CuAl2O4 based mixed oxides were used as heterogeneous catalysts for ozone activation to degrade organics in aqueous solution. The solids were thoroughly characterized by SEM/EDS, N2 physisorption, ...XRD, FTIR, Pyridine-FTIR, TEM and XPS. We demonstrated that the solid precursor calcined at 300 °C exhibited the best catalytic ozonation activity with respect to CuAl2O4 spinel phase obtained at higher temperatures. Such performance was attributed to the better textural properties and a higher density of active sites (hydroxyl groups and Lewis acidity). Specifically, the mixed oxide/O3 process allows to reach a near complete color removal of the dye solution (100 mg L−1) in 25 min at neutral pH. Corresponding reaction rate value was measured at 0.112 min−1 and was clearly higher compared with the single oxide ozonation process (0.071 min−1 for CuO/O3 and 0.074 min−1 for Al2O3/O3). Then, we proposed that such catalytic performance was related to a synergistic function between ≡Cu2+ and ≡Al3+, which took part of a mechanism of radical formation. In such mechanism, present ≡Al3+ could act as a reservoir for surface active sites such as hydroxyl groups and Lewis acid sites, while ≡Cu2+ could provide the possibility of electron transfer with ozone for the enhancement of radical generation. We suggested that the interaction between chemisorbed ozone and surface hydroxyl groups initially stabilized on ≡Al3+ initiated the generation of reactive radical species. This interaction led as well to the formation of surface adsorbed HO and few O2− on ≡Cu2+ Lewis acid sites. Besides, the interfacial redox reaction with ozone is favored by the presence of ≡Cu2+ following the sequence of ≡Cu2+/≡Cu+/≡Cu2+ redox cycle.
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•The precursor has a better catalytic activity than CuAl2O4 with spinel phase.•Kinetic of catalytic ozonation over spinel was fully evaluated.•Cu2+ sites allow electron transfer with ozone for radicals generation.•A synergistic function between ≡Cu2+ and ≡Al3+ was illuminated in details.•Surface adsorbed HO and O2− were responsible for the organics degradation.
In order to use MOFs in virus decontamination processes, four archetypal MOFs with different metal clusters have been chosen: UiO-66 (Zr), HKUST-1 (Cu), MIL-53 (Fe) and MIL-125 (Ti). Five different ...concentrations (from 0.01 to 1 mg/mL) for each MOF and three different cell lines (Huh7 TMPRSS2, VeroE6 and Vero81.6) were investigated in aqueous medium (DMEM). Moreover, different cytotoxicity assays were evaluated (MTS, Neutral Red and LDH) and critically compared for the first time, with Neutral Red seemingly to be the most appropriate. HKUST-1 was found to be toxic above 0.1 mg/mL for all of the three cell lines, while the other three MOFs appear to be nontoxic, even above 1 mg/mL. Then, their effect against viruses was monitored, mainly for HCoV-229E and SARS-CoV-2, two different coronaviruses that still cause a lot of infection cases and deaths up to now. Following 1 hour contact with the viruses, HKUST-1 (Cu) and MIL-125 (Ti) were able to greatly diminish the viral titer by 86% and 79.2%, respectively, for HCoV-229E, whereas for SARS-CoV-2 HKUST-1 (Cu), MIL-53 (Fe) and UiO-66 (Zr), demonstrated an efficacy of 68.4%, 63.1% and 56.1%, respectively.
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•Reliable protocol to determine the effectiveness of MOFs as antiviral agents.•MOFs for the decontamination of coronaviruses, including mortal SARS-CoV-2.•Deep analysis of the cytotoxicity of some MOFs.
We report the first catalytic application of pore-expanded KIT-6 propylsulfonic acid (PrSO3H) silicas, in fatty acid esterification with methanol under mild conditions. As-synthesized PrSO3H-KIT-6 ...exhibits a 40 and 70% enhancement in turnover frequency (TOF) toward propanoic and hexanoic acid esterification, respectively, over a PrSO3H-SBA-15 analogue of similar 5 nm pore diameter, reflecting the improved mesopore interconnectivity of KIT-6 over SBA-15. However, pore accessibility becomes rate-limiting in the esterification of longer chain lauric and palmitic acids over both solid acid catalysts. This problem can be overcome via hydrothermal aging protocols which permit expansion of the KIT-6 mesopore to 7 nm, thereby doubling the TOF for lauric and palmitic acid esterification over that achievable with PrSO3H-SBA-15.
Metal-organic frameworks represent a class of porous materials which have developed considerably over the past few years. Their highly porous structure makes them outperform conventional adsorbents ...in hot topics such as dihydrogen and methane storage, and carbon dioxide capture. Their consequent modularity, based on the assembly of organic linkers and metal ions or clusters, also brings novel perspectives in catalysis, sensing and drug delivery just to name a few. However, one of the main bottlenecks to their broader use remains their shaping. Especially, shaped materials should present long-term mechanical stability as well as preserve their physical and chemical properties. This makes shaping of MOFs a special case as their thermal and chemical stabilities remain a downside as compared to other traditional porous materials such as silicas and zeolites today. Therefore, ever-increasing efforts have been devoted to the shaping of these materials. In this review, the state of the art for the preparation of shaped 3D MOF-based materials will be presented. Emphasis will be given to the final physical and chemical properties of the shaped solids comparatively to the initial powders, when data are available. In the first part, traditional techniques based on applying a significant force to MOF-based powders will be reviewed. These include pelletization, granulation, and extrusion, which generally lead to an increase of the final volumetric gas uptake of the objects. At the same time, the advantages and disadvantages of each technique will be discussed as well as the main outcome on the final objects. In the second part, the focus will be on newly-emerging techniques such as 3D printing and spray drying. The former also maximizes the volumetric gas uptake of the final materials, and for both techniques the quality of the final objects heavily relies on the working parameters. Finally, the third part will include the so-called "phase separation" shaping techniques which are for the most part performed without using special techniques. This implies shaping
via
physical and chemical phenomena such as sublimation and precipitation. Subsequently, a discussion on the performance of these materials for adsorption-based applications will be provided. Finally, perspectives and future outlook will be discussed.
This review discusses the impact of shaping techniques on the physico-chemical properties of metal-organic frameworks.
Modulating the interaction between Mo nanoparticles and their support is an elegant approach to finely tune the structural, physico-chemical, redox and electronic properties of the active site. In ...this work, a series of molybdenum nitride catalysts supported on TiO
2
, and SBA-15 has been prepared and fully characterized. The results of characterization confirmed the high dispersion of Mo and the formation of small molybdenum nanoparticles in both the 10-Mo-N/SBA-15 and 10-Mo-N/TiO
2
catalysts. In this context, we have shown that the catalytic activity of Mo species was strongly impacted by the nature of the catalytic support. Amongst the studied supports, SBA-15 was found to be the most appropriate for Mo dispersion. In comparison, when supported on a reducible oxide (TiO
2
), Mo species showed poor catalytic activity in both ammonia synthesis and decomposition and were prone to quick deactivation in the ammonia synthesis reaction. Evidence of charge transfer from the reducible support to the active phase, indicative of possible SMSI behaviour, has been observed by XPS and EPR. Differences in the oxidation states, redox behaviours, and electronic properties have been further studied by means of EPR, H
2
-TPR and H
2
-TPD.
An elegant approach to finely tune the structural, physico-chemical, redox and electronic properties of the active site by modulating the interaction between Mo nanoparticles and their support.
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•A mineral acid etching process was developed to obtain LaMnO3/MnOx catalysts.•Pseudomorphic transformation of the LaMnO3 precursor toward ε-MnO2 is first proposed.•High surface area ...and hierarchical macro/meso-porous ε-MnO2 materials were obtained.•Good stability of hierarchical ε-MnO2 was achieved with H2O (T50 = 99 °C).
A simple template-free method, based on a mineral acid etching process using manganite perovskite (LaMnO3) as precursor, was successfully developed to obtain a series of 3D meso/macro-porous materials. The LaMnO3 transformation was fully investigated using ICP, XRD, N2 physisorption, TPR, TPD, SEM, TEM/EDS and XPS. This transformation proceeds through a soft-chemical process involving the dissolution of trivalent lanthanum and manganese from the perovskite structure and the dismutation of Mn3+ cations into MnO2 and Mn2+ species. Strength and oxidizing properties of the acid used as modifying agent strongly impact textural and redox surface properties of the resulting materials. Specifically, extending the acid etching duration promotes the surface area and pore volume of the materials while developing interconnected macro-mesoporous networks. In our case, this soft process allowed us to obtain the ε-MnO2 phase with hierarchical porosity without any template. Superior catalytic properties of ε-MnO2 were observed toward HCHO oxidation as well as a good catalytic stability with respect to other macro-mesoporous counterparts. In the light of the experimental results, such performances can be related to the formation of a meso/macro-porous structure conferring high surface area and good accessibility of the active surface sites. The latter exhibit greater redox ability of the manganese species and a higher density of active surface oxygen species with respect to the perovskite precursor.
Using the Milling-Assisted Loading (MAL) solid-state method for loading a poorly water-soluble drug (ibuprofen, IBP) within the SBA-15 matrix has given the opportunity to manipulate the physical ...state of drugs for optimizing bioavailability. The MAL method makes it easy to control and analyze the influence of the degree of loading on the physical state of IBP inside the SBA-15 matrix with an average pore diameter of 9.4 nm. It was found that the density of IBP molecules in an average pore size has a direct influence on both the glass transition and the mechanism of crystallization. Detailed analyzes of the crystallite distribution and melting by Raman mapping, x-ray diffraction, and differential scanning calorimetry have shown that the crystals are localized in the core of the channel and surrounded by a liquid monolayer. The results of these complementary investigations have been used for determining the relevant parameters (related to the SBA-15 matrix and to the IBP molecule) and the nature of the physical state of the confined matter.
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