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.