Syntheses, crystal structures and adsorption properties of ultramicroporous coordination polymers constructed from hexafluorosilicate ions and pyrazine

Abstract

The cover picture The cover picture shows two crystal structures of porous coordination polymers, [Cu(SiF₆)(4,4′bpy)₂]_n and [Zn(SiF₆)(pyz)₂]_n (4,4′‐bpy = 4,4′‐bipyridine, pyz = pyrazine), which have been generated from square‐grid coordination polymers that are cross‐linked by ν‐SiF₆ anions. Although typical bridging ligands such as 4,4′‐bpy and 1,4‐benzenedicarboxylate produce open octahedral coordination polymers with micropores, such micropores need to be further narrowed to become ultramicropores (< 7 Å) for separation and purification of smaller gas molecules. We have succeeded in obtaining the ultramicroporous coordination polymer [Zn(SiF₆)(pyz) ₂]_n with 4.5 ± 4.5 Ų pores by simply replacing 4,4′‐bpy in [M(SiF₆)(4,4′‐bpy)₂] _n (M = Zn²⁺, Cu²⁺) with pyz. The ultramicropores of [Zn(SiF₆)(pyz)₂]_n adsorb Me₂CO rather than iPrOH, showing the size‐exclusive effect. Additionally this compound shows a sharp uptake in H₂ adsorption at 77 K, because the interaction potential is expected to be strong as a result of the synergistic effect of the neighbouring pore walls. Details are discussed in the article by K. Uemura et al. on p. 2329 ff.