Discrimination of Small Gas Molecules through Adsorption: Reverse Selectivity for Hydrogen in a Flexible Metal−Organic Framework
2009-11-02T00:00:00Z (GMT) by
Zn<sup>2+</sup> ions react with 3,5-pyridinedicarboxylate (pydc) to form a new metal−organic framework (MOF), [Zn(pydc)(dma)] (dma = <i>N</i>,<i>N</i>′-dimethylacetamide), based on a noninterpenetrating (10,3)-<i>a</i> 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 H<sub>2</sub> at 77 K, which is very unusual in MOFs. At 195 K, only CO<sub>2</sub> is selectively adsorbed by this material because of the temperature dependence of the gated adsorption.