From Core–Shell to Yolk–Shell: Improved Catalytic Performance toward CoFe₂O₄@ Hollow@ Mesoporous TiO₂ toward Selective Oxidation of Styrene

Abstract

Developing catalysts with structural characteristics, reusability, cost-effectiveness, environmental friendliness, and preferable catalytic performance is challenging for the selective oxidation of alkenes. In this article, we report the synthesis of magnetically separable CoFe 2 O 4 @ hollow@ mesoporous TiO 2 with yolk−shell structure, which could be used as a selectivity variable and stable catalyst for the selective oxidation of styrene, yielding different oxidation products. With oxygen as the oxidant, epoxidation of styrene occurred, affording an epoxy group. With hydrogen peroxide as the oxidant, oxidative cleavage of double bonds in the styrene and further oxidation were conducted, affording a carboxylic acid group. Compared with pristine CoFe 2 O 4 , TiO 2 , and CoFe 2 O 4 /TiO 2 core−shell structure, the CoFe 2 O 4 @ hollow@ mesoporous TiO 2 with yolk−shell structure was found to be a more efficient catalyst for the oxidation of styrene. Meanwhile, the kinetic analysis and activation energies of different catalysts were investigated to illustrate the relationship between the performance and the structure of catalysts. Active radical scavenging experiments were conducted to figure out the dominant radicals in the oxidation reaction. The corresponding possible reaction mechanisms of the oxidation reaction were also proposed.

Perovskite LaSrCoFeO6 Oxide Enabled Visible Light Catalytic Aerobic Epoxidation of Styrene

“…This is the first example of employing LSCF oxides as superior visible-light catalyst for epoxidation of styrene just using molecular oxygen as the oxidant. Relative with these (7.4 ~37.5 mmol • g cat À 1 • h À 1 ) of the reported catalysts coupled with either oxygen or TBHP [6,20,[33][34][35][36] (Table 1, entries 12-16), LSCF catalyst reported in this work shows the highest reaction rate of ~50 mmol • g cat À 1 • h À 1 (Table 1, entry 7). Additionally, LSCF catalyst even shows the considerable catalytic performance under visible light compared with the activity of LSCF-1.6 catalyst under ultraviolet light in our previous study.…”

Advanced metal oxide-based nanocatalysts for the oxidative synthesis of fine chemicals

“…Similarly, Liu et al reported the preparation of a CoFe 2 O 4 @hollow@mesoporous TiO 2 catalyst for the selective oxidation of styrene. 138 It was observed that styrene oxide and benzoic acid were selectively obtained upon the use of oxygen and hydrogen peroxide as the oxidant, respectively. Indeed, it is evident from the literature that surfaceengineered metal oxide nanocomposites having Brønsted acid (proton donating) and Lewis acid (electron withdrawing) sites are nowadays more often employed in industrial catalysis.…”

Confinement of nano-gold in 3D hierarchically structured gadolinium-doped ceria mesocrystal: synergistic effect of chemical composition and structural hierarchy in CO and propane oxidation

“…16 Structural hierarchy relates to the repetitive combination of units, forming superstructures composed of mutually ordered nanoparticles (mesocrystals) 22 or materials with distinguished levels of structural units, forming complex structures 23 (e.g., hollow nano-cone-constructed ceria, 24 ceria nanobundles, 25 and 3D flowerlike ceria). 26 Compositional hierarchy refers to the spatial distribution of various building units differing in composition (e.g., core-shell mesoporous nanospheres 27 and hollow@mesoporous yolk-shell structure), 28 and the porous hierarchy involves the distribution of multimodal pores in a material (e.g., micromacroporous zeolites). 29 The ensemble of nanoparticles that form a higher-order hierarchical structure may possess unique properties that differ from those of individual nanoparticles and corresponding bulk samples, which may contribute to its catalytic performance.…”

“…26 Compositional hierarchy refers to the spatial distribution of various building units differing in composition ( e.g. , core–shell mesoporous nanospheres 27 and hollow@mesoporous yolk–shell structure), 28 and the porous hierarchy involves the distribution of multimodal pores in a material ( e.g. , micro–macroporous zeolites).…”