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Efficient CO2 photoreduction to CO with >70% product selectivity over a periodic mesoporous organosilica-based heterogeneous catalyst containing molecular cobalt phthalocyanine units.

A versatile and facile strategy based on an inverse electron demand Diels–Alder reaction between 5-norbornen-2-yltriethoxysilane and a tetrazine derivative has been established for the synthesis of a new triethoxysilane precursor containing dipyridylpyridazine units. Such a precursor has been incorporated into the mesostructure of an ethylene-bridged periodic mesoporous organosilica (PMO) material through a one-pot synthesis via a co-condensation method. Upon attachment of Ru- and Ir-complexes to the pendant N-chelating heterocyclic ligands, the resulting decorated PMOs have acted as photosensitizers in artificial photosynthetic systems. The deposition of Pt on these PMOs has allowed us to obtain efficient photocatalytic materials for the hydrogen evolution reaction as a result of electron transfer from the light harvesting Ru- and Ir-complexes to the supported Pt nanoparticles through methyl viologen as an electron relay. They have exhibited total turnover number values of 573 and 846, respectively, under visible light irradiation. The role played by each component and the stability of the photocatalytic systems have been discussed. The present approach paves the way to the synthesis of different materials with coordination sites capable of forming surface complexes to be applied as sensitizers and catalysts.

The presence of potent organic endocrine-disrupting chemicals (EDCs) in natural aquifers can have adverse impacts on public health and the environment. 4-nonylphenol, one such EDC, can be efficiently removed from water by adsorption onto a clayey material. In this work, we created an effective sorbent for this purpose by using co-precipitation and subsequent ion-exchange to intercalate the organic anion deoxycholate into a Mg/Al hydrotalcite. Intercalating deoxycholate ions increased the organophilicity of the hydrotalcite surface. The solid was used to adsorb 4-nonylphenol at different pollutant concentrations and temperatures. The adsorption process was subjected to a kinetic study. Based on the results, the EDC was adsorbed by chemisorption. In addition, based on the equilibrium isotherms used for the process, the Freundlich model was the most accurate in reproducing the adsorption of 4-nonylphenol onto deoxycholate-intercalated hydrotalcite.

This paper presents a novel approach to create bifunctional periodic mesoporous organosilicas containing thiol and sulfonic acid groups (SHm/SO3Hn@PMO) by co-condensation reactions of an own design...

A new heterogeneous catalyst has been synthesized by immobilization of a copper complex on dipyridyl-pyridazine functionalized periodic mesoporous organosilica (dppz-vPMO). This ordered support was first prepared by a co-condensation reaction between vinyltriethoxysilane and 1,2-bis(trimethoxysilyl)ethane and further post-functionalized through a hetero Diels-Alder reaction with 3,6-di-2-pyridyl-1,2,4,5-tetrazine. Techniques such as XRD, N

A biomimetic model complex of the [FeFe]-hydrogenase active site (FeFeOH) with an ethylene bridge and a pendant hydroxyl group has been synthesized, characterized and evaluated as catalyst for the light-driven hydrogen production. The interaction of the hydroxyl group present in the complex with 3-isocyanopropyltriethoxysilane provided a carbamate triethoxysilane bearing a diiron dithiolate complex (NCOFeFe), thus becoming a potentially promising candidate for anchoring on heterogeneous supports. As a proof of concept, the NCOFeFe precursor was anchored by a grafting procedure into a periodic mesoporous organosilica with ethane bridges (EthanePMO@NCOFeFe). Both molecular and heterogenized complexes were tested as catalysts for light-driven hydrogen generation in aqueous solutions. The photocatalytic conditions were optimized for the homogenous complex by varying the reaction time, pH, amount of the catalyst or photosensitizer, photon flux, and the type of light source (light-emitting diode (LED) and Xe lamp). It was shown that the molecular FeFeOH diiron complex achieved a decent turnover number (TON) of 70 after 6 h, while NCOFeFe and EthanePMO@NCOFeFe had slightly lower activities showing TONs of 37 and 5 at 6 h, respectively.

Embargado hasta 15/02/2023 The assembly of atomically dispersed iron–nitrogen (FeN4) sites into graphitic structures is a promising approach for sustainable production of bifunctional electrocatalysts for the oxygen electroreduction (ORR) and oxygen evolution (OER) reactions. In addition, single-atom FeN4 sites at the edges of carbon substrates provide higher electrocatalytic performance than those in plane. Unfortunately, the conventional high-temperature pyrolysis method does not allow the generation of edge-enriched FeN4 single-atom sites. Herein, a novel low-temperature and solvent-free mechanochemical synthesis based on the use of dipyridylpyridazine (dppz) functionalized multilayer graphene as a starting material is proposed for precisely engineered location of these FeN4 active sites at the edges. After careful characterization of these dppz-based materials, the ORR and OER electrocatalytic performance was investigated, demonstrating the efficient formation of FeN4 sites at the edges as well as their excellent bifunctional behavior for the ORR and OER. This work paves the way for the development of sustainable approaches for the generation of edge-enriched FeN4 single atom sites on multilayer graphene structures.

Oleate ion was intercalated into a hydrotalcite obtained using a conventional precipitation method and an alternative, novel method involving microwave-assisted ion exchange. The latter method gave a more crystalline hydrotalcite with better textural properties than the former. The spacing between layers in the hydrotalcites was used to epoxidize the double bond in oleate ion. X-ray diffraction patterns revealed that the layered structure of the hydrotalcites was not altered by the reaction. The epoxidation of oleate ion with m-chloroperbenzoic acid (mCPBA) was monitored using Raman spectroscopy. The results of this work testify to the high potential of hydrotalcites as molecular reactors for reactions in confined spaces.

Different MgAl mixed oxides with a Mg/Al ratio of 2 were obtained through calcination of the corresponding hydrotalcites at 450 °C and tested for MPV reaction of benzaldehyde with 2-butanol. The influence of several synthetic parameters (such as co-precipitation in the presence of Pluronic P123 or homogeneous precipitation in the presence of urea in the medium) on catalytic performance was studied. The use of urea led to a decrease in surface area as compared to conventional precipitation method (125 m2/g and 201 m2/g, respectively) but an increase in surface basicity (7.3 µmol CO2/m2 and 4.3 µmol CO2/m2, respectively). Utilization of Pluronic 123 increases surface area (183 m2/g) though basicity is hardly affected (4.2 µmol CO2/m2). All the catalysts showed a high conversion and high selective to the desired product, observing a relationship between the density of basic sites and the catalytic activity. All in all, the solid exhibiting the highest benzyl alcohol yield was that synthesized in the presence of urea (labelled as HT-U-450), with a rate of 2.05 mmol benzyl alcohol/gcat × min.

This study is devoted to investigate the opportunities of a plasma-catalytic system with CeO2 downstream (i.e. PPC-Post Plasma-catalysis) for the abatement of trichloroethylene (TCE), a typical chlorinated VOC, from dry air. A multi-pin-to-plate negative DC corona/glow discharge is used and showed poor COx selectivity despite having high abatement efficiency due to the formation of oxygenated intermediates such as phosgene, dichloroacetylchloride (DCAC) and trichloroacetaldehyde (TCAA), when operated alone. Nonetheless, NTP enables catalyst activation at lower temperature. As a result, suppression of unwanted chlorinated by-products as well as high COx selectivity at lower energy cost have been achieved, proving that this plasma-catalysis route shows great potential as air pollution control technology for low concentrated VOC air streams. Special attention is given to the effect of catalyst temperature, the role of ozone in the plasma–catalytic TCE abatement and the possible synergy between NTP and catalysis. Also, a long term test to evaluate the stability of CeO2 catalyst has also been successfully performed.

The adsorption of S-metolachlor herbicide from aqueous solution by benzenesilica materials was studied. The materials were synthesized with 1,4-bis(triethoxysilyl)benzene as organosilica precursor and Brij 76 and Pluronic P123 as surfactants. Additionally, 1,3,5-triisopropylbenzene (TPB) was used as porogen to produce microporosity. Those materials obtained by Brij-76 and P123 showed well-structured ordering. However, a disordered microporous benzenesilica material was obtained in presence of P123 and TPB. All materials proved to be efficient adsorbents for S-metolachlor. Among them, the material synthesized with Brij 76 showed the highest adsorption capacity due to its ordered structure and, mainly, to its higher proportion of mesopores.

A global hydrogen economy could ensure environmentally sustainable, safe and cost-efficient renewable energy for the 21st century. Solar hydrogen production through artificial photosynthesis is a key strategy, and the activity of natural hydrogenase metalloenzymes an inspiration for the design of synthetic catalyst systems. [FeFe]-hydrogenase enzymes, present in anaerobic bacteria and green algae, are the most efficient class of biological catalysts for hydrogen evolution. The enzymes operate in an aqueous environment, utilizing electrons that ultimately stem from photosynthesis as the only energy source. Functional synthetic models of the [FeFe]-hydrogenase enzyme active site have garnered intense interest as potential catalysts for the reduction of protons to molecular hydrogen. Herein, we take an extensive journey through the field of biomimetic hydrogenase chemistry for lightdriven hydrogen production. We open with a brief presentation of the structure and redox mechanism of the natural enzyme. Synthetic methodologies, structural characteristics, and hydrogen generation metrics relevant to the synthetic diiron catalysts ([2Fe2S]) are discussed. We first examine multicomponent photocatalysis systems with the [2Fe2S] cluster, followed by photosensitizer-[2Fe2S] dyads and molecular triads. Finally, strategies for the incorporation of [2Fe2S] complexes into supramolecular assemblies, semiconductor supports, and hybrid heterogeneous platforms are laid out. We analyze the individual properties, scope, and limitations of the components present in the photocatalytic reactions. This review illuminates the most useful aspects to rationally design a wide variety of biomimetic catalysts inspired by the diiron subsite of [FeFe]-hydrogenases, and establishes design features shared by the most stable and efficient hydrogen producing photosystems. (C) 2021 The Author(s). Published by Elsevier B.V.

The development of effective, environmentally friendly catalysts for the Baeyer–Villiger reaction is becoming increasingly important in applied catalysis. In this work, we synthesized a 3D composite consisting of silica spheres coated with Mg/Al hydrotalcite with much better textural properties than its 2D counterparts. In fact, the 3D solid outperformed a 2D-layered hydrotalcite as catalyst in the Baeyer–Villiger reaction of cyclic ketones with H2O2/benzonitrile as oxidant. The 3D catalyst provided excellent conversion and selectivity; it was also readily filtered off the reaction mixture. The proposed reaction mechanism, which involves adsorption of the reactants on the hydrotalcite surface, is consistent with the catalytic activity results.

Lithium-sulfur (Li-S) batteries have received enormous interest as a promising energy storage system to compete against limited, non-renewable, energy sources due to their high energy density, sustainability, and low cost. Among the main challenges of this technology, researchers are concentrating on reducing the well-known &ldquo, shuttle effect&rdquo, that generates the loss and corrosion of the active material during cycling. To tackle this issue, metal-organic frameworks (MOF) are considered excellent sulfur host materials to be part of the cathode in Li-S batteries, showing efficient confinement of undesirable polysulfides. In this study, MIL-88A, based on iron fumarate, was synthesised by a simple and fast ultrasonic-assisted probe method. Techniques such as X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), and N2 adsorption/desorption isotherms were used to characterise structural, morphological, and textural properties. The synthesis process led to MIL-88A particles with a central prismatic portion and pyramidal terminal portions, which exhibited a dual micro-mesoporous MOF system. The composite MIL-88A@S was prepared, by a typical melt-diffusion method at 155&deg, C, as a cathodic material for Li-S cells. MIL-88A@S electrodes were tested under several rates, exhibiting stable specific capacity values above 400 mAh g&minus, 1 at 0.1 C (1C = 1675 mA g&minus, 1). This polyhedral and porous MIL-88A was found to be an effective cathode material for long cycling in Li-S cells, retaining a reversible capacity above 300 mAh g&minus, 1 at 0.5 C for more than 1000 cycles, and exhibiting excellent coulombic efficiency.

Desde la inclusión de España en la Declaración de Bolonia, cuyo objetivo es reformar el sistema universitario a través del Espacio Europeo de Educación Superior (EEES), el alumno adquiere un papel de liderazgo en el proceso de enseñanza-aprendizaje. Con el fin de promover la autonomía entre los estudiantes en el proceso de capacitación, el uso de las Tecnologías de la Información y la Comunicación (TIC) es cada vez más común. Entre ellos, el e-learning con aplicaciones móviles tiene un gran potencial para fortalecer el proceso de aprendizaje, dado su uso popular entre los estudiantes universitarios. Esto se debe principalmente a que estas herramientas tienen una variedad de ventajas sobre los métodos tradicionales, como conferencias magistrales, entre los que cabe citar, entre otras, el que permiten la comunicación profesor-estudiante más allá de los espacios tradicionales, rompiendo las barreras o límites de espacio y tiempo, que favorecen la autonomía (autoaprendizaje) del estudiante o que permiten la presentación de la información en una gran variedad de formas y lenguajes. Además, son fácilmente conectables a las redes sociales, lo que hace que el proceso de aprendizaje sea más atractivo, más accesible y más cooperativo. Con el propósito de aumentar la motivación de los estudiantes, en este trabajo, se diseñó y desarrolló una aplicación móvil, en la que se han virtualizado tres laboratorios pertenecientes a la Facultad de Ciencias (Biología y Química) y la Escuela Politécnica Superior (Física de Ingeniería Mecánica) de la Universidad de Córdoba. En cada uno de los tres laboratorios, los estudiantes pueden acceder a información multimedia correspondiente a diversos materiales, equipos, videos, enlaces, laboratorios virtuales, así como una explicación de algunas sesiones prácticas. Para el desarrollo de diferentes escenarios, se han utilizado imágenes panorámicas de 360º, que se han realizado utilizando técnicas HDR (High Dynamic Range). La plataforma elegida para el desarrollo fue Android, debido al uso mayoritario de este sistema operativo en dispositivos móviles entre los estudiantes. Conviene destacar que este tipo de e-learning facilita a los estudiantes el acceso a materiales relacionados con las materias prácticas en estudio que son muy importantes en la enseñanza de las ciencias. Además, se familiarizan más con los términos técnicos de una manera interactiva, más entretenida y eficiente, mejorando el grado de motivación y la participación del estudiante en los temas en estudio. Esto conduce a una mayor asimilación de conocimientos y habilidades. Para verificar esto, para cada laboratorio, dividimos a los estudiantes en un grupo sin acceso a la aplicación (grupo de control) y otro (grupo de prueba) con acceso. Llevamos a cabo una serie de cuestionarios con los grupos de prueba usando la plataforma basada en juegos "Kahoot!" y Google Forms. Los cuestionarios intentaron aclarar el grado de aceptación de la herramienta, el impacto en el aprendizaje de los temas en estudio y la identificación de posibles áreas de mejora. En general, los estudiantes del grupo de prueba encontraron la herramienta muy interesante y les ayudó a mejorar sus puntuaciones en comparación con el grupo de control. No se aprecia una distinción clara entre los estudiantes de diferentes materias. Entre los aspectos a mejorar, se encuentra el contenido relativamente limitado de esta primera versión. Además, la evaluación se realizó con un único grupo control y un grupo de prueba en cada materia, lo que limita su potencial para extraer conclusiones definitivas. En el futuro, se realizarán más cargas y pruebas de contenido en diferentes cursos para evaluar los beneficios del aprendizaje de ciencias mediante esta aplicación. Since the inclusion of Spain in the Bologna Declaration, whose objective is to reform the university system through the European Higher Education Area (EHEA), the student acquires a leading role in the teaching-learning process. In order to promote autonomy among the students in the training process, the use of Information and Communication Technologies (ICT) is increasingly common. Among them, e-learning using mobile apps has a great potential to strengthen the learning process given its popular use among university students. This is mostly because these tools have assorted advantages over traditional methods, e.g. magisterial lectures, such as ubiquitous access, possibility to update and increase content, self-learning, etc. Moreover, they are easily linkable to social media, thus making the learning process more attractive, more easily accessible and more cooperative. For the purpose of increasing student motivation, in this work, a mobile application has been designed and developed, in which three laboratories, belonging to the faculties of Sciences (Biology and Chemistry) and Engineering, have been virtualized. In each of the three laboratories, the students can access to some multimedia information corresponding to various materials and equipment, videos, links, virtual laboratories as well as an explanation of some practical sessions. For the different scenarios development, 360º panoramic pictures have been used, which have been made using HDR (High Dynamic Range) techniques. The platform chosen for the development was Android, due to the majority use of this operating system on mobile devices among the students. It is good to notice that this type of e-learning facilitates students the accessibility to materials related to the practical subjects under study which are very important in science teaching. Furthermore, they become more familiar with technical terms in an interactive, more entertaining and efficient manner, improving the motivation degree and the student's involvement in the subjects under study. This leads to a greater assimilation of knowledge and skills. To verify this, for each laboratory, we divided the students in a group without access to the app (control group) and another one (testing group) with access. We conducted a series of questionnaires with the testing groups using the game-based platform “Kahoot!” and Google Forms. The questionnaires intended to enlighten the degree of acceptance of the tool, the impact on learning of the subjects under study and the identification of potential areas of improvement. Generally, the testing group students found the tool very interesting and helped them improving their scores compared to the control group. No clear distinction between students of different subjects was appreciated. A limited content in this first version was major drawback. Moreover, this evaluation has been conducted only with one control and one testing group of each subject, thus limiting its potential to extract definite conclusions. Further content upload and testing on different courses will be done in the future to evaluate the benefits of science learning using this app.

Silica microspheres obtained by using the Stober method were coated with a 2:1 Mg/Al hydrotalcite to prepare various composites. The composites, labelled SiO2@HT, were characterized by using instrumental techniques including scanning and transmission electron microscopies, and micro-Raman, X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopies. The microspheres were about 0.5 μm in diameter and success in their coating with hydrotalcite was strongly pH-dependent. Thus, a pure SiO2@HT composite could only be obtained by using pH 9, at which the microspheres were coated with horizontally stacked layers of hydrotalcite.

Highly ordered thiol-ethylene bridged Periodic Mesoporous Organosilicas were synthesized directly from a homemade thiol-functionalized bis-silane precursor. These high surface area materials contain up to 4.3 mmol/g sulfur functions in the walls and can adsorb up to 1183 mg/g mercury ions. Raman spectroscopy reveals the existence of thiol and disulfide moieties. These groups have been evaluated by a combination of Raman spectroscopy, Ellman’s reagent and elemental analysis. The adsorption of mercury ions was evidenced by different techniques, including Raman, XPS and porosimetry, which indicate that thiol groups are highly accessible to mercury. Scanning transmission electron microscopy combined with EDX showed an even homogenous distribution of the sulfur atoms throughout the structure, and have revealed for the first time that a fraction of the adsorbed mercury is forming thiolate nanocrystals in the pores. The adsorbent is highly selective for mercury and can be regenerated and reused multiple times, maintaining its structure and functionalities and showing only a marginal loss of adsorption capacity after several runs.

The degradation of methylene blue in aqueous solution as a model dye using a non thermal microwave (2.45 GHz) plasma jet at atmospheric pressure has been investigated. Argon has been used as feed gas and aqueous solutions with different concentrations of the dye were treated using the effluent from plasma jet in a remote exposure. The removal efficiency increased as the dye concentration decreased from 250 to 5 ppm. Methylene blue degrades after different treatment times, depending on the experimental plasma conditions. Thus, kinetic constants up to 0.177 min-1 were obtained. The higher the Ar flow, the faster the degradation rate. Optical emission spectroscopy (OES) was used to gather information about the species present in the gas phase, specifically excited argon atoms. Argon excited species and hydrogen peroxide play an important role in the degradation of the dye. In fact, the conversion of methylene blue was directly related to the density of argon excited species in the gas phase and the concentration of hydrogen peroxide in the aqueous liquid phase. Values of energy yield at 50% dye conversion of 0.296 g/kWh were achieved. Also, the use of two plasma applicators in parallel has been proven to improve energy efficiency.

This work describes the synthesis of thiol-functionalized periodic mesoporous organosilicas (PMOs) prepared using the precursor 1-thiol-1,2-bis(triethoxysilyl)ethane, alone or mixed with 1,2-bis(triethoxysilyl)ethane. The thiol groups incorporated into the structure were found to be efficient for palladium binding. This has allowed these materials to be used as catalysts in the Suzuki cross-coupling reaction of bromobenzene and phenylboronic acid. Their performance has been compared to palladium-supported periodic mesoporous (organo)silicas and important differences have been observed between them. The use of different heterogeneity tests, such as hot filtration test and poisoning experiments, has provided a deep insight into the reaction mechanism and has confirmed that the reaction occurs in the homogeneous phase following a &ldquo, release and catch&rdquo, mechanism. Furthermore, the thiol-functionalized periodic mesoporous organosilica, synthesized using only 1-thiol-1,2-bis(triethoxysilyl)ethane as a precursor, has proven to be an efficient palladium scavenger.

Graphene-based materials exhibit outstanding physical properties and so are potentially applicable in a great variety of fields. Unlike their corresponding oxides, graphite and graphene are not prone to functionalization. Diels-Alder reactions are among the scarce reactions that they can occur without disrupting their conjugated sp(2) systems. Herein, the reaction between graphite and 3,6-di(2pyridyl)- 1,2,4,5-tetrazine under different conditions affords several graphene-based materials consisting of dipyridylpyri-dazine-functionalized few-layer graphene, multilayer graphene and graphite, the sheets of which act as ligands for the grafting of a europium complex. These three materials show strong red emission under 365 nm UV radiation. Their emitting particles can be visualized by confocal microscopy. The rich coordination chemistry of dipyridylpyridazine ligands has potential novel properties for similarly functionalized graphene-based materials grafted with other metal complexes.

Graphene-based materials are highly interesting in virtue of their excellent chemical, physical and mechanical properties that make them extremely useful as privileged materials in different industrial applications. Sonochemical methods allow the production of low-defect graphene materials, which are preferred for certain uses. Graphene nanosheets (GNS) have been prepared by exfoliation of a commercial micrographite (MG) using an ultrasound probe. Both materials were characterized by common techniques such as X-ray diffraction (XRD), Transmission Electronic Microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). All of them revealed the formation of exfoliated graphene nanosheets with similar surface characteristics to the pristine graphite but with a decreased crystallite size and number of layers. An exhaustive study of the particle size distribution was carried out by different analytical techniques such as dynamic light scattering (DLS), nanoparticle tracking analysis (NTA) and asymmetric flow field flow fractionation (AF4). The results provided by these techniques have been compared. NTA and AF4 gave higher resolution than DLS. AF4 has shown to be a precise analytical technique for the separation of GNS of different sizes.

The etherification of glycerol with tert -butyl alcohol has been carried out in the liquid-phase on different sulfonic acid functionalized hybrid silicas obtained by oxidative cleavage of tetrasulfide bridges. These materials exhibited different textural properties and acidities ranging from 0.5 to 2.3 mmol g −1 . First of all, different experimental variables, including the reactant ratio and temperature have been tested and all catalysts were essayed under optimal conditions. The best catalytic behavior of the hybrid silicas was obtained on S 50 TS 50 O (Y h-GTBE = 28%) at 75 °C and autogenous pressure. In fact, the glycerol conversion obtained on S 50 TS 50 O, clearly surpassed that obtained on A-15 (74 and 51%, respectively). The acidity and the hydrophilic character of the sulfonated hybrid silicas solids have been found to be key parameters for their catalytic activity whereas the surface area and porosity do not seem to be advantageous for this reaction. All catalysts were reused and subjected to an extensive characterization.

Layered double hydroxides (LDHs) are natural or synthetic compounds with a layered structure that become mixed oxides of the metals that contain upon calcination at 450–700 °C. The resulting oxides have shown to be excellent solid sorbents for nitrate ions in aqueous solutions. The structure of the original LDH is recovered by rehydration as a result of the so-called “memory effect”. This process, which follows a Lagergren´s pseudo-first order kinetic model, is monitored via the N O stretching vibration band for nitrate ion at 1051 cm–1 in the Raman spectrum. The nitrate uptake is mainly governed by the temperature and the metal ratio in the initial LDH. At higher Mg/Al ratio, the nitrate adsorption rate was lower. Unlike, it was increased with the adsorption temperature with non-linear response, suggesting an endothermic process. The obtained results present Raman spectroscopy a reliable choice for monitoring nitrate uptake, overcoming to many existing alternatives in terms of accuracy and expeditiousness.

Highly crystalline MIL-88A particles have been successfully synthesized via fast ultrasound-assisted processes. The influence of the sonication generator and synthesis time on the structure, crystallinity, morphology and surface area of the materials were studied in detail. Under this modified ultrasonic method, X-ray diffraction patterns of MIL-88A particles showed highly crystalline structures in contrast to those reported in literature. Significant differences on surface areas and microporosity were appreciated under ultrasound conditions employed. Specific surface areas in the range between 179 and 359 m2 g−1 were obtained. That material synthesized under ultrasound batch conditions during 1 h had the highest surface area and microporous character. Different particle sizes and morphologies were obtained depending on the synthesis procedure. In general, probe sonicators led to smaller particle sizes. Moreover, a comparative study of the ethylene adsorption of the MIL-88A particles and several common MOFs in the ethylene adsorption was investigated. The results suggest that the modified ultrasound-assisted procedure for the synthesis of MIL-88A is effective to obtain highly crystalline particles, which are very efficient to adsorb ethylene molecules.

ZSM-5 zeolite samples containing Pt and a second metal (Sn, Cu or Cr) were prepared by different impregnation procedures. All these catalysts were highly active in the transformation of 1-hexene. A great variety of hydrocarbons were obtained, whose proportion depended on the particular catalyst and the reaction conditions. In general, low temperatures (250 °C) favored the double bond shift reaction, whereas medium temperatures (350 °C) predominantly led to cracking and skeletal isomerization. However, cracking was the major reaction at temperatures above 450 °C. The addition of the second metal decreased the hydrogenating activity of Pt and so olefins constituted a considerable fraction in the product. The use of nitrogen as a carrier gas instead of hydrogen favored the formation of both internal and branched olefins while reducing cracking. The reaction products are interesting for their use in gasoline blending.

The synthesis and catalytic activity of a new sulfonic acid-functionalized periodic mesoporous organosilica (PMO) obtained by an in situ oxidation process have been reported. This material was prepared by co-condensation of a homemade thiol-functionalized bis-silane precursor (EtO) 3 Si-R-Si(OEt) 3 (R = CH 2 CHSH) with 1,2-bis(triethoxysilyl)ethane (BTEE) in the presence of a nonionic triblock co-polymer. Thiol groups were oxidized either in situ during the formation of the mesostructure, or by a post-synthesis oxidation of the solid material. The in situ generated sulfonated PMO material had a well-ordered hexagonal mesoporous structure and a narrow pore size distribution. The sulfonic acid concentration of these materials was in the range of 0.85–1.48 mmol H + g −1 . The catalytic performance of these sulfonic acid-functionalized materials was evaluated and compared with the commercial resin Amberlyst-15 in the esterification of acetic acid with benzyl alcohol. The in situ sulfonated PMO has shown to be an efficient, robust, and recyclable catalyst in acid-catalyzed reactions throughout consecutive catalytic cycles.

Three groups of porous non-ordered bridged organosilicas and silicas have been synthesized using three different surfactants of the Tween family as porogens. One group consisted of silica materials while the other two were organosilicas, i.e., ethanesilicas and benzenesilicas, but differing within each group in their textural properties. The adsorption of the herbicide S-metolachlor from an aqueous solution was then compared on all solids. The composition of the walls, i.e., the bridging group, was the main factor governing the adsorption capacity. Broadly, the uptake of the herbicide follows the sequence: benzenesilica > ethanesilica > silica. However, pore volume also has a significant influence on adsorption. Thus, higher capacities result from materials with larger pore volumes and with a larger size of the mesopores. Moreover, surface area and pore size distributions also affect the adsorption behavior, even though their influence seems to be less pronounced. Finally, a comparison between the porous non-ordered (organo)silicas and the corresponding periodic mesoporous (organo)silicas has revealed some interesting features for the use of these materials as adsorbents. Benzenesilicas with a large pore volume and pores in the micropore and/or large mesopore regions seemed to be the best adsorbents for adsorption in a single step whereas periodic mesoporous benzenesilicas were more appropriate for repetitive adsorptions.

In this work we investigate a mesoporous silica (MS) decorated with dipyridyl-pyridazine (dppz) ligands and further grafted with a mixture of Eu

Two materials - a mesoporous silica (MS) and a periodic mesoporous organosilica (PMO) functionalized with dipyridyl-pyridazine (dppz) units were grafted with near-infrared (NIR) emitting lanthanide (Nd3+, Er3+, Yb3+) complexes in an attempt to obtain hybrid NIR emitting materials. The parent materials: dppz-vSilica and dppz-ePMO were prepared by a hetero Diels-Alder reaction between 3,6-di(2-pyridyl)-1,2,4,5- tetrazine (dptz) and the double bonds of either ethenylene-bridged PMO (ePMO) or vinyl-silica (vSilica) and subsequent oxidation. The dppz-vSilica is reported here for the first time. The prepared lanthanide-PMO/silica hybrid materials were studied in depth for their luminescence properties at room temperature and chosen Nd3+ and Yb3+ samples also at low temperature (as low as 10 K). We show that both the dppz-vSilica and dppz-ePMO materials can be used as "platforms" for obtaining porous materials showing NIR luminescence. To obtain NIR emission these materials can be excited either in the UV or Vis region (into the pi -> pi* transitions of the ligands or directly into the f-f transitions of the Ln(3+) ions). More interestingly, when functionalized with Nd3+ or Yb3+ beta-diketonate complexes these materials showed interesting luminescence properties over a wide temperature range (10-360 K). The Yb3+ materials were investigated for their potential use as ratiometric temperature sensors.

A periodic mesoporous organosilica, in particular, a phenylene-bridged material (Ph-PMO), was evaluated for the first time as a sorbent for retaining and eluting fenuron, simazine, atrazine, carbaryl and terbutryn in grape must by solid phase extraction (SPE) prior to their determination with capillary electrophoresis coupled with ultraviolet detection (CE-UV). The analytes were used as model compounds to demonstrate the potential of Ph-PMO for increasing the sensitivity of CE. Under optimal conditions, the limits of detection for the analytes ranged from 0.6 to 4 μg/L, and their limits of quantitation from 2 to 10 μg/L. These values were comparable and, in some cases, even better than those obtained with C18 and HLB materials. Ph-PMO was characterized physicochemically by X-ray diffraction analysis, N2 adsorption–desorption measurements and laser diffraction particle sizing. The sorbent afforded the extraction of atrazine, carbaryl and terbutryn from grape must with mean recoveries ranging from 86 to 105%. Therefore, periodic mesoporous organosilicas possess a high potential as SPE materials.

The ethenylene bridges on the walls of an ethenylene-bridged periodic mesoporous organosilica were successfully modified with a variety of pyrrole derivatives – pyrrole, methylpyrrole, dimethylpyrrole, trimethylpyrrole and 1-phenylpyrrole – through Diels–Alder reactions. X-ray diffraction measurements and N 2 adsorption–desorption analysis confirmed the preservation of the ordering and mesoporosity of the parent material as well as the decoration of the pores with the surface Diels–Alder adducts. Moreover, other techniques such as DRIFT, 13 C and 29 Si nuclear magnetic resonances revealed the formation of the surface N -heterocyclic compounds at the parent ethenylene sites.

A multi-pin-to-plate negative DC corona/glow discharge combined with MnO 2 catalyst placed downstream of the plasma reactor was experimentally investigated for the abatement of trichloroethylene (TCE) in dry air. For the plasma alone system even at 240 J/L, the CO x -selectivity did not exceed 15%, due to the formation of oxygenated intermediates (phosgene, dichloroacetylchloride). However, by combining both systems, the TCE abatement was improved and the selectivity of the process was greatly enhanced towards total oxidation. For the plasma-catalytic system, the activation energy (1.5 kcal/mol) was significantly decreased compared to pure catalytic conditions (8.7 kcal/mol), suggesting that the oxygenated intermediates produced by the plasma are more susceptible for catalytic oxidation than TCE. Furthermore, the ozone produced by the plasma is able to dissociate on the catalyst surface by a Rideal–Eley mechanism, thereby creating peroxide surface groups which greatly improve the oxidation of TCE. Based on the experimental results, a reaction pathway for the plasma-catalytic TCE abatement is suggested.

Two mesoporous materials, i.e., a mesoporous phenolic resin and a mesoporous carbon, were synthesized following a soft template method to test the removal of two pesticides, Bentazon and S-Metolachlor. The adsorbents were characterized by X-ray diffraction analysis, nitrogen adsorption–desorption isotherms, thermogravimetric analysis, transmission electron microscopy, particle size measurement and XPS spectroscopy. Bentazon and S-Metolachlor adsorption kinetics and isotherm studies were carried out at pH 2 and 4, respectively, on these mesoporous materials as well as on a reference commercial carbon. Freundlich, Langmuir, Dubinin–Raduskevich and Temkin models were applied to describe the adsorption behavior with the Langmuir model showing the best fit. The regeneration of the adsorbents was carried out by calcination under nitrogen atmosphere and the results indicated that the regeneration of the mesoporous carbon was more efficient than that of the mesoporous phenolic resin and the commercial carbon after being reused several times. Another disadvantage of commercial carbon was the great loss of material that it experienced after several adsorption–desorption cycles.

A periodic mesoporous organosilica (PMO) functionalized with sulfur units between the organic bridges has been successfully synthesized by a postsynthetic cold vulcanization treatment performed on an ethenylene-bridged PMO material (ethene-PMO). The results of X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and nitrogen adsorption/desorption porosimetry show that the resultant materials have well-ordered hexagonal mesoporous structures with narrow pore size distributions. Moreover, 13C CP/MAS NMR, 29Si MAS NMR, X-ray photoelectron spectroscopy (XPS), and elemental analysis prove the cross-linking between the organic moieties through additional sulfur bridges. Besides the incorporation of a new functionality to this PMO, the vulcanization treatment, reminiscent of that applied to rubber, improves the thermal and hydrothermal stabilities of the material. The vulcanized materials were employed as mercury adsorbents able to be reused without loss of their capacity in repetitive adsorpt...

The synthesis of chiral materials is a great challenge. This work describes the synthesis of Zr-based coordination polymers composed of chiral ligands derived from natural products. L-tartaric acid, dibenzoyl-L-tartaric acid and L-malic acid were selected as ligands from the chiral pool. Their reaction with zirconium oxychloride gave rise to several materials that were characterized by different techniques, such as XRD, Raman spectroscopy, 13C MAS NMR, TGA and N2 adsorption/desorption isotherms. Significant structural and textural properties have been observed depending on the ligand, the synthesis procedure and the metal to ligand ratio. These polymers were used for the first time as catalysts in the cyanosilylation of benzaldehyde with trimethylsilyl cyanide and their activity was compared with that of UiO-66. Different reaction parameters and reusability were studied for this asymmetric reaction. Some of the reported materials were very active in this reaction and provided a remarkable enantioselectivity depending on the reaction conditions.

Various first-row transition metal cations (Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) have been introduced to zeolite beta using ion exchange procedures. Both aluminum and transition metal sites were studied by UV–Vis spectroscopy, XPS and 27Al NMR. Generally, ion exchange favored the incorporation of Al defects into the zeolite framework. The effect of the divalent and trivalent cations on the final zeolite beta structure was found to be considerably different. While divalent cations were mainly exchanged for Bronsted acid sites after calcination, trivalent cations such as Fe3+ were mostly transformed into oxide-like species whilst Cr3+ species were oxidized to Cr6+ species. Their surface properties were quite distinct since only divalent cations generated strong Lewis acid sites, even though the Bronsted acidity decreased in all cases. Their catalytic performance was evaluated in the transformation of methanol to hydrocarbons. Various metal species, i.e., Cr6+, Mn2+, Fe3+ and Zn2+ were found to act as promoters of polymerization or aromatization reactions. In particular, Cr species were found to enhance the catalytic activity in the conversion of methanol and dimethyl ether into higher order hydrocarbons.

Due to their hydrophobic pore systems and high surface areas, periodic mesoporous organosilicas (PMOs) offer unique properties for use as adsorbents of organic compounds. Two organosilicas (ethane-PMO and benzene-PMO) and a silica (PMS) were synthesized following a similar procedure. The adsorption of the herbicide S-Metolachlor from an aqueous solution was then compared on the three solids. Both PMOs exhibited a higher adsorption capacity than their silica counterpart. Additionally, both PMOs showed much higher stability than the PMS, whose mesostructure was seriously damaged under aqueous conditions. Moreover, both PMOs exhibited a very different adsorption behavior. The adsorption of S-Metolachlor on each material was described by different isotherms. The amount retained depended on the pH, and was maximum at pH = 2 for ethane-PMO and at pH = 4 for benzene-PMO. Our results suggest that both hydrophobic and aromatic π–π interactions play an important role in the adsorption of this herbicide. The adsorption capacity of benzene-PMO was very high with a loading of ca. 0.5 g herbicide per gram of adsorbent after successive adsorption cycles.

Three periodic mesoporous materials, i.e., two organosilicas with either ethylene or phenylene bridges and one silica, have been used as supports for Pd nanoparticles. All Pd-supported samples (1.0 wt%) were prepared by the incipient wetness method and subsequently reduced in an H2 stream at 200 °C. Both hydrogen chemisorption and temperature programmed reduction experiments revealed significant differences depending on the support. Pd2+ species were more reducible on the mesoporous organosilicas than on their silica counterpart. Also, remarkable differences on the particle morphology were observed by transmission electron microscopy. All Pd-supported samples were active in the Suzuki cross-coupling reaction between bromobenzene and phenylboronic acid

Hybrid materials with tetrasulfide bridges were synthesised by co-condensation between bis[3-(triethoxysilyl)propyl]tetrasulfide and either tetraethyl orthosilicate or 1,4-bis(triethoxysilyl)benzene under acidic conditions in the presence of Brij-76 as a structure-directing agent. They were post-modified by treatment with H2O2 for 3 h or 24 h. A progressive loss of the mesostructure in the resulting materials was observed upon increasing the S content in the synthesis mixtures. Thus, only those samples with the lowest tetrasulfide content could be considered as periodic mesoporous organosilicas. This effect was even more pronounced upon oxidation. The oxidised materials exhibited a considerable acidity, particularly those with the two precursors in approximately equal amounts. All sulfonic acid functionalised materials were used as catalysts in the esterification of acetic acid with ethanol, and they exhibited a comparable or very similar activity to that of Amberlyst-15. Several mesoporous and microporous hybrid materials were selected and compared to this commercial resin in the transformation of more hydrophobic substrates. Some of these hybrid materials were especially attractive for the transformation of benzyl alcohol and various secondary alcohols.