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The combination between photoactive molecules and inorganic structures is of great interest for the development of advanced materials in the field of optics. Particularly, zeotypes with extra-large pore size are attractive because they allow the encapsulation of bulky dyes. The microporous aluminophoshate Mg-ITQ-51 (IFO-type structure) represents an ideal candidate because of the synergic combination of two crucial features: the IFO framework itself, which is composed of non-interconnected one-dimensional extra-large elliptical channels with a diameter up to 11 Å able to host bulky guest species, and the particular organic structure-directing agent used for the synthesis (1,8-bis(dimethylamino)naphthalene, DMAN), which efficiently fills the IFO pores, and is itself a photoactive molecule with interesting fluorescence properties in the blue range of the visible spectrum, thus providing a densely-incorporated donor species for FRET processes. Besides, occlusion of DMAN dye in the framework triggers a notable improvement of its fluorescence properties by confinement effect. To extend the action of the material and to mimic processes such as photosynthesis in which FRET is essential, two robust laser dyes with bulky size, rhodamine 123 and Nile Blue, have been encapsulated for the first time in a zeolitic framework, together with DMAN, in a straightforward one-pot synthesis. Thus, photoactive systems with emission in the entire visible range have been achieved due to a partial FRET between organic chromophores protected in a rigid aluminophosphate matrix.

Styryl dyes are generally poor fluorescent molecules inherited from their flexible molecular structures. However, their emissive properties can be boosted by restricting their molecular motions. A tight confinement into inorganic molecular sieves is a good strategy to yield highly fluorescent hybrid systems. In this work, we compare the confinement effect of two Mg-aluminophosphate zeotypes with distinct pore systems (the AEL framework, a one-dimensional channeled structure with elliptical pores of 6.5 Å × 4.0 Å, and the CHA framework, composed of large cavities of 6.7 Å × 10.0 Å connected by eight-ring narrower windows) for the encapsulation of 4-DASPI styryl dye (trans-4-[4-(Dimethylamino)styryl]-1-methylpyridinium iodide). The resultant hybrid systems display significantly improved photophysical features compared to 4-DASPI in solution as a result of tight confinement in both host inorganic frameworks. Molecular simulations reveal a tighter confinement of 4-DASPI in the elliptical channels of AEL, explaining its excellent photophysical properties. On the other hand, a singular arrangement of 4-DASPI dye is found when confined within the cavity-based CHA framework, where the 4-DASPI molecule spans along two adjacent cavities, with each aromatic ring sitting on these adjacent cavities and the polymethine chain residing within the narrower eight-ring window. However, despite the singularity of this host–guest arrangement, it provides less tight confinement for 4-DASPI than AEL, resulting in a slightly lower quantum yield.

[EN] In this work, the asymmetric catalytic activity of the recently discovered GTM-3 chiral zeolite is systematically explored for the ring-opening of trans-stilbene oxide using alcohols of different size as nucleophiles. Catalytic results show a volcano-type curve with a clear maximum enantioselective activity for a specific linear alcohol size of 4C (1-butanol); this is perfectly reproduced in opposite sign for GTM-3 catalysts obtained with the antipode of the structure-directing agent. Such trend evidences that a proper chiral host-guest size match must be established between the reactants and/or transition states and the chiral confined space provided by the zeolite framework in order for the zeolite catalyst to manifest its chirality. Moreover, secondary alcohols, bulkier in size, give higher enantioselectivities than their linear counterparts. On the other hand, variation of the reaction conditions enables to maximize the enantioselectivity of the reaction: in particular, variation of the concentration of the epoxide displays a strong influence, notably improving the enantiomeric excess obtained when the concentration of the epoxide is reduced. Modification of the reaction temperature also influences the enantiomeric excess, and especially, the selectivity to the different products. Our results suggest that if a proper chiral host-guest match is established within the confined chiral nanospace of the zeolite framework, then the enantioselectivity as well as the selectivity to the chiral products is maximized, which indeed can be manipulated through variations of the reaction conditions, leading to unprecedented enantiomeric excess values up to 51%.

Styryl dyes are generally poor fluorescent molecules inherited from their flexible molecular structures. However, their emissive properties can be boosted by restricting their molecular motions. A tight confinement into inorganic molecular sieves is a good strategy to yield highly fluorescent hybrid systems. In this work, we compare the confinement effect of two Mg-aluminophosphate zeotypes with distinct pore systems (the AEL framework, a one-dimensional channeled structure with elliptical pores of 6.5 Å × 4.0 Å, and the CHA framework, composed of large cavities of 6.7 Å × 10.0 Å connected by eight-ring narrower windows) for the encapsulation of 4-DASPI styryl dye (trans-4-[4-(Dimethylamino)styryl]-1-methylpyridinium iodide). The resultant hybrid systems display significantly improved photophysical features compared to 4-DASPI in solution as a result of tight confinement in both host inorganic frameworks. Molecular simulations reveal a tighter confinement of 4-DASPI in the elliptical channels of AEL, explaining its excellent photophysical properties. On the other hand, a singular arrangement of 4-DASPI dye is found when confined within the cavity-based CHA framework, where the 4-DASPI molecule spans along two adjacent cavities, with each aromatic ring sitting on these adjacent cavities and the polymethine chain residing within the narrower eight-ring window. However, despite the singularity of this host–guest arrangement, it provides less tight confinement for 4-DASPI than AEL, resulting in a slightly lower quantum yield.

Jeffrey Raff Traductor: Francisco López Martín. Girona, Atalanta, 2022. 336 páginas. ISBN: 978-84-124315-1-3. PVP: 27 €

María Pandiello Editorial La Felguera, 2022. 289 páginas. ISBN: 978-84-124669-7-3. PVP: 24,90 €

Gold nanospecies produced by a historically inspired two-liquid phase system were immobilized on plate-like mesoporous silica, SBA-15, functionalized with mercaptopropyl groups by a post-synthesis method, and the resulting materials were tested in the oxidation of cyclohexene with molecular oxygen at atmospheric pressure. The main purpose of this approach was to compare the physicochemical properties and catalytic performance of these materials with those of previously reported related materials functionalized by in situ methods during synthesis. In addition, catalytic tests under ambient lighting and darkness and also in the presence and absence of the initiator tert-butyl hydroperoxide (TBHP) were carried out. The samples were characterized by chemical analysis, N2 adsorption/desorption, TGA, SEM, HRTEM, UV-vis spectroscopy and XPS. Gold nanoclusters and isolated gold atoms but no AuNPs were found in the catalysts (0.31–2.69 wt.% of gold). The XPS shows that nearly 60% of the -SH groups (1.33 wt.% of S) were oxidized to sulphonic groups upon gold immobilization. The AuNCs and isolated gold atoms evolved in the the reaction medium to form AuNPs. The activity of the samples was lower than that of the catalysts supported on related S-bearing SBA-15 functionalized in situ, which was attributed to their different Au/S ratios, which in turn regulated the evolutionary process of the gold species during the reaction. The catalysts turned out to be inactive in darkness, which evidences that the cyclohexene oxidation carried out at ambient illumination is actually photocatalyzed by the AuNPs formed in situ during the reaction. The TBHP initiator is required to obtain the activity in order to counteract the inhibitors of cyclohexene auto-oxidation present in the commercial reagent. On the other hand, no major differences in the selectivity among the different catalysts and reactions were observed, with 2-cyclohexen-1-one and 2-cyclohexen-1-ol resulting from the allylic oxida

Iron modified mesoporous silica structures were achieved from biomass-derived renewable molding agents (glyceryl monostearate and glycerol) and can become potential substitutes for conventional mesoporous catalysts synthesized from petrochemical-derived precursors. These materials were prepared by different methods (wet impregnation with iron contents of 2.5, 5, 10 and 20% w/w and direct incorporation using a molar ratio Si/Fe = 20) and characterized by XRD, N2 adsorption and desorption isotherms, UVvis-DR and ICP. By using these solid as heterogeneous catalysts in the wet oxidation reaction of the herbicide glyphosate with air under extremely mild reaction conditions (atmospheric pressure and room temperature), herbicide degradation/fragmentation levels of around 70% were achieved. The methodology employed for the synthesis played a key role in the development of the structure and dispersion of Fe species as well as in the stability of the catalytic system. In this way, an advanced technology with low environmental impact for the treatment of a pollutant of great concern at the global level was developed, which adds sustainability to the chemical industry from the use of residual glycerol and/or glyceryl monostearate in the catalyst synthesis. © 2023 Elsevier Inc.