面内ひずみを水で調節して2次元MOFの空間反転対称性を破る~巨大分極を示す強誘電イオン伝導体開発のための新構造モチーフ~

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2025-06-26 九州大学

九州大学らの研究チームは、空間反転対称性を破った二次元MOF「[Mn(salen)]₂[ReN(CN)₄(MeCN)]・H₂O」を開発し、従来の約1000倍の分極を示す強誘電プロトン伝導体であることを発見した。水による面内ひずみで極性が発現し、分極とイオン移動が同期する新機構も確認。水蒸気に応答するSHG変換も可能で、燃料電池等への応用が期待される。成果は英誌「Chemical Science」に掲載。

面内ひずみを水で調節して2次元MOFの空間反転対称性を破る~巨大分極を示す強誘電イオン伝導体開発のための新構造モチーフ~
(参考図1)今回報告した波打ち構造を有する二次元強誘電イオン伝導体の結晶構造と強誘電ヒステリシス(※6)。

<関連情報>

二次元配位高分子の面内対称性の破れによる巨大分極を示す強誘電性プロトン伝導体 A ferroelectric proton conductor with colossal polarization induced by in-plane symmetry breaking in a two-dimensional coordination polymer

Yanqing Song,Yuta Tsuji, Kunihisa Sugimoto,Takashi Kikuchi,Yuxin Shi,Yusuke Murakami,Kotaro Hiramatsu, Benjamin Le Ouay, Masaaki Ohba and Ryo Ohtani
Chemical Science  Published:26 Jun 2025
DOI:https://doi.org/10.1039/D4SC08700C

Abstract

Noncentrosymmetric two-dimensional (2D) coordination polymers/metal–organic frameworks (CPs/MOFs) are very rare and their functionalities have not been explored. Herein, we report the first 2D ferroelectric proton conductor based on cyanido-bridged undulating 2D CPs. [Mn(salen)]2[ReN(CN)4(MeCN)]·H2O (MnReMeCN·H2O) crystallized in the Pna21 space group and underwent in-plane symmetry breaking upon incorporation of water within the crystal layers. Thus, the dehydrated MnReMeCN layers were centrosymmetric and exhibited reversible switching of second harmonic generation induced by water vapor. The ferroelectricity of MnReMeCN·H2O was strongly coupled with ion conduction, yielding a colossal polarization of 21 mC cm−2, which was determined via positive-up–negative-down measurements at 0.005 Hz and 298 K for single crystals. Moreover, MnReMeCN exhibited anisotropic thermal expansion based on the undulation change, while the zigzag angle changes of the layers switched between a decrease and an increase at around 300 K. These transformations corroborate the characteristic relationship between the zigzag pitch and the interlayer interaction of the undulating layered structures.

0500化学一般
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