Electroactive Organic Cage as Efficient Adsorbent and Ultrasensitive Transistor Sensor for Trace Iodine

Abstract Efficient capture and ultrasensitive detection of radioiodine from nuclear industrial waste and contaminated water are crucial for environmental safety, yet achieving both simultaneously with a single material remains challenging. Here, a tetrathiafulvalene (TTF)decorated organic cage (TTFcage) is reported that serves as a high‐performance adsorbent for trace iodine (I 2 ) in both industrial off‐gas and polluted water, and as a molecular cagebased organic field‐effect transistor (cOFET) for ultrasensitive I 2 detection. TTFcage shows strong I 2 affinity through cooperative charge‐transfer interactions of N and S sites, resulting in an ultrahigh I 2 vapor uptake of 1.28 g g −1 under >150 °C and <150 ppmv of I 2 conditions, 7.1 times higher than industrial silver adsorbents. It also decontaminates iodine in flowing water below the secure criteria of World Health Organization (WHO, <0.1 ppm) with a high adsorption capacity of 5.16 g g −1 . The electroactive TTF units impart tunable conductivity upon I 2 binding, enabling an unreported cOFET sensor with a limit of detection (LoD) of I 2 as low as 0.58 ppt (≈10 −12 M), exceeding conventional spectroscopic methods by 6 orders of magnitude. Moreover, I 2 adsorption and detection can be integrated into a miniaturized chip, providing a portable platform for on‐site pollution treatment and synchronized environmental monitoring of radioiodine.