Parts-per-billion (ppb) selective iodine sensors leveraging metal–organic framework nanoenvironment

Ultra-sensitive and highly selective iodine gas sensors play a crucial role during the nuclear radiation leak for a timely detection and mitigation of pollution, ensuring the safety of a vast number of operators and subsequent integrity of the facility. Herein, we rationally designed a metal–organic framework (MOF) that exhibits an outstanding performance with an almost billionfold enhancement in the electrical response due to its optimized hydrophobicity, which allows the easy migration of iodine molecules through the channels and the presence of suitable interaction sites, temporarily anchoring the target molecule for ultra-trace sensing. The prototype sensor tested in demanding environments demonstrates its high selectivity, ultra-trace parts per billion (ppb)-level sensitivity, good reversibility, and a very fast response time even at high frequencies compared to existing adsorbents, including commercially available materials. Further, the iodine sensing at the atomic level was studied in detail by measuring the electrical response of a single crystal and, the optimal thickness of the MOF layer was identified for an industrially-viable prototype sensor by using inkjet printing. In a wider perspective, we propose a general strategy for engineering electrically efficient sensing materials that will enable the construction of high-sensitivity iodine sensors targeting a safe and sustainable future.