Rational Design and Synthesis of Porous Organic−Inorganic Hybrid Frameworks Constructed by 1,3,5-Benzenetriphosphonic Acid and Pyridine Synthons

1,3,5-Benzenetriphosphonic acid, H₆BTP, 1,3,5-[(HO)₂OP]₃C₆H₃, was reacted hydrothermally with copper salts in the absence and presence of 4,4‘-bipyridine (bpy) and 4,4‘-trimethlyenedipyridine (tbpy) in a 1:1 molar ratio leading to three new organic−inorganic hybrid frameworks. Compound 1, {Cu₆[C₆H₃(PO₃)₃]₂(H₂O)₈}·5.5H₂O, has three different copper ions that are interconnected by the highly charged [1,3,5-(PO₃)₃C₆H₃]^6- anionic moieties. These moieties self-assemble through tetra-copper units to give a cagelike motif with two benzene rings parallel to each other at a distance of 3.531 Å which extend along the a axis and link with a grouping of four-coordinated copper units in the b axis direction to give the cross-linked layered structure. In compound 2, Cu{C₆H₃[PO(OH)O]₂[PO(OH)₂]}(C₁₀H₈N₂), the copper ions are in square pyramidal geometries and are interconnected via chelating and bridging BTP ligands into layers which are further cross-linked by bpy ligands into a pillared layered architecture. Compound 3, {Cu₂C₆H₃[PO(OH)O]₂[PO₃](C₁₃H₁₄N₂)}·3H₂O·0.5HCON(CH₃)₂, contains tetra-copper units that are linked by BTP ligands and further linked by tbpy linkers in the c axis direction to produce a large channel-sized 3D framework.