Streamlined synthesis of iron and cobalt loaded MCM-48: High-performance heterogeneous catalysts for selective liquid-phase oxidation of toluene to benzaldehyde

Hydrothermal synthesis of MCM-48 molecular sieves featuring the incorporation of both iron and cobalt with Si/M ratios of 20, 40 and 80 (where M represents either iron or cobalt) was performed using tetraethyl orthosilicate as the silica source and cetyltrimethylammonium bromide as a template. To gain a comprehensive understanding of the synthesized materials, these were thoroughly characterized using various techniques, including XRD, XPS, UV-Vis (DRS), FT-IR, N2 adsorption-desorption analysis, SEM with EDX, TEM, TGA and NH3-TPD analysis. XRD analysis revealed the presence of well-ordered MCM-48 structure in the metal-incorporated materials, while XPS and UV-Vis DRS confirmed the successful partial incorporation of metal ions precisely in their desired tetrahedral coordination within the framework. To assess their catalytic performance, we studied the activity and selectivity of these catalysts in liquid phase oxidation of toluene using tert-butyl hydroperoxide as the oxidant. Under optimized conditions, employing a 6% (w/w) Fe-MCM-48 (40) catalyst and maintaining a toluene to oxidant molar ratio of 1:3 at 353 K in a solvent-free environment for 8 h, the oxidation reaction resulted in the formation of benzaldehyde (88.1%) as the major product and benzyl alcohol (11.9%) as the minor product.

Oxidation of BINOLs by Hypervalent Iodine Reagents: Facile Synthesis of Xanthenes and Lactones

Xanthene derivatives have broad applications in medicines, fluorescent probes, dyes, food additives, etc. Therefore, much attention was focused on developing the synthetic methods to prepare these compounds. Binaphthyl‐based xanthene derivatives were prepared through the oxidation of BINOLs promoted by the hypervalent iodine reagent iodosylbenzene (PhIO). Nine‐membered lactones were obtained through a similar oxidative reaction when iodoxybenzene (PhIO₂) was used. Additionally, one‐pot reactions of BINOLs, PhIO and nucleophiles such as alcohols and amines were also investigated to provide alkoxylated products and amides in good to excellent yields.

Synthesis of Au@MOF core-shell hybrids for enhanced photodynamic/photothermal therapy

Photodynamic/photothermal therapy (PDT/PTT) has become a research focus of cancer treatment due to the non-invasiveness, spatio-temporal controllability, and effectiveness of repeated treatment. Here, Au@MOF core-shell hybrids were designed and constructed by the layer-by-layer method, and the thickness of the MOF shell can be adjusted by controlling the coordination reaction between the layers. Au nanorod cores mainly produce the PTT effect due to their strong absorbance at 650 nm. The porphyrin ligand in the MOF shell can convert O₂ into ¹O₂ under light conditions, resulting in a high PDT effect. Moreover, the metal node Fe₃O(OAc)₆(H₂O)₃⁺ cluster of the MOF can catalyze the decomposition of H₂O₂ into O₂ to overcome the hypoxic environment of tumors, which further improves the effect of PDT. The combination of the porphyrin ligand in the MOF structure and Au nanorods has promoted the synergistic effects of PDT/PTT. As expected, the results confirmed that Au@MOF hybrids showed no obvious biotoxicity in both cells and animal experiments, and exhibited good biocompatibility. With the synergistic effects of PDT/PTT, cancer cells could be effectively killed and tumor growth could be inhibited. In addition, the modification of folic acid on the surface of Au@MOF can further enrich the hybrids at the tumor site and enhance the inhibitory effect on tumors. These studies have proved that PDT and PTT can be effectively combined and have greater advantages in enhancing the treatment of tumors.

An insight into the catalytic activity of palladium Schiff-base complexes towards the Heck coupling reaction: routes via encapsulation in zeolite-Y

A small set of palladium Schiff-base complexes were synthesized and entrapped in the supercage of zeolite-Y. All these novel complexes in both states were systematically characterized with the help of different characterization tools like XRD, SEM-EDS, thermal analysis, XPS, IR, electronic spectroscopic and theoretical studies. These systems were thoroughly studied for their catalytic activities towards the Heck coupling reaction between bromobenzene and styrene. The aim was to meticulously compare the performance of the homogeneous catalysts, i.e., neat palladium Schiff-base complexes with that of their heterogeneous encapsulated analogs. The experimental as well as theoretical electronic structure studies suggested significant structural modification of the guest Pd(ii)-Schiff-base complexes after encapsulation in zeolite Y. These complexes manifested modified catalytic activities towards the Heck coupling reaction. The theoretical studies reinforced the correlation between the modified catalytic properties and structural alteration of these complexes on encapsulation. These heterogeneous catalysts essentially demonstrated the benefits of easy separation and reusability as compared to the homogeneous analogues.

Pd/Cu-Oxide Nanoconjugate at Zeolite-Y Crystallite Crafting the Mesoporous Channels for Selective Oxidation of Benzyl-Alcohols

Solid-state grinding of palladium and copper salts allowed the growth of palladium/copper oxide interface at the zeolite-Y surface. The hybrid nanostructured material was used as reusable heterogeneous catalyst for selective oxidation of various benzyl alcohols. The large surface area provided by the zeolite-Y matrix highly influenced the catalytic activity, as well as the recyclability of the synthesized catalyst. Impregnation of PdO-CuO nanoparticles on zeolite crystallite leads to the generation of mesoporous channel that probably prevented the leaching of the metal-oxide nanoparticles and endorsed high mass transfer. Formation of mesoporous channel at the external surface of zeolite-Y was evident from transmission electron microscopy and surface area analysis. PdO-CuO nanoparticles were found to be within the range of 2-5 nm. The surface area of PdO-CuO-Y catalyst was found to be much lower than parent zeolite-Y. The decrease in surface area as well as the presence of hysteresis loop in the N₂-adsoprtion isotherm further suggested successful encapsulation of PdO-CuO nanoparticles via the mesoporous channel formation. The high positive shifting in binding energy in both Pd and Cu was attributed to the influence of zeolite-Y framework on lattice contraction of metal oxides via confinement effect. PdO-CuO-Y catalyst was found to oxidize benzyl alcohol with 99% selectivity. On subjecting to microwave irradiation the same oxidation reaction was found to occur at ambient condition giving same conversion and selectivity.

Shallow V-Shape Nanostructured Pit Arrays in Germanium Using Aqua Regia Electroless Chemical Etching

Due to its high refractive index, reflectance is often a problem when using Germanium for optoelectronic devices integration. In this work, we propose an effective and low-cost nano-texturing method for considerably reducing the reflectance of bulk Germanium. To do so, uniform V-shape pit arrays are produced by wet electroless chemical etching in a 3:1 volume ratio of highly-concentrated hydrochloridric and nitric acids or so-called aqua regia bath using immersion times ranging from 5 to 60 min. The resulting pit morphology, the crystalline structure of the surface and the changes in surface chemistry after nano-patterning are all investigated. Finally, broadband near-infrared reflectance measurements confirm a significant reduction using this simple wet etching protocol, while maintaining a crystalline, dioxide-free, and hydrogen-passivated surface. It is important to mention that reflectance could be further reduced using deeper pits. However, most optoelectronic applications such as photodetectors and solar cells require relatively shallow patterning of the Germanium to allow formation of a pn-junction close to the surface.

Surface PEG Grafting Density Determines Magnetic Relaxation Properties of Gd-Loaded Porous Nanoparticles for MR Imaging Applications

Surface PEGylation of nanoparticles designed for biomedical applications is a common and straightforward way to stabilize the materials for in vivo administration and to increase their circulation time. This strategy becomes less trivial when MRI active porous nanomaterials are concerned as their function relies on water/proton-exchange between the pores and bulk water. Here we present a comprehensive study on the effects of PEGylation on the relaxometric properties of nanozeolite LTL (dimensions of 20 × 40 nm) ion-exchanged with paramagnetic GdIII ions. We evidence that as long as the surface grafting density of the PEG chains does not exceed the "mushroom" regime (conjugation of up to 6.2 wt % of PEG), Gd-LTL retains a remarkable longitudinal relaxivity (38 s-1 mM-1 at 7 T and 25 °C) as well as the pH-dependence of the longitudinal and transverse relaxation times. At higher PEG content, the more compact PEG layer (brush regime) limits proton/water diffusion and exchange between the interior of LTL and the bulk, with detrimental consequences on relaxivity. Furthermore, PEGylation of Gd-LTL dramatically decreases the leakage of toxic GdIII ions in biological media and in the presence of competing anions, which together with minimal cytotoxicity renders these materials promising probes for MRI applications.

Chiral modification of copper exchanged zeolite-Y with cinchonidine and its application in the asymmetric Henry reaction

(−)-Cinchonidine is being encapsulated inside copper exchanged zeolite-Y and used as heterogeneous catalyst for the asymmetric Henry reaction.

Oxidative coupling of 2-naphthol to (R)/(S)-BINOL by MCM-41 supported Mn-chiral Schiff base complexes

Conversion of 2-naphthol toC2-symmetric BINOL is achieved in 91% ee in the presence of an Mn-Schiff base chiral catalyst supported on MCM-41.

New photocatalyst for allylic aliphatic C–H bond activation and degradation of organic pollutants: Schiff base Ti(iv) complexes

Ti(iv) Schiff base complex oxide photocatalysts with high stability for oxidative-cyclization and photodegradation of methylene blue dye under visible light irradiation.