Miyazawa Satoru, Hosono Reina, Osuga Ryota, Kondo Junko Nomura, Uchida Sayaka
Department of Basic Science, School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguroku, Tokyo 153-8902, Japan.
Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259-R1-10 Nagatsuta, Midori-ku, Yokohama, Kanagawa 226-8503, Japan.
Acta Crystallogr C Struct Chem. 2018 Nov 1;74(Pt 11):1289-1294. doi: 10.1107/S2053229618008227. Epub 2018 Oct 17.
Proton conduction in crystalline porous materials has received much attention from basic scientific research through to practical applications. Polyoxometalates (POMs) can efficiently transport protons because of their small superficial negative charge density. A simple method for enhancing proton conductivity is to introduce NH into the crystal structure, because NH can form hydrogen bonds and function as a proton carrier. According to these considerations, NH was introduced into the porous structure of A[CrO(OOCH)(etpy)][α-SiWO]·nHO (A = Li, Na, K and Cs; etpy = 4-ethylpyridine) (I-A) via topotactic cation exchange. The resulting compound, diammonium tris(4-ethylpyridine)hexaformatooxidotrichromium α-silicododecatungstate hexahydrate, (NH)[Cr(CHO)O(CHN)][α-SiWO]·6HO, showed high proton conductivity and low activation energy under high relative humidity (RH), suggesting that protons migrate efficiently via rearrangement of the hydrogen-bonding network formed by the NH cations and the waters of crystallization (Grotthuss mechanism). The proton conductivity and activation energy greatly decreased and increased, respectively, with the decrease in RH, suggesting that protons migrate as NH and/or HO under low RH (vehicle mechanism).
从基础科学研究到实际应用，晶体多孔材料中的质子传导已受到广泛关注。多金属氧酸盐（POMs）因其较小的表面负电荷密度而能够有效地传输质子。增强质子传导性的一种简单方法是将NH引入晶体结构中，因为NH可以形成氢键并作为质子载体发挥作用。基于这些考虑，通过拓扑阳离子交换将NH引入到A[CrO(OOCH)(etpy)][α-SiWO]·nHO（A = Li、Na、K和Cs；etpy = 4-乙基吡啶）（I-A）的多孔结构中。所得化合物，二铵三（4-乙基吡啶）六甲酸氧化三铬α-硅十二钨酸盐六水合物，(NH)[Cr(CHO)O(CHN)][α-SiWO]·6HO，在高相对湿度（RH）下表现出高质子传导性和低活化能，这表明质子通过由NH阳离子和结晶水形成的氢键网络重排而有效地迁移（Grotthuss机制）。随着RH的降低，质子传导率和活化能分别大幅降低和升高，这表明在低RH下质子以NH和/或HO的形式迁移（载体机制）。
