Discrimination of Small Gas Molecules through Adsorption: Reverse Selectivity for Hydrogen in a Flexible Metal−Organic Framework

Zn2+ ions react with 3,5-pyridinedicarboxylate (pydc) to form a new metal−organic framework (MOF), [Zn(pydc)(dma)] (dma = N,N′-dimethylacetamide), based on a noninterpenetrating (10,3)-a topology. The framework possessing narrow one-dimensional channels is highly flexible, and as a result, guest-dependent breakthrough-like adsorptions occur under atmospheric pressure. This “gate opening” requires strong interactions between gas molecules and the adsorbent, and therefore [Zn(pydc)(dma)] shows a reverse selectivity for H2 at 77 K, which is very unusual in MOFs. At 195 K, only CO2 is selectively adsorbed by this material because of the temperature dependence of the gated adsorption.

Zn2+ 离子与 3,5-吡啶二羧酸（pydc）反应，形成一种新型的金属-有机框架（MOF），[Zn(pydc)(dma)]（其中 dma 代表 N,N'-二甲基乙酰胺），该框架基于非交叉式（10,3）拓扑结构。该框架具有狭窄的一维通道，表现出极高的灵活性，因此在大气压力下，发生依赖于客体分子的突破性吸附。这种‘门控开启’过程需要气体分子与吸附剂之间强烈的相互作用，因此 [Zn(pydc)(dma)] 在 77 K 下对 H2 表现出反向选择性，这在 MOFs 中颇为罕见。在 195 K 时，由于门控吸附的温度依赖性，该材料仅对 CO2 进行选择性吸附。