Department of Materials Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan.
Nat Chem. 2015 Nov;7(11):905-12. doi: 10.1038/nchem.2352. Epub 2015 Sep 21.
The periodic layers and ordered nanochannels of covalent organic frameworks (COFs) make these materials viable open catalytic nanoreactors, but their low stability has precluded their practical implementation. Here we report the synthesis of a crystalline porous COF that is stable against water, strong acids and strong bases, and we demonstrate its utility as a material platform for structural design and functional development. We endowed a crystalline and porous imine-based COF with stability by incorporating methoxy groups into its pore walls to reinforce interlayer interactions. We subsequently converted the resulting achiral material into two distinct chiral organocatalysts, with the high crystallinity and porosity retained, by appending chiral centres and catalytically active sites on its channel walls. The COFs thus prepared combine catalytic activity, enantioselectivity and recyclability, which are attractive in heterogeneous organocatalysis, and were shown to promote asymmetric C-C bond formation in water under ambient conditions.
共价有机框架（COFs）的周期性层和有序纳米通道使这些材料成为可行的开放式催化纳米反应器，但它们的低稳定性限制了其实际应用。在这里，我们报告了一种稳定的水、强酸和强碱的结晶多孔 COF 的合成，并证明了它作为结构设计和功能开发的材料平台的实用性。我们通过在孔壁中引入甲氧基来增强层间相互作用，从而使结晶多孔亚胺基 COF 具有稳定性。随后，我们通过在通道壁上附加手性中心和催化活性位点，将所得的非手性材料转化为两种不同的手性有机催化剂，同时保持高结晶度和孔隙率。所制备的 COFs 结合了在非均相有机催化中具有吸引力的催化活性、对映选择性和可回收性，并在环境条件下促进了水中不对称 C-C 键的形成。
