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A 2D Mg(II)-MOF with High Density of Coordinated Waters as Sole Intrinsic Proton Sources for Ultrahigh Superprotonic Conduction
ACS Materials Letters ( IF 9.6 ) Pub Date : 2020-09-17 , DOI: 10.1021/acsmaterialslett.0c00358
Santanu Chand 1 , Shyam Chand Pal 1 , Dae-Woon Lim 2 , Kazuya Otsubo 2 , Arun Pal 1 , Hiroshi Kitagawa 2 , Madhab C. Das 1
Affiliation  

As an important type of crystalline solid proton-conducting material, metal-organic frameworks (MOFs) have received immense attention in the scientific community. In general, such MOFs are designed with intrinsic (H3O+, NH4+, Me2NH2+, H2PO4, OH located in pores or dangling −SO3H, −COOH, and −PO3H2 groups as integral parts of the backbone) or extrinsic proton sources (imidazole, triazole, histamine, H3PO4, H2SO4 as guests). It has long been known that metal ions enhance the acidity of coordinated H2O molecules; however, such metal ion-bound water molecules as sole intrinsic proton sources for the construction of MOF-based conductors are largely unexplored. By exploiting such a design principle, herein, we report the proton-conduction properties of Mg-OBA MOF with the molecular formula {[Mg2(OBA)2(H2O)6]·2H2O}n [OBA = 4,4′-oxybis(benzoic acid)], where half of the octahedral coordination sites around Mg(II) centers are occupied by water molecules. The 2D layered structure with hydrophilic interlayer spaces within the framework having abundant water coordination as the sole proton sources makes extended H-bonding pathway for efficient protons migration and thus exhibiting ultrahigh conductivity with the value of 1.27 × 10–2 S cm–1 at 80 °C and 95% relative humidity (RH). The activation energy (Ea = 0.13 eV) obtained is one of the lowest of MOF-based proton conductors suggesting facile proton transfer. Besides, this material is quite robust and easy to scale up in the aqueous medium.

中文翻译:

具有高浓度配位水的二维Mg(II)-MOF作为超高质子传导的唯一本征质子源

作为一种重要的晶体固体质子传导材料,金属有机骨架(MOF)在科学界引起了极大的关注。通常,这样的MOF设计具有固有(H 3 ö +,NH 4 +中,Me 2 NH 2 +,H 2 PO 4 -,OH -位于孔或悬空-SO 3 H,-COOH,和-PO 3 H 2基团作为骨架的组成部分)或外在质子源(咪唑,三唑,组胺,H 3 PO 4,H 2 SO 4作为客人)。早就知道金属离子会增强配位的H 2 O分子的酸度。然而,这种金属离子束缚的水分子作为基于MOF的导体的唯一固有质子源尚未得到充分研究。通过利用这种设计原理,我们在本文中报道了分子式为{[Mg 2(OBA)2(H 2 O)6 ]·2H 2 O} nMg-OBA MOF的质子传导性质。[OBA = 4,4'-oxybis(benzoic acid)],其中Mg(II)中心周围的八面体配位位点的一半被水分子占据。框架内具有亲水性中间层空间的二维层状结构具有丰富的水配位作为唯一的质子源,为有效的质子迁移提供了扩展的氢键途径,因此在80时具有1.27×10 –2 S cm –1的超高电导率°C和95%相对湿度(RH)。所获得的活化能(E a = 0.13 eV)是最低的基于MOF的质子导体之一,表明质子转移容易。此外,该材料非常坚固并且易于在水性介质中按比例放大。
更新日期:2020-10-05
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