Loading‐Dependent Transport Properties of Zeolitic Imidazolate Frameworks Probed by In‐Situ PFG NMR

Zeolitic imidazolate frameworks (ZIFs), a unique subclass of metal‐organic frameworks (MOFs) recently reported by Yaghi group and others, are attracting worldwide attention. Our systematic work on the adsorption and molecular transport in ZIFs has revealed some unique properties of these new materials that could not have been anticipated from standard structural characterization results. More specifically, the rearrangement of the imidazolate linkers (and in some cases, the framework structure) driven by adsorbate‐adsorbent interaction causes the window sizes and accessible pore space of ZIFs to deviate (in some cases, drastically) from the values determined by low‐temperature single‐crystal X‐ray crystallography and typical physisorption experiments carried out at liquid nitrogen temperature (77 K) with H2, N2 and Ar. Here we show the high degree of structural flexibility of ZIFs at near ambient temperatures and report the first time their unique adsorption and transport characteristics.