores open through windows made by 16 and 14 silicate tetrahedra, the least dense polymorph of silica known so far. This zeolite was formed by an unprecedented one-dimensional to three-dimensional (1D-to-3D) topotactic condensation of a chain silicate. With a specific surface area of more than 1000 square meters per gram, ZEO-3 showed a high performance for volatile organic compound abatement and recovery compared with other zeolites and metal-organic frameworks.

Diets for inflammatory bowel disease: What do we know so far?

In recent years, the role of diet in the pathogenesis of inflammatory bowel disease (IBD) has gained great interest within the scientific community. Eating habits from industrialised countries (the so-called western diet or WD) have been associated with a higher incidence of IBD in observational studies, although the dietary factors responsible for the development of the disease are still to be elucidated. Some components of the diet with proinflammatory potential may cause changes in immunity and intestinal microbiota, leading to the inflammatory reaction that causes IBD-related lesions. The quality of available evidence is low, due to methodological issues, such as the lack of intervention studies, small sample size and heterogeneity of studies. For this reason, scientific societies have offered their recommendations using clinical practice guidelines and consensus documents, in order to establish a common criterion in the nutritional treatment of patients with IBD. The objective of this review was to summarise the data published regarding diet in IBD and review the recommendations given by scientific societies.

A stable aluminosilicate zeolite with intersecting three-dimensional extra-large pores.

Zeolites are crystalline porous materials with important industrial applications, including uses in catalytic and adsorption-separation processes. Access into and out of their inner confined space, where adsorption and reactions occur, is limited by their pore apertures. Stable multidimensional zeolites with larger pores able to process larger molecules are in demand in the fine chemical industry and for the oil processing on which the world still relies for fuels. Currently known extra-large-pore zeolites display poor stability and/or lack pore multidimensionality, limiting their usefulness. We report ZEO-1, a robust, fully connected aluminosilicate zeolite with mutually intersecting three-dimensional extra-large plus three-dimensional large pores. ZEO-1 is stable up to 1000°C, has an extraordinary specific surface area (1000 square meters per gram), and shows potential as a catalytic cracking catalyst.

Synthesis of Extra-Large Pore, Large Pore and Medium Pore Zeolites Using a Small Imidazolium Cation as the Organic Structure-Directing Agent.

One common strategy in the search for new zeolites is the use of organic structure-directing agents (OSDA). Typically, one seeks to achieve a high specificity in the structure-directing effect of the OSDA. This study shows, however, that an OSDA lacking strong specificity towards any particular zeolite may provide opportunities for discovery when other synthesis parameters are systematically screened. Thus, 1-methyl-2-ethyl-3-n-propylimidazolium has allowed to crystallize the new large/medium pore zeolite HPM-16 as well as the recently reported extra-large pore -SYT and the medium/small pore and chiral STW. The sophisticated OSDA originally affording -SYT and the new simple OSDA have very little in common, both in terms of size, shape and flexibility, while both may still direct the synthesis of the same zeolite. In fact, molecular simulations show that the new OSDA is located in three different positions of the -SYT structure, including the discrete 8MR where the original organic could not fit.

HPM-16, a Stable Interrupted Zeolite with a Multidimensional Mixed Medium-Large Pore System Containing Supercages.

HPM-16 is a highly porous germanosilicate zeolite with an interrupted framework that contains a three-dimensional system of 12+10×10(12)×12+10-membered ring (MR) pores. The 10(12) MR pore in the b direction is a 10 MR pore with long 12 MR stretches forming 30 Šlong tubular supercages. Along one direction the 10 MR pores are fused, meaning that the separation between adjacent pores consists of a single tetrahedron that is, additionally, connected to only three additional tetrahedra (a Q3 ). These fused pores are thus decorated by T-OH groups along the whole diffusion path, creating a hydrophilic region embedded in an otherwise essentially hydrophobic environment. The structure is built from highly porous 12×12×12 MR uninterrupted layers that are connected to each other through Q3 producing a second system of 10×10×10 MR pores. This zeolite can be extensively degermanated yielding a material with high thermal stability, despite its interrupted nature.

Structure-direction towards the new large pore zeolite NUD-3.

The new zeolite NUD-3 possesses a three-dimensional system of large pore channels that is topologically identical to those of ITQ-21 and PKU-14. However, the three zeolites have distinctly different frameworks: a particular single 4-membered ring inside the denser portion of the zeolite is missing in PKU-14, disordered in ITQ-21 and fully ordered in NUD-3. We document these differences and use molecular simulations to unravel the mechanism by which a particular structure directing agent dication, 1,1'-(1,2-phenylenebis(methylene))bis(3-methylimidazolium), is able to orient this inner ring.

HPM-14: A New Germanosilicate Zeolite with Interconnected Extra-Large Pores Plus Odd-Membered and Small Pores*.

HPM-14 is a new extra-large pore zeolite synthesized using imidazolium-based organic structure-directing agents (SDAs), fluoride anions, and germanium and silicon as tetrahedral components of the framework. Owing to the presence of stacking disorder, the structure elucidation of HPM-14 was challenging, and different techniques were necessary to clarify the details of the structure and to understand the nature of the disorder. The structure has been solved by three-dimensional electron-diffraction technique (3D ED) and consists of an intergrowth of two polymorphs possessing a three-dimensional channel system, including an extra-large pore opened through windows made up of sixteen tetrahedral atoms (16-membered ring, 16MR) as well as two additional sets of odd-membered (9MR) and small (8MR) pores. The intergrowth has been studied by scanning transmission electron microscopy (Cs -STEM) and powder X-ray diffraction simulations (DIFFaX), which show a large predominance of the monoclinic polymorph A.

Social and economic costs of home parenteral nutrition.

BACKGROUND AND AIMS: Home parenteral nutrition (HPN) is a lifesaving treatment for people with chronic intestinal failure. Although HPN has been studied from an economic point of view, the categories of costs usually included direct costs, frequently excluding personal costs and productivity costs. The purpose of the present paper was to study the total costs of HPN from a societal perspective. METHODS: Observational, retrospective, transverse study of all adult patients who were on HPN for more than 3 months and were treated at Gregorio Marañón University Hospital (Madrid, Spain), from June 2018-2019. Data on personal costs and productivity costs were collected from questionnaires completed by patients receiving HPN. We also updated the direct healthcare and non-healthcare costs studied by our group previously to Euros (€) for the year 2019. RESULTS: Twenty-two patients were included. Personal costs were €729.49 per patient (€3.45 per patient per day) and productivity costs were €256.39 per patient (€1.21 per patient per day). Total HPN costs amounted to €14,460.87 per patient (€131.58 per patient per day). The direct healthcare and non-healthcare costs accounted for 96.46% of overall costs, the personal costs for the patients receiving HPN accounted for 2.62% and productivity costs for 0.92%. CONCLUSIONS: From a societal perspective, the direct healthcare and non-healthcare costs accounted for the majority of HPN expenditure, followed by personal costs and productivity costs.

Structural characterization of HPM-7, a more ordered than expected germanosilicate zeolite.

HPM-7, a germanosilicate synthesized using long imidazolium-based dications with two different linkers, is shown to possess the POS topology, although disorder may exist but it is very difficult to discern. First, three simple ordered polymorphs (POS-A to POS-C) with very similar energies and structural motifs could give rise to intergrowths that would be very difficult to recognize by powder X-ray diffraction, according to DIFFaX simulations. Another four structures (POS-D to POS-G) can be derived from POS by changing the orientation of two single four rings within the structure, possibly providing an additional source of disorder. While 3D EDT strongly suggests that HPM-7 basically possesses the POS-A (i.e. POS) topology, a detailed HR-STEM study demonstrates the rare existence of some disorder compatible with the polymorph POS-D. The general avoidance of polymorphs with very similar structural motifs and comparable energies points to a rather specific structure-direction by the organic dications used.

IDM-1: A Zeolite with Intersecting Medium and Extra-Large Pores Built as an Expansion of Zeolite MFI.

IDM-1 is a new silica zeolite with an ordered and well-defined framework constructed by alternating pentasil layers and interrupted layers, giving rise to an intersecting system of straight medium pores and undulating extra-large lobed pores. This unique structure was solved by rotation electron diffraction and refined against synchrotron powder X-ray diffraction data. Despite the presence of both Si(OSi)3 (OH) and Si(OSi)2 (OH)2 sites, this new zeolite presents high thermal stability, withstanding calcination even to 1000 °C. The location of defects at specific sites of the structure results in alternating hydrophobic SiO2 and hydrophilic SiO(2-x) (OH)2x intracrystalline regions. This peculiar combination of intersecting medium and extra-large pores and alternating regions of different chemical character may provide this zeolite with unique catalytic properties.

Synthesis of a germanosilicate zeolite HPM-12 using a short imidazolium-based dication: structure-direction by charge-to-charge distance matching.

A short imidazolium based dication, with only three methylene units in the spacer linker, selectively directs the crystallization of zeolite HPM-12 (*UOE) as long as there is enough germanium present in the synthesis gel. The integrity of the dication is proved by dissolution of the zeolite and 1H and 13C NMR spectroscopy, where significant effects of organic dication concentration and the presence and concentration of HF need to be taken into account. For the as-made HPM-12 zeolite, a large shift of 9 ppm of one resonance in the 13C MAS NMR spectrum is due to the particular conformation of the dication imposed by confinement in the zeolite framework, as found by DFT calculations. The structure-directing ability of this kind of dication with varying length of the linker suggests that matching of the distance between positive charges (imidazolium moieties) and negative charges (double four rings in which fluoride resides) plays a crucial role during crystallization.

Synthesis of Pure Silica MWW Zeolite in Fluoride Medium by Using an Imidazolium-Based Long Dication.

As the spacer length in 1,2-dimethylimidazolium-based dications increases beyond a specific point (six methylene units), they fail in structure-directing towards STW zeolites in any synthetic conditions. These dications can instead produce, under fluoride concentrated conditions, either *BEA [in the case of the eight-methylene-unit structure-directing agent (SDA)] or MWW (ten methylene units) zeolites. For any length of the dication, the default zeolite (MTW) is a relatively dense zeolite containing a unidimensional channel, whereas the zeolite demanding most specificity (STW, *BEA or MWW) is more porous, affording a larger concentration of the dication to be occluded. This work provides the first reported fluoride synthesis of pure silica MWW zeolites. Charge balance of the organic dications in this zeolite was achieved by combining "structural" silanolates, regular "connectivity defects" and occluded fluoride. Molecular mechanics calculations showed a perfect fit of the decamethylenebis(dimethylimidazolium) dication in the sinusoidal intralayer pore system of MWW. The calculations showed also that the dication is able to stabilize the interlayer space without disturbing the hydrogen-bonding system that holds the layers together in the as-made material. The 19 F magic-angle spinning (MAS) NMR presented two distinct resonances at -71 and -83 ppm, which, on the basis of DFT calculations, we tentatively assigned to fluoride occluded in [46 62 ] and [41 52 62 ] cages of the MWW structure, respectively. The same DFT study determines a different chemical shift of one methyl 13 C nuclear magnetic resonance according to the imidazolium ring residing in the sinusoidal channels or in the large cup cavities, thus explaining an experimentally observed splitting of that resonance.

Synthesis of pure silica MFI zeolites using imidazolium-based long dications. A comparative study of structure-directing effects derived from a further spacer length increase.

Length-dependent structure direction of linear methylimidazolium-based dications towards MFI zeolite, previously known only for the tetramethylene spacer, has also been found for octamethylene and decamethylene spacers. This works only under highly concentrated conditions, whereas dilution always tends to favor TON, a default structure that is the only zeolite obtained with the other reported dications (with tri-, penta-, and hexamethylene spacers). The locations and conformations of the dications have been studied by molecular mechanics simulations. As longer dications introduce lower density of positive charges in the zeolite, the density of connectivity defects also decreases. Finally, these long dications cannot easily place each charged imidazolium ring in the two possible orientations (either parallel or perpendicular to 4MR close to F- sites) found for the tetramethylene case. Hence, although the three MFI materials display two 19F NMR resonances at similar chemical shifts, their relative intensities strongly vary as a function of the spacer length.

Stepped Propane Adsorption in Pure-Silica ITW Zeolite.

Gas adsorption over zeolites is at the basis of important applications of this class of microporous crystalline solids, notably as separation media and catalysts, but it may also be complex and not straightforward to understand. Here we report that for temperature below 323 K propane adsorption on the small-pore pure-silica zeolite ITW exhibits a clear step (pseudosaturation). This is absent in the case of propene and the other small linear alkanes. An intermediate plateau, clearly observed in the 293 K isotherm, always occurs when one molecule of propane is loaded in every other cage, i.e., at half-saturation. The simulation results show a swelling of the ITW structure upon propane adsorption. The strong dependence of available pore volume on the adsorbate loading level implies that adsorption cannot occur on the void structure while saturation can only be reached on highly loaded structures. To account for this unprecedented adsorption phenomenon, we propose the term "guest-modulated effect".