High-performance specific detection of NO2 based on PCN-222-Mn doped with Bi electron mediator

Continuous real-time monitoring of hazardous gases is essential for safeguarding public health and environmental integrity, necessitating the utilization of highly selective and sensitive gas sensors. Herein, the chemiresistive sensor for NO2 was fabricated based on Bi nanoparticles (NPs) doped Mn-porphyrin MOF PCN-222-Mn (Bi@PCN-222-Mn) through a straightforward in situ reduction process. Bi NPs serve as electron donors, facilitating the migration of electrons towards the PCN-222-Mn through the formation of a Schottky barrier caused by electrostatic interaction. Besides the Mn-porphyrin as detecting site in PCN-222-Mn, the Bi NPs in Bi@PCN-222-Mn act as supportive sites, enabling NO2 adsorption and electron transfer to NO2 simultaneously, thus enhancing the response signal amplification. Consequently, Bi@PCN-222-Mn exhibited the specific sensing for NO2 with 5 times higher sensitivity (238.6 % ppm−1) in the range of 0.05–2 ppm and a lower limit of detection (LOD) (13 ppb) compared to PCN-222-Mn. Moreover, the Bi@PCN-222-Mn-based chemiresistive sensor also exhibited outstanding long-term stability and moisture resistance, applicable for the practical detection of NO2. These results prove the feasibility of improvement of gas detection performance by introducing metal NPs as electron mediator and an idea for the application of MOFs in gas sensing.