Fabrication of Ag/γ-Fe₂O₃@TiO₂hollow magnetic core–shell nanospheres as highly efficient catalysts for the synthesis of β-enaminones

Abstract

a Herein, we describe a method to prepare hollow magnetic mesoporous spheres catalyst (Ag/γ-Fe2O3@meso-TiO2) . The core-shell strategy efficiently prevents the aggregation of Ag NPs in the high temperature calcination process and the leaching of Ag NPs for the catalytic reaction in a liquid phase. The catalyst is characterized by TEM, XRD, ICP-AES. Moreover, the catalyst exhibited improved activity for synthesis of β-enaminones, and it could be easily recovered by an external magnet from the reaction mixture and recycled five times without any significant loss in activity.

Industrial-Quality Graphene Oxide Switched Highly Efficient Metal- and Solvent-Free Synthesis of β-Ketoenamines under Feasible Conditions

“…Density functional theory (DFT) calcinations are very useful to determine the suitable reaction pathway of catalytic reactions. − DFT calculations were previously performed for the synthesis of β-ketoenamines by Babu and co-workers . The computed result confirms that the enol form of acetyl acetone is more stable and reactive than the diketone from.…”

“…The activity of IQGO is better or comparable with other reported metal and nonmetal catalysts including Cu/AlO-(OH), 27 NaAuCl 4 , 29 Ag nanoparticles, 28,30 Mg(ClO 4 ) 2 , 31 CoCl 2 •6H 2 O, 32 Zn(OAc) 2 •2H 2 O, 33 CeCl 3 •7H 2 O, 34 Zn-(ClO 4 ) 2 •6H 2 O, 35 ZrCl 4 , 36 SnCl 4 , 37 Cu nanoparticles, 38 Cu(II) nitrate trihydrate, 39 ZrOCl 2 •8H 2 O, 40 Ag/γ-Fe 2 O 3 @TiO 2 , 46 and GO-SnO 2 47 InBr 3 . 41 The better activity is obviously due to the three main reasons: (1) the higher surface area of IQGO (767 m 2 /g), (2) presence of oxygen functionalities (CO, −COOH, COH, and −COC−) and interconnected pores on IQGO, and (3) higher level of dispersion of IQGO in the reaction mixture.…”

Enhanced Catalytic Performances for Guaiacol Aqueous Phase Hydrogenation over Ruthenium Supported on Mesoporous TiO2 Hollow Spheres Embedded with SiO2 Nanoparticles

“…Due to its favorable properties, mesoporous TiO 2 has attracted increasing research interest and has been gradually used in liquid catalytic hydrogenation. Huo et al . prepared hollow Ag/g‐Fe 2 O 3 @TiO 2 magnetic core–shells in the catalyst synthesis of b‐enamino ketones or esters from b‐dicarbonyl compounds in methanol solvents; the results suggested that the hollow magnetic mesoporous structure can effectively improve catalytic activity.…”

Toward “Green” Hybrid Materials: Core–Shell Particles with Enhanced Impact Energy Absorbing Ability

“… 6 Structured CS particles combine the characteristics and properties of the shell and the core, where the surface properties of the shell are translated to the core, imparting new functionality to the final structure, causing a synergistic effect. 7 − 9 Accordingly, CS particles have been extensively used in a number of applications such as surface coatings, 10 catalysis, 11 , 12 drug delivery systems 13 − 15 and more recently as impact modifiers. 16 − 19 …”

“…Among those, particulate “green” composites have gained much attention as unique properties, by synergetic combination of the diverse components on the molecular scale, can be achieved. − In light of this, the creation and usage of functional particles and particles with core–shell (CS) structure has become an attractive choice as components in advanced materials . Structured CS particles combine the characteristics and properties of the shell and the core, where the surface properties of the shell are translated to the core, imparting new functionality to the final structure, causing a synergistic effect. − Accordingly, CS particles have been extensively used in a number of applications such as surface coatings, catalysis, , drug delivery systems − and more recently as impact modifiers. − …”