Effective Enhancement of the Ferroelectric Performance of Polar Co-Gallate MOF by Doping M²⁺ Ions (M = Mg, Mn, Ni) into Framework Nodes

Abstract

MOF ferroelectrics have been demonstrated to be a promising candidate owing to various structures and controllable properties. However, weak ferroelectricity hampers their boom. Herein, a convenient strategy, doping metal ions into the framework nodes of parent MOF, is adopted to enhance ferroelectric performance. A series of M-doped Co-Gallate (M = Mg, Mn, Ni) were synthesized to improve ferroelectric properties. The electrical hysteresis loop demonstrated its ferroelectric behaviors, exhibiting obviously improved ferroelectric properties compared with the parent Co-Gallate. The remanent polarization was enhanced by two times for Mg-doped Co-Gallate, six times for Mn-doped Co-Gallate, and four times for Ni-doped Co-Gallate. The promoted ferroelectric performances are ascribed to the enhanced polarity of the overall structure triggered by framework distortion. Intriguingly, ferroelectric behaviors increase in the order Mg < Ni < Mn, displaying the same tendency as the difference value in the ionic radius between Co 2+ ions and M 2+ metal ions (M = Mg, Mn, Ni). These results demonstrate doping of metal ions is a valid strategy to enhance ferroelectric performances, which may serve as a guide in modulating ferroelectric behaviors.