Precise and rapid oxygen sensing is crucial in a wide range of applications, from industrial process control to environmental monitoring and medical devices. In this proof-of-concept study, we present a new type of gas-phase oxygen sensing system that combines electron paramagnetic resonance (EPR) detection with a custom-designed sensing material: a metal-organic framework ZIF-8 composite with an embedded nitroxide spin probe. To enhance the sensing performance, we adapted the continuous wave EPR experiment protocol and optimized both the material structure and the gas delivery system. Static and flow experiments with dynamic exchange of the analyzed gas mixture were carried out. The sensing system significantly outperforms commercially available industrial models. It demonstrated reliable detection over a broad oxygen concentration range (0.02 to 95%) and response times from 550 ms to 2 s without sacrificing the accuracy. Due to detection simplicity, the sensor module can be further optimized by embedding it into an EPR-on-a-chip device, reducing the price and the module size. The integration of spin probes into a porous engineered framework offers a powerful approach for developing accurate and tunable oxygen sensors, which can meet the demands of both industry and research.
Zhitkeyev et al. (2025) studied this question.