Room-Temperature Quantitative Quantum Sensing of Lithium Ions with a Radical-Embedded Metal-Organic Framework

Recent advancements in quantum sensing have sparked transformative detection technologies with high sensitivity, precision, and spatial resolution. Owing to their atomic-level tunabi l i t y , molecular qubits and ensembles thereof are promising candidates for sensing chemical analytes. Here, we show quantum sensing of lithium ions in solution at room temperature with an ensemble of organic radicals integrated in a microporous metal- organic framework (MOF). The organic radicals exhibit electron spin coherence and microwave addressabi l i t y at room temperature, thus behaving as qubits. The high surface area of the MOF promotes accessibility of the guest analytes to the organic qubits, enabling unambiguous identification of lithium ions and quantitative measurement of their concentration through relaxo-metric and hyperfine spectroscopic methods based on electron paramagnetic resonance (EPR) spectroscopy. The sensing principle presented in this work is applicable to other metal ions with nonzero nuclear spin.

Automated summary

Recent advancements in quantum sensing have led to transformative detection technologies with high sensitivity, precision, and spatial resolution. In this study, organic radicals integrated in a microporous metal-organic framework (MOF) were used as qubits for quantum sensing of lithium ions in solution at room temperature. The high surface area of the MOF enabled easy accessibility of the lithium ions to the organic qubits, allowing for unambiguous identification and quantitative measurement of their concentration using relaxo-metric and hyperfine spectroscopic methods based on electron paramagnetic resonance (EPR) spectroscopy. The sensing principle presented in this work can be applied to other metal ions with nonzero nuclear spin.