Crystal structures and ferroelectric properties of homochiral metal organic frameworks constructed from a single chiral ligand
MOFs have been proven to be promising candidates for designing ferroelectric materials. Herein two new homochiral Co-MOF-1 and Co-MOF-2 have been synthesized by using the chiral ligand HL (HL= phenyl-((pyridin-4-ylmethyl)-amino)-acetic acid) and Co(NO3)2·6H2O. Co-MOF-1 was obtained via two-step synthesis involving hydrogel to Zn-MOF conversion and dissolution-recrystallization process. Co-MOF-2 was directly synthesized by the coordination reaction between chiral ligand HL and Co(NO3)2·6H2O under hydrothermal condition. We investigate the correlations between ferroelectric properties and crystal structure, the ferroelectric properties of Co-MOF-1 and Co-MOF-2 are drastically different. Indeed, Co-MOF-2 shows obvious hysteretic behavior while no clear electric hysteresis loop is discovered for Co-MOF-1. These significant disparities might be attributed to the different molecular dipole moment in Co-MOF-1 and Co-MOF-2. The different octahedral coordination units of molecular structure in Co-MOFs may alter dipole moment of molecule, thus resulting in the absence of hysteresis loop in Co-MOF-1.