Enge Kanäle mit polaren Wänden bestimmen Struktur und Funktion eines Metall‐organischen Gerüsts aus Zinkionen und einem Imidazolat‐Amid‐Imidat‐Liganden (siehe Struktur: Zn orange, N blau, O rot, C dunkelgrau, H hellgrau), das über eine hohe Aufnahmekapazität für H2 und CO2 verfügt. Der starre und stabile Chelatligand entsteht in situ durch partielle Hydrolyse eines Dicyanimidazols.

We report on a new series of isoreticular frameworks based on zinc and 2‐substituted imidazolate‐4‐amide‐5‐imidate (IFP‐1–4, IFP=imidazolate framework Potsdam) that form one‐dimensional, microporous hexagonal channels. Varying R in the 2‐substitued linker (R=Me (IFP‐1), Cl (IFP‐2), Br (IFP‐3), Et (IFP‐4)) allowed the channel diameter (4.0–1.7 Å), the polarisability and functionality of the channel walls to be tuned. Frameworks IFP‐2, IFP‐3 and IFP‐4 are isostructural to previously reported IFP‐1. The structures of IFP‐2 and IFP‐3 were solved by X‐ray crystallographic analyses. The structure of IFP‐4 was determined by a combination of PXRD and structure modelling and was confirmed by IR spectroscopy and 1H MAS and 13C CP‐MAS NMR spectroscopy. All IFPs showed high thermal stability (345–400 °C); IFP‐1 and IFP‐4 were stable in boiling water for 7 d. A detailed porosity analysis was performed on the basis of adsorption measurements by using various gases. The potential of the materials to undergo specific interactions with CO2 was investigated by measuring the isosteric heats of adsorption. The capacity to adsorb CH4 (at 298 K), CO2 (at 298 K) and H2 (at 77 K) at high pressure were also investigated. In situ IR spectroscopy showed that CO2 is physisorbed on IFP‐1–4 under dry conditions and that both CO2 and H2O are physisorbed on IFP‐1 under moist conditions.

Narrow channels with polar walls are the structural and functional features responsible for the high capacity of a zinc–organic framework based on an imidazolate–amide–imidate ligand for the uptake of H2 and CO2 (see structure: orange Zn, blue N, red O, dark gray C, light gray H). The rigid and stable chelating ligand was synthesized in situ by partial hydrolysis of a dicyanoimidazole compound.

In this work the adsorption of CO 2 and CH 4 on a series of isoreticular microporous metal-organic frameworks based on 2-substituted imidazolate-4-amide-5-imidates, IFP-1-IFP-6 (IFP ¼ Imidazolate Framework Potsdam), is studied firstly by pure gas adsorption at 273 K. All experimental isotherms can be nicely described by using the Toth isotherm model and show the preferred adsorption of CO 2 over CH 4 . At low pressures the Toth isotherm equation exhibits a Henry region, wherefore Henry's law constants for CO 2 and CH 4 uptake could be determined and ideal selectivity a CO 2 /CH 4 has been calculated. Secondly, selectivities were calculated from mixture data by using nearly equimolar binary mixtures of both gases by a volumetric-chromatographic method to examine the IFPs. Results showed the reliability of the selectivity calculation. Values of a CO 2 /CH 4 around 7.5 for IFP-5 indicate that this material shows much better selectivities than IFP-1, IFP-2, IFP-3, IFP-4 and IFP-6 with slightly lower selectivity a CO 2 /CH 4 ¼ 4-6. The preferred adsorption of CO 2 over CH 4 especially of IFP-5 and IFP-4 makes these materials suitable for gas separation application.