Visual and Gravimetric CO2 Sensing at High Humidity Levels Enabled by MOF‐804 Cofunctionalized with Ionic Liquid and m‐Cresol Purple

Abstract Real‐time monitoring of carbon dioxide (CO 2 ) is imperative for medical diagnosis and effective environmental preservation. Despite the formidable challenge posed by the inherent chemical inertness of CO₂ molecules, a pioneering CO 2 sensor based on MOF‐804 cofunctionalized with ionic liquid (IL) and m‐cresol purple (mCP) is successfully developed. By ingeniously integrating hydrogen bonding, electrostatic interactions, and hydrophobic properties within the sensitive layer, the sensor achieves a state‐of‐the‐art sensitivity (Δf = 384 Hz), an exceptionally vast detection range spanning 400–80 000 ppm, and remarkable stability with minimal sensitivity drift even at relative humidity (RH) levels exceeding 80%. Furthermore, the inherent gasochromic property, stemming from the zwitterionic mechanism, paves the way for innovative self‐sustaining CO 2 test strips and groundbreaking applications, including CO 2 tracking and CO 2 ‐encrypted security labeling technology. Collectively, the realization of this ultra‐sensitive and robust CO 2 monitoring approach, coupled with its CO 2 ‐triggered visual and multifunctional capabilities, opens up novel avenues for dynamic CO 2 detection, advanced military encryption strategies, and enhanced health management systems.