The role of the support properties in the catalytic performance of an anchored copper(<scp>ii</scp>) aza-bis(oxazoline) in mesoporous silicas and their carbon replicas
作者:Ana Rosa Silva、Vanessa Guimarães、Ana Paula Carvalho、João Pires
DOI:10.1039/c2cy20638b
日期:——
A copper(II) chiral aza-bis(oxazoline) catalyst (CuazaBox) was anchored onto ordered mesoporous silicas and their carbon replicas. The materials were characterized by elemental analysis (C, N, H, S), ICP-AES, FTIR, XPS, thermogravimetry and isotherms of N2 adsorption at −196 °C. The materials were tested as heterogeneous catalysts in the reaction of cyclopropanation of styrene to check the effect of porous material type on the catalytic parameters, as well as on their reutilization. Generally, the composites were more active and enantioselective in the cyclopropanation of styrene than the corresponding homogeneous phase reaction run under similar experimental conditions. The materials pHpzc proved to be an important factor not only in the CuazaBox anchoring yields, but also in their catalytic performance. Less acidic surfaces (SPSi and CMK-3) yielded heterogeneous catalysts with higher styrene conversion and enantioselectivity. The materials could also be recycled with comparable enantioselectivities or generally a slight decrease in the enantioselectivity.
一种铜(II)手性偶氮双(噁唑啉)催化剂(CuazaBox)被锚定在有序介孔硅及其碳复制品上。通过元素分析(C、N、H、S)、ICP-AES、傅立叶变换红外光谱、XPS、热重分析以及 -196 °C 下的 N2 吸附等温线对这些材料进行了表征。在苯乙烯的环丙烷化反应中将这些材料作为异相催化剂进行了测试,以检验多孔材料类型对催化参数的影响以及对其再利用的影响。一般来说,在类似的实验条件下,复合材料在苯乙烯的环丙烷化反应中比相应的均相反应具有更高的活性和对映选择性。事实证明,材料的 pHpzc 不仅是影响 CuazaBox 锚定产量的重要因素,也是影响其催化性能的重要因素。酸性较低的表面(SPSi 和 CMK-3)产生的异相催化剂具有更高的苯乙烯转化率和对映体选择性。这些材料还可以在对映体选择性相当或对映体选择性略有降低的情况下进行回收利用。