Energy-efficient approaches to propylene/propane separation such as molecular sieving are of considerable importance for the petrochemical industry. The metal organic framework NbOFFIVE-1-Ni adsorbs propylene but not propane at room temperature and atmospheric pressure, whereas the isostructural SIFSIX-3-Ni does not exclude propane under the same conditions. The static dimensions of the pore openings of both materials are too small to admit either guest, signalling the importance of host dynamics for guest entrance to and transport through the channels. We use ab initio calculations together with crystallographic and adsorption data to show that the dynamics of the two framework-forming units, polyatomic anions and pyrazines, govern both diffusion and separation. The guest diffusion occurs by opening of the flexible window formed by four pyrazines. In NbOFFIVE-1-Ni, (NbOF₅)²⁻ anion reorientation locates propane away from the window, which enhances propylene/propane separation.

高效节能的丙烯/丙烷分离方法（例如分子筛）对于石化行业至关重要。金属有机骨架NbOFFIVE -1-Ni在室温和大气压下吸附丙烯，但不吸附丙烷，而同构SIFSIX-3-Ni在相同条件下不排除丙烷。两种材料的孔隙开口的静态尺寸都太小，以至于不允许任何一种客体进入，这表明宿主动力学对于客体进入和通过通道运输的重要性。我们使用从头算以及晶体学和吸附数据来表明两个骨架形成单元（多原子阴离子和吡嗪）的动力学决定着扩散和分离。通过打开由四个吡嗪形成的柔性窗而发生客体扩散。在NbOFFIVE -1-Ni中，（NbOF ₅）^2-阴离子的重新定位使丙烷远离窗口，从而增强了丙烯/丙烷的分离。