Bismuth Molybdate Nanorods Derived from a Metal–Organic Framework for Triethylamine Gas Sensors

A heterojunction metal oxide semiconductor made of three phases of bismuth molybdate (BMO) (α, β, γ) was synthesized by a one-pot process from a metal–organic framework (MOF) and evaluated in a side-heated sensor for the detection of the toxic gas triethylamine (TEA). An X-ray diffraction analysis indicated that the heterostructure comprises 24.1% α-Bi2Mo3O12, 59.1% β-Bi2Mo2O9, and 16.8% γ-Bi2MoO6. Because of the collapse of the MOF structure during the synthesis process, BMO nanorods exhibited surface defects beneficial for gas sensing. Consequently, the TEA sensing performance of αβγ-BMOMOF was significantly superior to αβγ-BMO prepared instead with uncoordinated bismuth nitrate. When compared to single-phase α-Bi2Mo3O12MOF and γ-Bi2MoO6MOF sensors, the αβγ-BMOMOF heterojunction sensor exhibited high performance with a limit of detection of 0.5 ppm and a response value of 58.5 to 100 ppm TEA at an optimal temperature of 340 °C. In addition, αβγ-BMOMOF nanorods exhibited excellent selectivity, long-term stability, and short response and recovery times of 2 and 5 s, respectively. Because of heterojunctions between the different phases, the αβγ-BMOMOF sensor had a higher electrical resistance in air and adsorbed a larger quantity of oxygen anions capable of reacting with TEA. These features of the heterostructure material explain its superior TEA sensing performance. The low-cost and low-toxicity αβγ-BMOMOF sensor described here is a promising alternative for the detection of volatile organic molecules.