Nitrogen dioxide (NO2), a significant pollutant from industrial sources, poses serious environmental risks. Developing sensors for accurate room-temperature detection of low-concentration NO2 is thus crucial. This study synthesized Keggin-type crystalline CoPOMs hydrothermally and integrated them into nanofibers (CoPOMs@NF) via electrospinning. Sensors fabricated from CoPOMs@NF calcined at varying temperatures (denoted CoPOMs@NF-x) successfully addressed the challenge of room-temperature (23 °C) NO2 detection. The CoPOMs@NF-3 sensor exhibited optimal performance, achieving a response ratio of ~1.163 toward 20 ppm NO2 at 23 °C, with rapid response/recovery times (9 s and 27 s, respectively). It demonstrated a wide detection range (2-120 ppm), a low detection limit (LOD) of 294 ppb, and excellent selectivity, repeatability, and long-term stability. This enhanced gas sensitivity is attributed to abundant oxygen-containing functional groups on CoPOMs and hydroxyl groups generated during calcination, providing active sites for gas adsorption. Integrating crystalline materials with electrospinning proves an effective strategy for advancing NO2 sensing, expanding the potential of polyoxometalates (POMs) in practical gas sensor application.
