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.