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Stability of Immobilization of Bipyridine‐proline on Zn‐Modified Bimodal Mesoporous Silicas and Recyclable Catalytic Performance in Asymmetric Aldol Reaction
Author(s) -
Zhang Yajing,
Sun Jihong,
Bai Shiyang,
Zhao Hongwu,
Wu Xia,
Panezai Hamida
Publication year - 2019
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201804000
Subject(s) - catalysis , mesoporous material , chemistry , small angle x ray scattering , aldol reaction , sorption , materials science , nuclear chemistry , chemical engineering , organic chemistry , physics , adsorption , scattering , optics , engineering
The organic‐inorganic mesoporous materials (ZZnBMMs) were successfully synthesized by Zn‐grafting into the surface of bimodal mesoporous silicas (BMMs) via covalent bond, and then immobilization of (2 S,2’S)‐N,N’‐([2,2’‐bipyridine]‐3,3’‐diyl)bis(pyrrolidine‐2‐carboxamide) (Z) onto the Zn‐modified BMMs through coordination method. The influences of washed parameters such as various solvents (petroleum ether, CH 2 Cl 2 , CH 3 OH, or DMSO) and pretreated temperature on the structural stability of obtained ZZnBMMs were investigated thoroughly, which were extensively characterized by means of XRD patterns, UV‐vis and FT‐IR spectra, N 2 sorption isotherms, SEM images, and SAXS patterns. The results showed that petroleum ether could be acted as optimum solvent for washing ZZnBMMs when pre‐treated temperature was around 20 °C. The SAXS patterns evidently demonstrated that ZZnBMMs before and after washing presented the fractal features, suggesting their surface roughness and structural irregularities, in which, the mass fractal ( D m ) values were gradually decreased along with not only the increased polarity of used solvents (petroleum ether, CH 2 Cl 2 , CH 3 OH, and DMSO), but also enhanced washing temperature of from 20–60 °C and prolonged time of from 4–168 hrs. Furthermore, the ZZnBMMs as a heterogeneous catalyst for asymmetric aldol reaction exhibited the recycled (at least 6 times) catalytic performances with high efficiency (around 92.1% yield) and good selectivity (up to 68% ee).