MOF-derived synthesis of mesoporous In/Ga oxides and their ultra-sensitive ethanol-sensing properties

Abstract

A series of In/Ga-based MIL-68s, with batch molar ratios of In(III) to Ga(III) (In/Ga ratio) equaling 5 : 0, 4 : 1, 3 : 2, 1 : 1, 2 : 3, 1 : 4, and 0 : 5, were solvothermally prepared. Calcinating the as-prepared MOFs at 500 °C for 3 h produced a series of mesoporous In/Ga oxides (IGOs) of hexagonal morphology with a characteristic main pore radius of 3 nm to 12 nm, and a specific surface area of up to 60–135 m² g⁻¹. Studies on the ethanol gas-sensing properties of the as-prepared IGOs revealed that the two IGOs produced from MIL-68 with In/Ga ratios of 3 : 2 and 1 : 1 present high response values of 80–110 towards 300 ppm ethanol and a low detection limit of no more than 2 ppm. However, the response value of In₂O₃, produced from MIL-68 with an In/Ga ratio of 5 : 0, was 11 towards 300 ppm ethanol. At the same time, the two IGO samples exhibited a high response to ethanol, which was more than 2.6 times higher than response values towards CH₃CHO, CH₃COCH₃, H₂, CO, CH₄, and NO₂, at a concentration of 300 ppm. This gas-sensing performance is suggested to be attributed to their comparatively larger specific surface area, and remarkable oxygen vacancy capabilities.