Metal-organic hybrid supramolecular architectures based on lighter transition metal ions are anemerging class of ferroelectric materials due to their highly crystalline nature and less toxicity. However,synthesizing polar metal-ligand assemblies is still challenging as well-defined design strategies are unknown for obtaining these crystalline solids in non-centrosymmetric structures. Herein, we report a new discrete octahedral metal-organic cage [Cu₆(TPPA)₈(H₂O)₁₂].(NO₃)₁₂.32H₂O] (1) by employing a tripodal phosphoramideligand, [PO(NH³Py)₃] (TPPA). Ferroelectric measurements on 1 showed improved polarizationvs. the electric field (P-E) hysteresis loop characteristics than those observed for similar cages, with a sizableremnant polarization (P_r) value of 39.2 μC/cm². The non-centrosymmetric structure of 1 can be tracked to the uniform rotation of the octahedra around the metal centre. At the same time, the polarization in the framework stems from the toggling of the disordered nitrate anions. The temperature-dependent dielectric constant measurements on 1 showed a desolvation-assisted dielectric relaxation behaviour, indicating the involvement of solvate molecules in establishing the long-range polar order.

A new discrete octahedral metal-ligand cage was prepared by employing a flexible tripodal phosphoramide ligand. The polarization in this assembly originates from the toggling of the nitrate anions and its long-range order assisted by solvate molecules of water. The ferroelectric measurements of the cage gave a well-defined rectangular P-E hysteresis loop with a remnant polarization value.