Department of Chemistry, CB#3290, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Nat Chem. 2010 Oct;2(10):838-46. doi: 10.1038/nchem.738. Epub 2010 Jul 25.
Metal-organic frameworks, built by bridging metal ions with organic linkers, represent a new class of porous hybrid materials with attractive tunability in compositions, structures and functions. In particular, the mild conditions typically employed for their synthesis allow for the functionalization of their building blocks, and thus the rational design of novel materials. Here we demonstrate the systematic design of eight mesoporous chiral metal-organic frameworks, with the framework formula [LCu2(solvent)2] (where L is a chiral tetracarboxylate ligand derived from 1,1'-bi-2-naphthol), that have the same structures but channels of different sizes. Chiral Lewis acid catalysts were generated by postsynthesis functionalization with Ti(OiPr)4, and the resulting materials proved to be highly active asymmetric catalysts for diethylzinc and alkynylzinc additions, which converted aromatic aldehydes into chiral secondary alcohols. The enantioselectivities of these reactions can be modified by tuning the size of the channels, which alters the diffusion rates of the organic substrates.
金属-有机骨架由金属离子与有机连接体桥接而成，代表了一类具有吸引力的多孔杂化材料，其组成、结构和功能具有可调节性。特别是，它们的合成通常采用温和的条件，允许对其构建块进行功能化，从而可以合理设计新型材料。在这里，我们展示了八种介孔手性金属-有机骨架的系统设计，其骨架公式为[LCu2（溶剂）2]（其中 L 是由 1,1'-联萘-2-酚衍生而来的手性四羧酸配体），这些骨架具有相同的结构，但通道大小不同。通过后合成功能化用 Ti(OiPr)4 生成手性路易斯酸催化剂，所得材料被证明是二乙基锌和炔基锌加成反应的高效不对称催化剂，可将芳香醛转化为手性仲醇。这些反应的对映选择性可以通过调节通道的大小来改变，从而改变有机底物的扩散速率。
