Zhang Shuai-Long, Guo Zhong-Cheng, Su An-Ran, Yang Jian, Li Zi-Feng, Si Yu-Bing, Li Gang
College of Chemistry and Green Catalysis Center, Zhengzhou University, Zhengzhou, 450001, Henan, P.R. China.
Chemistry. 2023 Oct 13;29(57):e202302146. doi: 10.1002/chem.202302146. Epub 2023 Sep 5.
This work elucidates the potential impact of intramolecular H-bonds within the pore walls of covalent organic frameworks (COFs) on proton conductivity. Employing DaTta and TaTta as representative hosts, it was observed that their innate proton conductivities (σ) are both unsatisfactory and σ(DaTta)<σ(TaTta). Intriguingly, the performance of both imidazole-loaded products, Im@DaTta and Im@TaTta is greatly improved, and the σ of Im@DaTta (0.91×10 S cm ) even surpasses that of Im@TaTta (3.73×10 S cm ) under 100 °C and 98 % relative humidity. The structural analysis, gas adsorption tests, and activation energy calculations forecast the influence of imidazole on the H-bonded system within the framework, leading to observed changes in proton conductivity. It is hypothesized that intramolecular H-bonds within the COF framework impede efficient proton transmission. Nevertheless, the inclusion of an imidazole group disrupts these intramolecular bonds, leading to the formation of an abundance of intermolecular H-bonds within the pore channels, thus contributing to a dramatic increase in proton conductivity. The related calculation of Density Functional Theory (DFT) provides further evidence for this inference.
这项工作阐明了共价有机框架（COF）孔壁内分子内氢键对质子传导率的潜在影响。以DaTta和TaTta作为代表性主体，观察到它们的固有质子传导率（σ）都不尽人意，且σ（DaTta）<σ（TaTta）。有趣的是，两种负载咪唑的产物Im@DaTta和Im@TaTta的性能都有很大提高，在100°C和98%相对湿度下，Im@DaTta的σ（0.91×10 S cm）甚至超过了Im@TaTta的σ（3.73×10 S cm）。结构分析、气体吸附测试和活化能计算预测了咪唑对框架内氢键系统的影响，导致观察到质子传导率的变化。据推测，COF框架内的分子内氢键阻碍了有效的质子传输。然而，咪唑基团的加入破坏了这些分子内键，导致孔道内形成大量分子间氢键，从而使质子传导率显著增加。密度泛函理论（DFT）的相关计算为这一推断提供了进一步的证据。
