Klein Ryan A, Bingel Lukas W, Halder Arijit, Carter Marcus, Trump Benjamin A, Bloch Eric D, Zhou Wei, Walton Krista S, Brown Craig M, McGuirk C Michael
Materials, Chemical, and Computational Sciences, National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
J Am Chem Soc. 2023 Oct 11;145(40):21955-21965. doi: 10.1021/jacs.3c06754. Epub 2023 Sep 29.
A proposed low-energy alternative to the separation of alkanes from alkenes by energy-intensive cryogenic distillation is separation by porous adsorbents. Unfortunately, most adsorbents preferentially take up the desired, high-value major component alkene, requiring frequent regeneration. Adsorbents with inverse selectivity for the minor component alkane would enable the direct production of purified, reagent-grade alkene, greatly reducing global energy consumption. However, such materials are exceedingly rare, especially for propane/propylene separation. Here, we report that through adaptive and spontaneous pore size and shape adaptation to optimize an ensemble of weak noncovalent interactions, the structurally responsive metal-organic framework CdIF-13 (-Cd(benzimidazolate)) exhibits inverse selectivity for propane over propylene with record-setting separation performance under industrially relevant temperature, pressure, and mixture conditions. Powder synchrotron X-ray diffraction measurements combined with first-principles calculations yield atomic-scale insight and reveal the induced fit mechanism of adsorbate-specific pore adaptation and ensemble interactions between ligands and adsorbates. Dynamic column breakthrough measurements confirm that CdIF-13 displays selectivity under mixed-component conditions of varying ratios, with a record measured selectivity factor of α ≈ 3 at 95:5 propylene:propane at 298 K and 1 bar. When sequenced with a low-cost rigid adsorbent, we demonstrated the direct purification of propylene under ambient conditions. This combined atomic-level structural characterization and performance testing firmly establishes how cooperatively flexible materials can be capable of unprecedented separation factors.
一种替代通过高能耗低温蒸馏从烯烃中分离烷烃的低能耗方法是使用多孔吸附剂进行分离。不幸的是，大多数吸附剂优先吸附所需的高价值主要成分烯烃，这需要频繁再生。对次要成分烷烃具有反向选择性的吸附剂能够直接生产纯化的试剂级烯烃，从而大大降低全球能源消耗。然而，这类材料极为罕见，尤其是用于丙烷/丙烯分离的材料。在此，我们报告称，通过适应性和自发性的孔径和形状适配来优化一系列弱非共价相互作用，结构响应性金属有机框架CdIF-13（-Cd(苯并咪唑)）在工业相关的温度、压力和混合条件下，对丙烷的选择性高于丙烯，具有创纪录的分离性能。粉末同步加速器X射线衍射测量结合第一性原理计算提供了原子尺度的见解，并揭示了吸附质特异性孔适配以及配体与吸附质之间整体相互作用的诱导契合机制。动态柱穿透测量证实，CdIF-13在不同比例的混合组分条件下表现出选择性，在298 K和1 bar下，在丙烯:丙烷为95:5时，测得的选择性因子α≈3，创历史记录。当与低成本刚性吸附剂串联使用时，我们展示了在环境条件下直接纯化丙烯的过程。这种结合原子水平结构表征和性能测试的方法，牢固地确立了协同柔性材料如何能够实现前所未有的分离因子。
