A structurally stable 3D supramolecular framework with 4.0% guest-accessible void spaces that are reversibly occupied by guest water molecules

A new Cd(II)-Cu(II)-containing coordination compound, namely Cu(bpy)Cd(ip)2(μ-OH2) · (H2O)2 (1, bpy = 2,2′-bipyridine, H2ip = m-phthalic acid), has been synthesized hydrothermally by the reaction of CdCl2, CuCl2, bpy, and H2ip. In 1, Cd(II) and Cu(II) ions are in turn connected by ip2− ligands to generate the 2D (4, 4) nets. Further, these 2D sheets are linked together via π-π, C-H…O, and O-H…O contacts, thus resulting in the 3D supramolecular frameworks with the irregular 1D channels occupied by water molecules. Remarkably, the investigation by using IR, TG, and PXRD (powder X-ray diffraction) shows that the uptake and release of guest water molecules will not influence the structural integrity.