Flexible covalent-organic frameworks (COFs) display a variety of guest-dependent dynamic behaviors, but because these are an emerging class of materials, very little experimental adsorption data exists. This work examines the adsorption properties of COF-506 and COF-506-Cu utilizing various adsorbates as probe molecules. These materials have small surface areas (<100 m²/g) but still have significant capacity for methanol and isopropanol compared to activated carbon, even though the COF contains approximately 1/10th the surface area of many activated carbons. Isotherms for ethane/ethylene collected up to 1 bar show moderate selectivity for ethylene, but interestingly, this selectivity is reversed when the isotherms are measured up to 5 bar. The change in selectivity occurs because the ethane isotherm has a distinct stepwise increase in capacity near 4 bar. The adsorption data indicate broad generalizations and analogies of COFs to activated carbon should be avoided; that the adsorption capacity COFs may not correlate to surface area; and that high-pressure adsorption isotherms may have steps in the adsorption isotherm where capacity increases significantly.

中文翻译：

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柔性 COF-506 和 COF-506-Cu 中的气体吸附


柔性共价有机框架 （COF） 表现出各种依赖于客体的动态行为，但由于这些是一类新兴材料，因此存在很少的实验吸附数据。本工作利用各种吸附物作为探针分子研究了 COF-506 和 COF-506-Cu 的吸附特性。这些材料的表面积很小（<100 m²/g），但与活性炭相比，它们仍然具有很大的甲醇和异丙醇容量，即使COF的表面积约为许多活性炭的1/10。在高达 1 bar 的压力下收集的乙烷/乙烯的等温线对乙烯显示出中等选择性，但有趣的是，当等温线测量高达 5 bar 时，这种选择性是相反的。选择性发生变化是因为乙烷等温线在 4 bar 附近具有明显的逐步增加容量。吸附数据表明，应避免将 COF 与活性炭进行广泛的概括和类比;吸附能力 COF 可能与表面积无关;并且高压吸附等温线可能在吸附等温线中具有容量显著增加的台阶。