Detecting and monitoring volatile organic compounds (VOCs) at ppm concentrations presents significant challenges but is vital across various sectors, including healthcare for disease diagnosis and environmental monitoring for air quality assessment. Conventional methods, primarily involving semiconducting metal oxide (SMOx) sensors, are widely used due to their cost-effectiveness, high sensitivity, and rapid response rates. These sensors function by exhibiting changes in resistivity when exposed to VOCs. Despite their advantages, SMOx sensors have notable limitations, such as reduced lifespan, low selectivity, requirement of high operational temperatures (typically 200-300 °C), and issues like baseline drifts that compromise data reliability.
To address these selectivity challenges, the concept of an electronic nose (E-nose) has been developed, which involves an array of SMOx sensors, each with partial selectivity to different VOCs and background interferences. The idea is that by combining the multivariate responses from these sensors, specific VOCs can be identified even in complex environments. However, the effectiveness of current E-nose designs is hindered by the high correlation in responses among the sensor elements, leading to two main issues: either the array is too small to cover the required chemical diversity, or it becomes overly large, leading to increased costs and power consumption.
In response to these limitations, there is a growing demand for innovative VOC sensing technologies.The MOFFET project proposes a departure from traditional SMOx sensors, focusing instead on metal-organic frameworks (MOFs). MOFs are unique for their microporous, crystalline structures formed from metal ions linked by organic ligands. Their sub-nanometer pores and customizable pore walls make MOFs exceptionally capable of capturing VOCs, even at trace levels. While achieving perfect selectivity for a specific VOC in a complex background may be overly optimistic, an array of MOFs, each with different adsorption characteristics, can function effectively as an E-nose.
