High-performance NO2 gas sensors based on vanadium metal organic frameworks (V-MOFs) on flexible graphene electrodes

This research aimed to prepare vanadium metal organic frameworks (V-MOFs) with the organic ligands of terephthalic acid (PTA) and pyromellitic acid (PMA) by a one-step hydrothermal process. Organic ligands were pyrolyzed and the vanadium ion was oxidized after calcination to prepare V-MOF(PTA) and V-MOF(PMA) as NO2 gas detection materials. The interdigital electrodes were performed by CO2 laser induced polyimide films with porous graphene for flexible gas sensors. Characteristics of the synthesized material were examined and analyzed, including surface morphology, chemical composition, crystal property, and specific surface area. Furthermore, the sensor characteristics of the response, response/recovery time (t(s)/t(c)), repeatability, selectivity, and stability were tested by an ultraprecision electrometer. After gas detection, the V-MOF120(PTA)-based gas sensor demonstrated a highest response of average 800.8 % at 100 ppm NO2, fast t(s)/t(c) of average 230/39.8 s, a minimum sensing limit of 1 ppm, and excellent stability and repeatability. Additionally, the proposed sensor had good gas selectivity for NO2 compared to ethanol, methanol, acetone, and ammonia under a concentration of 100 ppm at room temperature.