Integrating {Cu _<i>x</i> I _<i>y</i> } Modules into a Series of Alkaline Earth Metal Based Metal–Organic Frameworks for NO ₂ Chemiresistive Sensing

Metal-organic frameworks (MOFs), emerging as a promising class of chemiresistive sensing materials operating at room temperature (RT), have garnered substantial attention in recent years. Herein, through tuning the coordination modes between isonicotinic acid (HINA) and alkaline earth (AE, AE = Mg, Ca, Ba) metals with different radii and varied coordination numbers, the bulk CuI can be tailored into one-dimensional (1D) chain-like and 2D layered {Cu_<i>x</i>I_<i>y</i>} modules during coordination assembly, which are encapsulated within the AE-INA frameworks to obtain a series of AE-CuI-INA MOFs. Significantly, these AE-CuI-INA show selective and sensitive gas sensing performances toward NO₂ working at room temperature, marking the first report of AE-CuI-INA MOFs for NO₂ sensing. The sensing mechanism was examined through various experimental techniques, including but not limited to PXRD, X-ray photoelectron spectroscopy (XPS), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). This work not only enriches the family of gas sensing MOFs but also provides valuable insights into the design of novel functional materials by utilizing {Cu_<i>x</i>I_<i>y</i>} modules as central sensing units.