Humidity InducedProton–Electron ConductingMetal–Organic Frameworks of M₃(Hexaiminobenzene)₂ (M = Ni, Cu, Fe) for Highly Sensitivity Drug Precursor ChemicalsGases Detection

Exploiting high-performance gas sensors is desirable for the on-site and accurate detection of drug precursor chemical gases. Here, the electron–proton conductivity metal–organic frameworks M₃(HIB)₂ were designed to discriminate typical drug precursor chemical gases. The strong d-π conjugation and substantial H₂O ligands in M₃(HIB)₂ generate conducting pathways for electrons and protons, which contribute to novel gas-sensing properties. Remarkably, Fe₃(HIB)₂ demonstrates an ultrahigh response of over 379 toward 60 ppm of toluene at room temperature (RT). Furthermore, the adsorption/desorption behaviors of M₃(HIB)₂ can be tuned by systematically varying the metal center, causing distinctive gas sensing features for pattern recognition of drug precursor chemical gases. The recognition model was constructed using a convolutional neural networks-gated recurrent unit (CNN-GRU) algorithm, exhibiting a high recognition accuracy. The sensing mechanism is revealed by the Lewis and Brønsted acid site adsorption, due to competitive adsorption between H₂O and analyte gases. This work paves the way for the development of proton–electron dual-conducting MOFs for high-performance gas sensors.