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 o–p–m-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.

中文翻译：

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使用 MOF 薄膜传感器阵列检测 VOC 混合物：检测和区分二甲苯异构体及其三元混合物

挥发性有机化合物 (VOC) 的检测和识别在许多应用中都至关重要。虽然可以通过各种传感器检测纯 VOC，但对混合物中 VOC（尤其是类似分子）的区分受到交叉敏感性的阻碍。混合物中的异构体鉴定更加困难。金属有机框架 (MOF) 具有明确的、纳米多孔的和多功能结构，有可能通过调整吸附亲和力来提高 VOC 传感性能。在这里，我们通过使用六种重量、石英晶体微天平 (QCM) 传感器阵列检测和识别三元二甲苯异构体混合物，该传感器涂有具有不同异构体亲和力的选定 MOF 薄膜。我们使用经典的分子模拟来深入了解传感机制。除了分析物和 MOF 膜之间的有吸引力的相互作用外，异构体的区分是由刚性晶体框架空间控制异构体进入 MOF 中的不同吸附位点引起的。传感器阵列对每种纯异构体的检测限非常低，为 1 ppm，并允许在混合物中区分异构体。在 100 ppm 时，有 16 种不同的三元o – p – m-二甲苯混合物的分类准确度很高（96.5%）。这项工作展示了 MOF 传感器阵列（也称为 MOF 电子鼻（MOF-e-nose））在传感 VOC 混合物方面的空前性能。基于该研究，还提供了检测和区分挥发性分子复杂混合物的指南。