Bimetallic MOFs-Derived Metal Oxides Co₃O₄/SnO₂ Microspheres for Ultrahigh Response n-Butanol Gas Sensors

The construction of p-n heterojunctions is expected to be one of the effective means to improve gas sensitivity. In this research, p-n heterojunctions are successfully constructed by metal oxides derived from metal-organic frameworks (MOFs). MOFs-derived bimetallic Co₃O₄/SnO₂ microspheres are prepared by precipitation. Gas-sensing performance shows that the Co₃O₄/SnO₂ sensor exhibits an extremely high response (R_a/R_g = 641) to 20 ppm of n-butanol at 200 °C, which is 19 times that of pristine SnO₂. It can detect n-butanol gas at low concentrations, has good selectivity to alcohol gas, and reduces the interference of benzene gas. The improved gas sensitivity can be attributed to the formation of a stable heterojunction between Co₃O₄ and SnO₂, resulting in a greater resistance change of Co₃O₄/SnO₂. Co₃O₄/SnO₂ inherits the characteristic of high specific surface area of MOFs, which provides abundant sites for the reaction of the target gas and oxygen molecules. Finally, the gas-sensing mechanism of the Co₃O₄/SnO₂-based sensor is discussed in detail.