Greenaway Rebecca L, Holden Daniel, Eden Edward G B, Stephenson Andrew, Yong Chin W, Bennison Michael J, Hasell Tom, Briggs Michael E, James Stuart L, Cooper Andrew I
Department of Chemistry and Materials Innovation Factory , University of Liverpool , Crown Street , Liverpool , L69 7ZD , UK . Email:
Scientific Computing Department , Science and Technologies Facilities Council , Daresbury Laboratory , Sci-Tech Daresbury , Warrington , WA4 4AD , UK.
Chem Sci. 2017 Apr 1;8(4):2640-2651. doi: 10.1039/c6sc05196k. Epub 2017 Jan 31.
Porous liquids are a new class of material that could have applications in areas such as gas separation and homogeneous catalysis. Here we use a combination of measurement techniques, molecular simulations, and control experiments to advance the quantitative understanding of these liquids. In particular, we show that the cage cavities remain unoccupied in the absence of a suitable guest, and that the liquids can adsorb large quantities of gas, with gas occupancy in the cages as high as 72% and 74% for Xe and SF, respectively. Gases can be reversibly loaded and released by using non-chemical triggers such as sonication, suggesting potential for gas separation schemes. Diffusion NMR experiments show that gases are in dynamic equilibrium between a bound and unbound state in the cage cavities, in agreement with recent simulations for related porous liquids. Comparison with gas adsorption in porous organic cage solids suggests that porous liquids have similar gas binding affinities, and that the physical properties of the cage molecule are translated into the liquid state. By contrast, some physical properties are different: for example, solid homochiral porous cages show enantioselectivity for chiral aromatic alcohols, whereas the equivalent homochiral porous liquids do not. This can be attributed to a loss of supramolecular organisation in the isotropic porous liquid.
多孔液体是一类新型材料，可应用于气体分离和均相催化等领域。在此，我们结合测量技术、分子模拟和对照实验，以深化对这些液体的定量认识。具体而言，我们发现，在没有合适客体的情况下，笼腔为空，且这些液体能够吸附大量气体，对于氙气和六氟化硫，笼中的气体占有率分别高达72%和74%。通过使用超声处理等非化学触发手段，气体能够可逆地加载和释放，这表明其在气体分离方案方面具有潜力。扩散核磁共振实验表明，气体在笼腔中的束缚态和非束缚态之间处于动态平衡，这与近期对相关多孔液体的模拟结果一致。与多孔有机笼状固体中的气体吸附情况相比，多孔液体具有相似的气体结合亲和力，且笼状分子的物理性质转化到了液态中。相比之下，一些物理性质有所不同：例如，固态同手性多孔笼对手性芳香醇表现出对映选择性，而等效的同手性多孔液体则没有。这可归因于各向同性多孔液体中分子超结构的丧失。
