Ultrasensitive Room-Temperature Detection of Nitrogen Oxides Using Bi ₂ S ₃ Derived from a Bismuth-Based Metal–Organic Framework

Nitrogen oxides (NOX) pose significant risks to human health and the environment even at low concentrations, which makes their detection at trace levels increasingly important. However, the development of high-performance gas sensors operating at room temperature for monitoring nitrogen oxides (NOX) remains a significant challenge, primarily due to the poor sensitivity and selectivity of most sensing materials under ambient conditions. Herein, we report a bismuth-based metal-organic framework (Bi-MOF) template strategy to synthesize orthorhombic Bi₂S₃ with a fiber-like architecture for exceptional NOX detection. The Bi-MOF precursor was synthesized via a solvothermal route and subsequently converted to Bi₂S₃ through sulfidation. FTIR, XPS, and BET analyses were carried out to investigate the surface chemistry and textural properties of the sensitive material. The as-prepared Bi₂S₃-based sensor demonstrates extraordinary responses to trace-level NOX gases at room temperature, exhibiting a colossal response of 655.65% to 0.5 ppm NO₂ and a significant response of 301.42% to 5 ppm NO, accompanied by fast response/recovery times and remarkably low detection limits (0.04 ppb for NO₂ and 0.099 ppb for NO). The device also responds to N₂O, which is chemically stable and resistant to redox reactions, indicating broad sensitivity within the NOX family. Beyond high sensitivity, the sensor boasts superior selectivity toward NOX, strong signal-to-noise ratios, and reliable performance under humid conditions, along with moderate long-term stability. This work not only presents a premier Bi₂S₃-based chemiresistive sensor for room-temperature NOX detection but also validates MOF-derived synthesis as a potent pathway for engineering highly efficient semiconductor gas sensing materials.