摘要/Abstract

氮杂环化合物咪唑、三氮唑等常被负载在多孔材料中应用于质子传导.受此启发，利用结构中含有三氮唑的2H，2'H-3，3'-双-1，2，4-三唑-5，5'-二胺（BTDA）作为建构单元，与2，4，6-三甲酰基间苯三酚（TFP）发生希夫碱缩合反应合成一种新型二维共价有机框架（TFP-BTDA-COF）.通过理论模拟、粉末X射线衍射（PXRD）、氮气吸附-解吸表征和傅里叶变换红外光谱（FTIR）等证实了其结构.由于2D-COF的π-π堆积作用，BTDA连接单元中三氮唑上的N-H键在COF各层上周期性间隔排列形成有序阵列，在一定湿度条件下，借助水分子的中继作用，质子可以沿该阵列在一维孔道内传递，使得该COF具备通过骨架进行质子传导的能力.采用交流阻抗法对其质子传导能力进行测试，测试结果表明：随环境湿度增大，材料的质子传导能力逐渐增强，在98%相对湿度下达到最大值1.4×10^-3 S·cm^-1.
关键词: 共价有机框架, 质子传导, 晶体结构, 交流阻抗
Nitrogen heterocyclic compound like imidazole and triazole are often loaded in porous material for proton conduction. Inspired by this, we employ 5,5'-diamino-3,3'-bis(1H-1,2,4-triazole) (BTDA) containing triazole fragments in the structure as the construction unit to react with 2,4,6-triformylphloroglucinol (TFP) through Schiff-base condensation reaction to synthesize a novel two-dimensional covalent organic framework named TFP-BTDA-COF. The theoretical results were simulated using the Accelrys Material Studios 7.0 software package and compared with the powder X-ray diffraction (PXRD) test data to confirm the crystal structure of TFP-BTDA-COF. The porosity and pore structure of TFP-BTDA-COF were characterized by N₂ adsorption-desorption at 77 K. The condensation reaction was confirmed by Fourier transform infrared spectroscopy (FTIR). Due to the π-π accumulation of the 2D-COF, the N-H bond of the triazole in BTDA connecting unit is periodically and regularly arranged on each layer of the COF to form an ordered array. Under certain humidity conditions, the protons can be transmitted along the array in the one-dimensional pore channel by the intermediary of water molecules. Therefore, the TFP-BTDA-COF has the ability to conduct proton through the skeleton. The proton conductivity of TFP-BTDA-COF is tested by the AC impedance method. The results show that the proton conductivity of the material is gradually enhanced with the increase of the ambient humidity, and the maximum value is 1.4×10^-3 S·cm^-1 at 98% relative humidity. The PXRD of TFP-BTDA-COF in boiling water for 2 h and after 12 h AC impedance test were compared with the original experimental value to evaluate its tolerance under the working conditions of the proton membrane fuel cell. The PXRD diffraction peak intensity did not change obviously compared with that of the original experimental value. The thermogravimetric analysis results show that the thermal stability of TFP-BTDA-COF can reach high to 400℃. The above evidence proves that it has the potential to be used in proton membrane fuel cells.
Key words: covalent organic framework, proton conduction, crystal structure, AC impedance


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