Exploration of a new type of water-stable proton conducting material is of great interest owing to its applications as an electrolytic material in proton exchange membrane fuel cells (PEMFC). Herein, we report four such new metal organic frameworks of Cd(II) and Co(II) containing a new linear bis-pyridyl-tris-amide ligand (L) and angular dicarboxylates 4,4′-oxybisbenzoic acid (OBA) and benzene-1,3-diacrylic acid (BDA) as linkers. The MOFs are found to exhibit a general formula of {[M(L)(dicarboxylate)]·xDMF·yH₂O}_n with varying amounts of solvent. Two MOFs containing BDA exhibited two-dimensional rectangular grid-like networks with grid dimensions of 25 × 23 Ų, while those with OBA exhibited 3D-networks consisting of the mab topology with rectangular channels of dimensions 31 × 21 Ų and 31 × 17 Ų. All four exhibited a solvent accessible volume of 36–49%. AC impedance analyses on MOFs 1–4 reveal that they exhibit appreciable proton conductivities (PC): σ = 2.2 × 10⁻³, 9.5 × 10⁻⁴, 1.2 × 10⁻³ and 6.6 × 10⁻⁴ S cm⁻¹, respectively, at 353 K and 98% relative humidity (RH). The high PC values could be attributed to the hydrogen bonding between water molecules and also with amides and carboxylates of the framework. Furthermore, a gas sorption study revealed that MOFs 1–4 show preferential adsorption of water vapor (195–330 cc g⁻¹ at p/p₀ ∼ 1) over nitrogen given the hydrophilic nature of the channels and the stability of MOFs under humid conditions. In addition, all these materials have shown capability in selectively adsorbing cationic dyes (methylene blue, MB and crystal violet, CV).

中文翻译：

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含有线性双吡啶基三酰胺和角羧酸盐的MOF：质子电导率，水蒸气和染料吸附的研究†

由于新型的水稳定性质子传导材料作为质子交换膜燃料电池（PEMFC）中的电解质材料的应用而引起了人们的极大兴趣。在这里，我们报告了四个这样的新的Cd（II）和Co（II）的金属有机骨架，它们包含新的线性双吡啶基三酰胺配体（L）和角二羧酸4,4'-氧双苯甲酸（OBA）和苯-1,3-二丙烯酸（BDA）作为接头。发现MOF的通式为{[M（L）（二羧酸盐）]· x DMF· y H ₂ O} _n用不同量的溶剂。含有BDA两个MOFs材料表现出的二维矩形网格状以25×23的网格尺寸网²，而那些与OBA表现出由所述的3D-网络单抗与尺寸31×21埃的矩形通道拓扑²和31×17埃²。所有这四个样品均显示出36-49％的溶剂可及体积。AC阻抗上的MOF分析1-4表明，它们显示出明显的质子传导（PC）：σ = 2.2×10 ^-3，9.5×10 ^-4，1.2×10 ^-3和6.6×10 ^-4小号厘米^-1分别在353 K和98％相对湿度（RH）下。高PC值可归因于水分子之间的氢键以及骨架的酰胺和羧酸盐。此外，气体吸附研究揭示的MOF 1-4显示优先吸附的水蒸汽（195-330毫升克^-1在p / p ₀以上氮〜1）中给出的信道的亲水性质和MOFs材料在潮湿的稳定性条件。此外，所有这些材料均具有选择性吸附阳离子染料（亚甲基蓝，MB和结晶紫，CV）的能力。