Department of Chemistry, University of California-Berkeley, CA 94720, USA.
Science. 2013 May 24;340(6135):960-4. doi: 10.1126/science.1234071.
Metal-organic frameworks can offer pore geometries that are not available in zeolites or other porous media, facilitating distinct types of shape-based molecular separations. Here, we report Fe2(BDP)3 (BDP(2-) = 1,4-benzenedipyrazolate), a highly stable framework with triangular channels that effect the separation of hexane isomers according to the degree of branching. Consistent with the varying abilities of the isomers to wedge along the triangular corners of the structure, adsorption isotherms and calculated isosteric heats indicate an adsorption selectivity order of n-hexane > 2-methylpentane > 3-methylpentane > 2,3-dimethylbutane ≈ 2,2-dimethylbutane. A breakthrough experiment performed at 160°C with an equimolar mixture of all five molecules confirms that the dibranched isomers elute first from a bed packed with Fe2(BDP)3, followed by the monobranched isomers and finally linear n-hexane. Configurational-bias Monte Carlo simulations confirm the origins of the molecular separation.
金属有机骨架可以提供沸石或其他多孔介质中无法获得的孔几何形状，从而促进基于形状的不同类型的分子分离。在这里，我们报告了 Fe2(BDP)3（BDP(2-) = 1,4-苯二吡唑），这是一种具有三角形通道的高度稳定的骨架，可以根据支化程度分离正己烷异构体。与异构体沿着结构的三角形顶角楔入的能力变化一致，吸附等温线和计算的等焓表明吸附选择性顺序为 n-己烷>2-甲基戊烷>3-甲基戊烷>2,3-二甲基丁烷≈2,2-二甲基丁烷。在 160°C 下用所有五个分子的等摩尔混合物进行的突破实验证实，二支化异构体首先从填充有 Fe2(BDP)3 的床层中洗脱出来，其次是单支化异构体，最后是线性 n-己烷。构象偏差蒙特卡罗模拟证实了分子分离的起源。
