Bimetallic MOFs-Derived Metal Oxides Co 3 O 4 /SnO 2 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 Co 3 O 4 /SnO 2 microspheres are prepared by precipitation. Gas-sensing performance shows that the Co 3 O 4 /SnO 2 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 SnO 2 . 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 Co 3 O 4 and SnO 2 , resulting in a greater resistance change of Co 3 O 4 /SnO 2 . Co 3 O 4 /SnO 2 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 Co 3 O 4 /SnO 2 -based sensor is discussed in detail.