Karlsruhe Institute of Technology (KIT), Institute of Functional Interfaces (IFG), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
Department of Chemical & Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, Unites States.
ACS Sens. 2022 Jun 24;7(6):1666-1675. doi: 10.1021/acssensors.2c00301. Epub 2022 Jun 8.
Detection and recognition of volatile organic compounds (VOCs) are crucial in many applications. While pure VOCs can be detected by various sensors, the discrimination of VOCs in mixtures, especially of similar molecules, is hindered by cross-sensitivities. Isomer identification in mixtures is even harder. Metal-organic frameworks (MOFs) with their well-defined, nanoporous, and versatile structures have the potential to improve the VOC sensing performance by tailoring the adsorption affinities. Here, we detect and identify ternary xylene isomer mixtures by using an array of six gravimetric, quartz crystal microbalance (QCM)-based sensors coated with selected MOF films with different isomer affinities. We use classical molecular simulations to provide insights into the sensing mechanism. In addition to the attractive interaction between the analytes and the MOF film, the isomer discrimination is caused by the rigid crystalline framework sterically controlling the access of the isomers to different adsorption sites in the MOFs. The sensor array has a very low limit of detection of 1 ppm for each pure isomer and allows the isomer discrimination in mixtures. At 100 ppm, 16 different ternary ---xylene mixtures were identified with high classification accuracy (96.5%). This work shows the unprecedented performance of MOF-sensor arrays, also referred to as MOF-electronic nose (MOF-e-nose), for sensing VOC mixtures. Based on the study, guidelines for detecting and discriminating complex mixtures of volatile molecules are also provided.
挥发性有机化合物（VOCs）的检测和识别在许多应用中至关重要。虽然各种传感器可以检测纯 VOCs，但混合物中 VOCs 的区分，特别是相似分子的区分，受到交叉敏感性的阻碍。混合物中的异构体识别更加困难。金属有机骨架（MOFs）具有明确的纳米多孔和多功能结构，通过调整吸附亲和力，有可能改善 VOC 传感性能。在这里，我们使用涂有具有不同异构体亲和力的选定 MOF 薄膜的六个重量法、石英晶体微天平（QCM）基传感器阵列来检测和识别三元二甲苯异构体混合物。我们使用经典分子模拟来深入了解传感机制。除了分析物与 MOF 薄膜之间的吸引力外，异构体的区分还归因于刚性结晶骨架在空间上控制异构体进入 MOF 中不同吸附位的能力。该传感器阵列对每种纯异构体的检测限非常低，为 1ppm，并且可以在混合物中进行异构体的区分。在 100ppm 时，16 种不同的三元---二甲苯混合物被高分类准确率（96.5%）识别。这项工作展示了 MOF-传感器阵列（也称为 MOF-电子鼻（MOF-e-nose））在感测 VOC 混合物方面的前所未有的性能。基于该研究，还提供了用于检测和区分复杂挥发性分子混合物的指导方针。
