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Protecting Mg-sites from hydration by embedding magnesium-aluminium layered double hydroxide in halloysite and using as pickering catalysts in Baeyer-Villiger oxidation
Abstract A facile strategy was developed via thermal treatment to get hierarchically structured magnesium-aluminium layered double hydroxide (MgAl-LDH) selectively loaded on the inner and external surfaces of halloysite nanotubes, respectively. The loaded MgAl-LDH was found to have active centers for Baeyer-Villiger (BV) oxidation that was protected from hydration by embedding in halloysite lumens. The BV oxidation of cyclohexanone was observed to have better performance by using the halloysite impregnated MgAl-LDH (MgAl-LDH@Hal) as catalysts than that of external surface modified MgAl-LDH (MgAl-LDH@Hal600). A conversion 57.0% of cyclohexanone was achieved, and the yield of ε-caprolactone was 22.0% when the MgAl-LDH@Hal was used as catalysts. Density Functional Theory (DFT) calculations as well as high-resolution of X-ray photoelectron spectrum (XPS) measurements revealed the charge depletion occurred in the Mg-sites of sample MgAl-LDH@Hal in comparison with MgAl-LDH@Hal600, which benefited the activation of H2O2 oxidants, and thus assisting the BV reaction. The prepared composites were able to work as phase-transfer catalysts as Pickering emulsions in oxidation of cyclohexanone.
Graphical Abstract The loaded MgAl-LDH was found to have active centers for Baeyer-Villiger (BV) oxidation that was able to be protected from hydration by embedding in halloysite lumens. Display Omitted
Highlights MgAl-LDH was selectively loaded on the inner/external surface of halloysite. Higher conversion and better cyclability of cyclohexanone were achieved. Sample MgAl-LDH@Hal displayed phase-transfer behaviors in catalytic process. DFT elucidated the electron-depletion Mg-sites readily protected by halloysite.
Protecting Mg-sites from hydration by embedding magnesium-aluminium layered double hydroxide in halloysite and using as pickering catalysts in Baeyer-Villiger oxidation
Abstract A facile strategy was developed via thermal treatment to get hierarchically structured magnesium-aluminium layered double hydroxide (MgAl-LDH) selectively loaded on the inner and external surfaces of halloysite nanotubes, respectively. The loaded MgAl-LDH was found to have active centers for Baeyer-Villiger (BV) oxidation that was protected from hydration by embedding in halloysite lumens. The BV oxidation of cyclohexanone was observed to have better performance by using the halloysite impregnated MgAl-LDH (MgAl-LDH@Hal) as catalysts than that of external surface modified MgAl-LDH (MgAl-LDH@Hal600). A conversion 57.0% of cyclohexanone was achieved, and the yield of ε-caprolactone was 22.0% when the MgAl-LDH@Hal was used as catalysts. Density Functional Theory (DFT) calculations as well as high-resolution of X-ray photoelectron spectrum (XPS) measurements revealed the charge depletion occurred in the Mg-sites of sample MgAl-LDH@Hal in comparison with MgAl-LDH@Hal600, which benefited the activation of H2O2 oxidants, and thus assisting the BV reaction. The prepared composites were able to work as phase-transfer catalysts as Pickering emulsions in oxidation of cyclohexanone.
Graphical Abstract The loaded MgAl-LDH was found to have active centers for Baeyer-Villiger (BV) oxidation that was able to be protected from hydration by embedding in halloysite lumens. Display Omitted
Highlights MgAl-LDH was selectively loaded on the inner/external surface of halloysite. Higher conversion and better cyclability of cyclohexanone were achieved. Sample MgAl-LDH@Hal displayed phase-transfer behaviors in catalytic process. DFT elucidated the electron-depletion Mg-sites readily protected by halloysite.
Protecting Mg-sites from hydration by embedding magnesium-aluminium layered double hydroxide in halloysite and using as pickering catalysts in Baeyer-Villiger oxidation
Peng, Jiangtao (author) / Qu, Haoyang (author) / Si, Jiwen (author) / Li, Shucheng (author) / Zhao, Longxin (author) / Wang, Yuxuan (author) / Liang, Qing (author) / Zhang, Wei (author) / Wei, Cundi (author) / Li, Wenqing (author)
Applied Clay Science ; 251
2024-03-03
Article (Journal)
Electronic Resource
English
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