Liquids with permanent porosity
Liquids with permanent porosity
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DOI：
10.1038/nature16072
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发表时间：
2015-11-12
期刊：
影响因子：
64.8
通讯作者：
James, Stuart L.
中科院分区：
文献类型：
--
作者：
Giri, Nicola;Del Popolo, Mario G.;James, Stuart L.
分子筛(1)和金属有机骨架(2，3)等多孔固体在分子分离和催化中是有用的，但它们的固体性质可能会造成限制。例如，液体溶剂，而不是多孔固体，是燃烧后捕获二氧化碳最成熟的技术，因为液体循环系统更容易改装到现有工厂。固体多孔吸附剂具有主要的优点，例如在吸附-解吸循环中降低能量损失(4)，但它们在传统的流动过程中很难实现。因此，结合了流动性和永久多孔性的材料可以提供技术优势，但永久多孔性与传统液体不相关。在这里，我们报告了自由流动的液体，其体积特性由其永久孔隙率决定。为了实现这一点，我们设计了笼形分子(6，7)，这些分子提供了一个明确的孔隙空间，并且在分子太大而无法进入孔隙的溶剂中高度溶解。因此，空笼的浓度可能比其他含有空穴(8-10个)的分子溶液的浓度高约500倍，从而导致整体性质的显著变化，例如甲烷气体的溶解度增加了8倍。我们的结果为开发一种用于化学过程的新型功能性多孔材料提供了基础，我们提出了一种一步、多克放大路线，用于从商业可获得的试剂混合物中制备高度可溶的“混杂”多孔笼。这些材料的统一设计原则是避免官能团渗透到分子笼腔中。
Porous solids such as zeolites(1) and metal-organic frameworks(2,3) are useful in molecular separation and in catalysis, but their solid nature can impose limitations. For example, liquid solvents, rather than porous solids, are the most mature technology for post-combustion capture of carbon dioxide because liquid circulation systems are more easily retrofitted to existing plants. Solid porous adsorbents offer major benefits, such as lower energy penalties in adsorption-desorption cycles(4), but they are difficult to implement in conventional flow processes. Materials that combine the properties of fluidity and permanent porosity could therefore offer technological advantages, but permanent porosity is not associated with conventional liquids(5). Here we report free-flowing liquids whose bulk properties are determined by their permanent porosity. To achieve this, we designed cage molecules(6,7) that provide a well-defined pore space and that are highly soluble in solvents whose molecules are too large to enter the pores. The concentration of unoccupied cages can thus be around 500 times greater than in other molecular solutions that contain cavities(8-10), resulting in a marked change in bulk properties, such as an eightfold increase in the solubility of methane gas. Our results provide the basis for development of a new class of functional porous materials for chemical processes, and we present a one-step, multigram scale-up route for highly soluble 'scrambled' porous cages prepared from a mixture of commercially available reagents. The unifying design principle for these materials is the avoidance of functional groups that can penetrate into the molecular cage cavities.