MOF-Derived Mesoporous and Hierarchical Hollow-Structured In2O3-NiO Composites for Enhanced Triethylamine Sensing

It remains a challenge to design and fabricate high-performance gas sensors using metal–organic framework (MOF)-derived metal oxide semiconductors (MOS) as sensing materials due to the structural damage during the annealing process. In this study, the mesoporous In2O3-NiO hollow spheres consisting of nanosheets were prepared via a solvothermal reaction and subsequent cation exchange. More importantly, the transformation of Ni-MOF into In/Ni-MOF through exchanging the Ni2+ ion with In3+ ion can prevent the destruction of the porous reticular skeleton and hierarchical structure of Ni-MOF during calcination. Thus, the mesoporous In2O3-NiO hollow composites possess high porosity and large specific surface area (55.5 m2 g–1), which can produce sufficient permeability pathways for volatile organic compound (VOCs) molecules, maximize the active sites, and enhance the capacity of VOC capture. The mesoporous In2O3-NiO-based sensors exhibit enhanced triethylamine (TEA) sensing performance (S = 33.9–100 ppm) with distinct selectivity, good long-term stability, and lower detection limit (500 ppb) at 200 °C. These results can be attributed to the mesoporous hollow hierarchical structure and p–n junction of In2O3-NiO. The preparation concept mentioned in this work may provide a versatile platform applicable to various mesoporous composite sensing material-based hollow structures.