MIL-88B(Fe)-Derived Fe₂O₃ Hexagonal Spindles for Ultralow Concentration Acetone Detection and Gas-Sensing Mechanism

Metal-organic frameworks (MOFs) have potential applications in gas sensing due to their abundant porosity and unique surface properties. In this study, Fe2O3 hexagonal spindles (Hgs) derived from MIL-88B(Fe) were successfully prepared using an oil bath method, followed by calcination treatment at an optimized temperature of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$450~^{\circ }$ </tex-math></inline-formula>C. The high-purity porous Fe2O3 Hgs showed excellent acetone gas-sensing performance in the range of 0.4–50-ppm acetone concentration. The Fe2O3 Hgs-450 obtained the high sensing response (Ra/Rg =23, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau _{\text {res}} =17$ </tex-math></inline-formula> s, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau _{\text {rec}} =2059$ </tex-math></inline-formula> s), excellent selectivity, and stability over 120 days to 10-ppm acetone at an operating temperature of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$220~^{\circ }$ </tex-math></inline-formula>C. The sensing response value was still 1.88 even at 0.4-ppm acetone and the theoretical detection limit (DL) was calculated to reach 3.59-ppb acetone. These excellent acetone gas-sensing properties were attributed to the uniform porous structure, abundant adsorbed oxygen, and small grain size of Fe2O3 Hgs, making them an excellent candidate for screening diabetic patients through exhaled gas analysis.