Comparison of mesoporous fractal characteristics of silica-supported organocatalysts derived from bipyridine-proline and resultant effects on the catalytic asymmetric aldol performances.
Comparison of mesoporous fractal characteristics of silica-supported organocatalysts derived from bipyridine-proline and resultant effects on the catalytic asymmetric aldol performances.
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二氧化硅负载联吡啶-脯氨酸有机催化剂的介孔分形特征比较及其对催化不对称羟醛性能的影响
DOI：
10.1039/d2ra00971d
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发表时间：
2022-03-31
期刊：
影响因子：
3.9
通讯作者：
Sun J
中科院分区：
文献类型：
--
作者：
Xu G;Bing L;Jia B;Bai S;Sun J
通过共价键和配位的方法，将三种联吡啶-脯氨酸手性配体作为高活性物种成功地引入到Zn修饰的介孔氧化硅纳米材料（BSiO 2，MCM-41，SBA-15）上。通过XRD、SEM/TEM、TGA、FT-IR和UV-Vis等手段对它们的微观结构和物理化学性能进行了表征。特别是，它们的分形特征，对距离分布函数，和Porod图进行了全面评估的SAXS数据的基础上。同时评价了它们对对硝基苯甲醛和环己酮不对称羟醛缩合反应的催化性能。结果表明，具有短蠕虫状孔道结构的双峰BMMs基样品同时具有质量和表面分形特征，而具有长程有序结构的MCM-41和SBA-15基样品仅具有表面分形特征。考察了介孔材料的结构、手性配体的结构以及醛的分子体积等因素对催化活性和立体选择性的影响。结果表明，与以Z为催化剂的均相催化体系相比，该催化剂具有较好的活性（产率）和较好的立体选择性（dr和ee）。特别地，Z-固定化的非均相催化剂的第三循环催化性能保持高催化产率（约80%）和28%的ee值。这些多相催化剂的分形特征与其催化活性之间的本质关系很好地解释了这些现象。通过小角X射线散射法等表征手段，深入探讨了分形演化与催化性能之间的关系。从而证明了分形理论的适用性和可靠性。
Three kinds of the bipyridine-proline chiral ligands as highly active species were successfully introduced on Zn-modified mesoporous silica nanomaterials (BMMs, MCM-41, and SBA-15) via the covalent attachment and coordination methods. Their microstructural features and physicochemical properties were extensively characterized via XRD patterns, SEM/TEM images, TGA profiles, FT-IR and UV-Vis spectra. In particular, their fractal features, the pair distance distribution function, and the Porod plots were evaluated thoroughly on the basis of the SAXS data. Meanwhile, their catalytic performances for asymmetric aldol reactions between p-nitrobenzaldehyde and cyclohexanone were evaluated. The results indicated that the bimodal mesoporous BMMs-based samples with short worm-like mesoporous channels possessed both mass and surface fractal features, whereas the MCM-41- and SBA-15-based samples with long-range ordered structures only showed surface fractal features. The influences of various reaction parameters, including the textures of the mesoporous silicas, the structures of the used chiral ligands, and the molecular volumes of aldehydes, on the catalytic activities (yield) and stereoselectivities (dr and ee) were investigated thoroughly. The results showed satisfactory activities (yields) and better stereoselectivity (dr and ee) in comparison with the homogeneous catalytic system using Z as the catalysts. In particular, the 3rd recycle catalytic performances of the Z-immobilized heterogeneous catalysts retained high catalytic yields (around 80%) and ee values of 28%. These phenomena were well interpreted by the essential relationships between the fractal characteristics of these heterogeneous catalysts and their catalytic activities. The relationships between the fractal evolution and catalytic behavior of the resultant catalysts were deeply explored via SAXS method and other characterizations. The applicability and reliability of fractal theory are therefore proved.
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影响因子：
5.4
作者：
Calderón, F;Fernández, R;Fernández-Mayoralas, A
通讯作者：
Fernández-Mayoralas, A
影响因子：
2.1
作者：
Dulger, Habibe;Sari, Ozlem;Erdem, Safiye S.
通讯作者：
Erdem, Safiye S.
影响因子：
4.4
作者：
AVNIR, D;FARIN, D;PFEIFER, P
通讯作者：
PFEIFER, P
影响因子：
4.2
作者：
Khorasheh, F;Radmanesh, R;Kazemeini, M
通讯作者：
Kazemeini, M
影响因子：
2.1
作者：
Prause, Felix;Wagner, Stefan;Breuning, Matthias
通讯作者：
Breuning, Matthias