Facile strategy for screening and fabricating metal-organic framework-based sensors for highly sensitive detection of iodine gas

Radioactive iodine gas detection has significant applications in the nuclear industry, particularly in nuclear accident scenarios and nuclear fuel reprocessing facilities. Herein, chemically stable metal-organic frameworks (MOFs) with good affinity for iodine (including Zn(1,3-BDP), UiO-66, UiO-66-NH₂, etc.) were computationally screened and drop-casted upon interdigitated electrodes (IDEs). These MOFs were used to develop advanced iodine sensors to achieve the direct electrical detection of I₂ gas via impedance spectroscopy measurements. Upon exposure to I₂ gas, a similar electrical response change has occurred for all the IDE sensors, despite in the different impedance ratio. In particular, UiO-66-coated sensors exhibited an impedance ratio > 10³ times, while the modification of amino groups (-NH₂) enhanced the sensitivity, exceeding 10⁴ times for UiO-66-NH₂, and was accompanied by a better iodine uptake. Notably, the sensors fabricated from Zn(1,3-BDP), which also contained nitrogen atoms, exhibited excellent comprehensive sensing performance, including high sensitivity (with impedance ratio achieving 1.4×10⁶ times), good recyclability, rapid response speed (with impedance change ratio of 250 times within 3 minutes), low detection limit (about 29 times under 300 ppm I₂ vapor at 25℃) and high anti-interference ability. Our theoretical calculations revealed that the underlying I₂ sensing mechanism could be attributed to a decreased band gap and enhanced electrical conductivity due to the new electronic states introduced by the adsorbed I₂. This work proposes a novel and feasible method for investigating sensing materials and strategies to fabricate high-performance iodine gas sensors, providing a basis for developing nuclear radioactivity monitoring technology and emergency security safeguard equipment.