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Magnetic Core–Shell to Yolk–Shell Structures in Palladium‐Catalyzed Suzuki–Miyaura Reactions: Heterogeneous versus Homogeneous Nature
Author(s) -
Li Yinle,
Zhang Zhuqing,
Fan Tao,
Li Xiaoguang,
Ji Jin,
Dong Pei,
Baines Robert,
Shen Jianfeng,
Ye Mingxin
Publication year - 2016
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.201600094
Subject(s) - catalysis , palladium , chemical engineering , heterogeneous catalysis , mesoporous silica , materials science , mesoporous material , chemistry , nanoparticle , cerium oxide , inorganic chemistry , nanotechnology , organic chemistry , engineering
This study describes a comparative investigation on the heterogeneous versus homogeneous nature of the Pd‐catalyzed Suzuki–Miyaura cross‐coupling reaction mechanism with specific magnetic hierarchical core–shell and yolk–shell structures. The hierarchical core–shell Fe 3 O 4 @SiO 2 ‐Pd@ m CeO 2 ( m =mesoporous) catalyst contains a core of nonporous silica‐sheltered magnetite (Fe 3 O 4 ) nanoparticles (NPs), a transition layer of active palladium (Pd) NPs, and an outer shell of porous ceria (CeO 2 ). The magnetic yolk–shell Fe 3 O 4 @ h ‐Pd@ m CeO 2 ( h =hollow) catalyst was prepared by selectively etching the nonporous silica interlayers. Notably, the results of the hot‐filtration heterogeneity test, the effect of Pd concentration, and solid‐phase poisoning, indicate that the two kinds of catalysts function in Pd‐catalyzed Suzuki–Miyaura cross‐coupling reactions through different catalytic mechanisms. Moreover, both catalysts demonstrated better catalytic activity than the Fe 3 O 4 @SiO 2 ‐Pd catalyst. This finding can be ascribed to the outermost CeO 2 shell having a high concentration of trivalent cerium and oxygen vacancies, which gives rise to the increased electron density of Pd NPs, and a faster rate‐determining step in the oxidative addition reaction for the Suzuki reaction. In addition, we propose a feasible mechanism elucidating the synergistic effect between the supporting CeO 2 and active species.