Enhancing chemical reactions in a confined hydrophobic environment: an NMR study of benzene hydroxylation in carbon nanotubes
Enhancing chemical reactions in a confined hydrophobic environment: an NMR study of benzene hydroxylation in carbon nanotubes
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DOI：
10.1039/c2sc21761a
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发表时间：
2013-02
期刊：
影响因子：
8.4
通讯作者：
Hongbo Zhang;Xiulian Pan;Xiuwen Han;Xiumei Liu;Xuefeng Wang;W. Shen;X. Bao
中科院分区：
文献类型：
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作者：
Hongbo Zhang;Xiulian Pan;Xiuwen Han;Xiumei Liu;Xuefeng Wang;W. Shen;X. Bao
我们在这里展示了一个概念，即化学反应可以通过利用碳纳米管（CNT）通道的受限疏水环境来增强，从而在反应过程中将产物与反应物分离，从而改变反应平衡。以苯羟基化为苯酚为例，我们观察到，固体核磁共振研究表明，苯在碳纳米管通道内富集，而产物苯酚被区分性地排出通道外。因此，在碳纳米管约束的Re催化剂上的反应活性比分散在相同碳纳米管外壁上的相同催化剂高4倍。通过在商业活性炭负载催化剂上改变反应中苯的用量，进一步证实了苯的选择性富集对反应的影响。碳纳米管通道区分疏水分子和亲水分子被认为是一个普遍的特征。这对许多涉及不同疏水性分子的有机合成过程具有重要意义。
We demonstrate here a concept that chemical reactions can be enhanced by utilizing the confined hydrophobic environment of carbon nanotube (CNT) channels to separate products from reactants during a reaction and hence shift the reaction equilibrium. Taking the hydroxylation of benzene to phenol as an example, we observed that benzene is enriched inside CNT channels while the product phenol was discriminatively expelled out of the channels, as shown by solid state NMR studies. Consequently, the reaction over a CNT-confined Re catalyst exhibited a 4 times higher activity than the same catalyst dispersed on the outer walls of the same CNTs. The effect of this selective enrichment of benzene on the reaction was further confirmed by varying the amount of benzene in the reaction over commercial activated carbon-supported catalyst. CNT channels discriminating hydrophobic from hydrophilic molecules are expected to be a general feature. It is of significance for many synthetic organic processes involving molecules with different hydrophobicity in the reactants and products.