Equipe Matériaux à Porosité Controlée (MPC), Institut de Science des Matériaux de Mulhouse (IS2M), LRC CNRS-UHA 7228, ENSCMu, 3 rue Alfred Werner, 68093 Mulhouse Cedex, France.
J Am Chem Soc. 2012 May 16;134(19):8115-26. doi: 10.1021/ja211864w. Epub 2012 Mar 20.
The objective of this work was to study the adsorption and separation of the most important families of hydrocarbon compounds on metal-organic frameworks (MOFs), in comparison with zeolites. For this purpose, we have selected four probe molecules, each of them representing one of these families, i.e., o- and p-xylene as aromatics, 1-octene as an alkene, and n-octane as an alkane. The separation of these four molecules was studied by binary breakthrough experiments. To represent the large diversity of MOF structures, the experiments were carried out with (i) two MOFs with coordinatively unsaturated metal sites (CUS), i.e., Cu-btc (HKUST-1) and CPO-27-Ni, (ii) a MOF with an anionic framework and extraframework cations, i.e. RHO-ZMOF, and (iii) two rather apolar zeolitic imidazolate framework (ZIF) materials with different pore sizes, i.e. ZIF-8 and ZIF-76. Zeolite NaY and zeolite β were used as polar and apolar reference adsorbents, respectively. The results can be briefly summarized as follows: ZIFs (not carrying any polar functional groups) behave like apolar adsorbents and exhibit very interesting and unexpected molecular sieving properties. CUS-MOFs behave like polar adsorbents but show the specificity of preferring alkenes over aromatics. This feature is rationalized thanks to DFT+D calculations. MOFs with extraframework cations behave like polar (cationic) zeolites.
这项工作的目的是研究金属有机骨架（MOFs）对最重要的烃类化合物族的吸附和分离，与沸石进行比较。为此，我们选择了四种探针分子，它们分别代表这些族中的一种，即邻二甲苯和对二甲苯作为芳烃、1-辛烯作为烯烃和正辛烷作为烷烃。通过二元穿透实验研究了这些四种分子的分离。为了表示 MOF 结构的多样性，实验采用了（i）两种具有配位不饱和金属位的 MOF，即 Cu-btc（HKUST-1）和 CPO-27-Ni，（ii）一种具有阴离子骨架和外骨架阳离子的 MOF，即 RHO-ZMOF，以及（iii）两种具有不同孔径的相当非极性沸石咪唑骨架（ZIF）材料，即 ZIF-8 和 ZIF-76。沸石 NaY 和沸石β分别用作极性和非极性参考吸附剂。结果可以简要概括如下：ZIFs（不携带任何极性官能团）表现出非极性吸附剂的性质，并表现出非常有趣和意想不到的分子筛性质。CUS-MOFs 表现出极性吸附剂的性质，但显示出优先选择烯烃而不是芳烃的特异性。这一特征通过 DFT+D 计算得到了合理化。具有外骨架阳离子的 MOFs 表现出类似于极性（阳离子）沸石的性质。
