0D Zinc OIMHs with Pyridine Vapor‐Activated NIR Fluorescence Emission Behavior for Gas Sensing

Abstract Pyridine is a common toxic volatile organic compound (VOC) that poses severe threats to the human respiratory and nervous systems. Consequently, developing effective sensing materials for its detection in ambient air is of great importance. In the study, three 0D organic–inorganic metal halides (OIMHs) are successfully synthesized by employing [ZnX ₄ ] ²⁻ (X = Cl, Br, I) as the metal halide center and protonated N,N ‐diphenyl‐4‐(quinolin‐5‐yl)aniline (5‐DQL) as the organic component, and are subsequently applied, for the first time, to pyridine vapor detection. Among them, the iodide‐based compound (5‐DQL‐H) ₂ ZnI ₄ exhibits a rare near‐infrared (NIR) luminescence response. Subsequently, the photophysical behavior and sensing mechanism are investigated through a series of characterization techniques and density functional theory (DFT) calculations. Additionally, a paper‐based sensor fabricated with (5‐DQL‐H) ₂ ZnI ₄ demonstrates excellent sensing performance, with a well‐defined linear correlation between the red/green (R/G) value in the fluorescence within the pyridine concentration range of 5.0 to 500.0 ppm, and the limit of detection (LOD) as low as 3.4 ppm. The intrinsic relationships among the crystal structure, photophysical properties, sensing performance, and electronic structure of OIMHs are systematically investigated in this work, thereby providing novel insights for the design of advanced fluorescent sensing materials.