Ferroelectric Behavior of an Octahedral Metal‐Ligand Cage and Its 2D‐Connected Cage Framework

Abstract

Supramolecular systems hold great potential as ferroelectric materials because they are easy to prepare and do not require toxic and environmentally damaging elements. However, directing the self‐assembly process of a supramolecular array to yield polarizable solids is still challenging. Here, we describe induced ferroelectricity in a supramolecular framework of metal‐organic cages that are supported by a flexible tripodal ligand (NHCH2‐(3‐Py))3PO (TPPA). Ferroelectric responses on the discrete cage [Cu6(H2O)12(TPPA)8](NO3)12 ⋅ 45H2O (1) and its 2D‐connected framework [{Cu6Cl4(H2O)6(TPPA)8}(NO3)8 ⋅ 60H2O]n (2) yielded well‐resolved rectangular hysteresis loops at room temperature with remnant polarization values of 27.27 and 29.09 μC/cm2, respectively. Thermal hysteresis measurements (THM) and capacitance‐voltage (C−V) plots further corroborate the ferroelectric behavior in these compounds. The polarization in them is due to the displacements of solvated molecules and nitrate ions in the pockets of these frameworks.