Baeyer–Villiger oxidation of cyclic ketones using Fe containing MCM-48 cubic mesoporous materials

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.

Cobalt-Tetraamide-Phthalocyanine Immobilized on Fe3O4/Chitosan Microspheres as an Efficient Catalyst for Baeyer-Villiger Oxidation

Cobalt-Tetraamide-Phthalocyanine (CoTaPc) immobilized onto magnetic Fe₃O₄ chitosan microspheres (Fe₃O₄/CTO) was synthesized via a simple immersion method, which is an efficient catalyst for the oxidation of cyclic ketones to lactones with O₂/benzaldehyde as the oxidant. The CoTaPc-Fe₃O₄/CTO catalyst was applied for the first time in the Baeyer-Villiger (B-V) oxidation reaction. Characterization results obtained from X-ray diffraction, UV-vis, Fourier transform infrared, and scanning electron microscopy showed that the combination of CoTaPc and magnetic Fe₃O₄/CTO microspheres was achieved. The catalyst could be easily separated from the reaction system with an external magnet and reused several times without the remarkable loss of activity. In addition, a possible radical mechanism for the B-V oxidation in this catalytic system is proposed and verified by controlled experiments.

Keggin-Type Heteropoly Salts as Bifunctional Catalysts in Aerobic Baeyer-Villiger Oxidation

The cobalt, manganese, and iron salts of tungstophosphoric or molybdophosphoric acid with growing content of metals were applied for the first time as catalysts in the Baeyer-Villiger (BV) oxidation of cyclohexanone to ε-caprolactone with molecular oxygen. The catalysts were characterized with Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), and ethanol decomposition reaction. Introduction of transition metals into the heteropoly structure increases the activity of resulting heteropoly salts in comparison with parent heteropolyacids. It was shown that the most active catalysts are salts of the heteropoly salts with one metal atom introduced and one proton left (HMPX) type, (where M = Co, Fe, Mn, and X = W, Mo) with the metal to proton ratio equal one. Among all of the studied catalysts, the highest catalytic activity was observed for HCoPW. The effect indicates that both the acidic and redox properties are required to achieve the best performance. The Baeyer-Villiger (BV) oxidation mechanism proposed identifies the participation of heteropoly compounds in three steps of the investigated reaction: oxidation of aldehyde to peracid (redox function), activation of carbonyl group (Lewis acidity), and decomposition of the Criegee adduct to ε-caprolactone (Brønsted acidity).

Fe–SBA-15 catalyzed synthesis of 2-alkoxyimidazo[1,2-a]pyridines and screening of their in silico selectivity and binding affinity to biological targets

Regioselective synthesis of 2-alkoxyimidazopyridines by Fe-SBA-15 and screening of their in silico binding affinity to biological targets.

The dual role of micelles as templates and reducing agents for the fabrication of catalytically active hollow silver nanospheres

A simple and efficient protocol for fabrication of colloidal hollow Ag nanospheres of size less than 30 nm using a triblock copolymer in the absence of any reducing agent is reported, which showed excellent catalytic activity in the Baeyer–Villiger oxidation reaction.

Recent developments in liquid-phase selective oxidation using environmentally benign oxidants and mesoporous metal silicates

This Perspective article surveys recent advances in the synthesis of mesoporous transition-metal-containing silicate materials and their use for the liquid-phase selective oxidation of organic compounds with environmentally friendly oxidants – molecular oxygen, hydrogen peroxide and organic hydroperoxides.

Catalytic applications of mesoporous silica-based materials

Mesoporous materials featuring high surface areas (>600m2g−1), narrow pore size distribution and tuneable pores diameters (>2nm), have attracted a great deal of attention in recent years due to their promising properties and applications in various areas including adsorption, separation, drug delivery, sensing and catalysis. Catalytic applications of such materials have been extended to numerous processes and reactions which range from acid catalysis (alkylations, acylations, esterifications, biodiesel production, etc.) to redox chemistries (oxidation of alcohols, alkenes, sulfides and hydrogenations of acids, aldehydes and ketones and alkenes/alkynes). In this chapter, we aim to provide an overview on the utilisation of mesoporous materials in heterogeneous catalysis, with special emphasis on acid and redox catalysed processes.