Two Zinc(II) Coordination Polymers Constructed with Rigid 1,4-Benzenedicarboxylate and Flexible 1,4-Bis(imidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene Linkers: From Interpenetrating Layers to Templated 3D Frameworks

Two new coordination polymers, [Zn(bdc)(bimx)]·1.5H<sub>2</sub>O (<b>1</b>) and [Zn<sub>2</sub>(bdc)<sub>2</sub>(bimx)]·(H<sub>2</sub>bdc) (<b>2</b>) (H<sub>2</sub>bdc = 1,4-benzenedicarboxylic acid, bimx = 1,4-bis(imidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene), containing both rigid (bdc) and flexible (bimx) linkers were synthesized in aqueous media (hydrothermal conditions) and characterized by single-crystal and powder X-ray diffraction, FT-IR spectroscopy, and thermogravimetric/differential thermal analysis. While <b>1</b> is an essentially dense material consisting of stacked composite layers each being built from two mutually interpenetrating two-dimensional square-grid frameworks, <b>2</b> possesses a single (non-interpenetrated) three-dimensional open framework (α-Po net) with wide channels that are filled with H<sub>2</sub>bdc template molecules. Formally, ring-penetrating bdc linkers are replaced by H<sub>2</sub>bdc molecules when going from the structure of <b>1</b> to the structure of <b>2</b>. The occluded H<sub>2</sub>bdc molecules exhibit distinct interactions with the framework and can thus be regarded as template molecules or structure-directing agents. In line with these host−guest interactions, attempts to remove the template from as-synthesized <b>2</b> with retention of the framework structure by heat treatment or liquid exchange were not successful. These results give new impetus, however, to the recently discussed idea to use structure-directing effects, as they occur in zeolite synthesis, for the preparation of metal−organic framework materials.