Ligand spin immobilization in metal-organic frameworks enables high-performance chemispintronic detection of radical gas molecules.

The precise quantification of gaseous radicals in exhaled breath, such as fractional exhaled nitric oxide, serves as an invaluable noninvasive clinical diagnosis particularly in discerning various respiratory disorders. To date, the development of high-performance nitric oxide sensors compatible to modern electronic devices remains fundamentally challenging. We report that metal-organic frameworks (MOFs) with ligand spin immobilization demonstrate superior chemispintronic sensitivity and selectivity toward nitric oxide. Tetrathiafulvalene radical cations (TTF·+) within the MOF lattice considerably enhance the nitric oxide recognition via spin exchange interactions, leading to a five-order of magnitude reduction in the limit of detection (LOD), as compared to volatile organic compounds (VOCs) via carrier-doping mechanism. Record-low LOD of 0.12 parts per billion was achieved in M-TTF-spin (M = cobalt, zinc, and cadmium) MOFs, which also demonstrates exceptional selectivity over typical nitrogen oxides (NOx) and VOCs. This work opens up a distinct sensing platform for radical-like analytes through strategic design of spin-immobilized molecular functional motifs toward the spintronic device configurations.