Semiconductor oxide gas sensors have important applications in environmental protection, domestic health, and other fields. Research has shown that designing the morphology of sensitive materials can effectively improve the sensing characteristics of sensors. In this paper, by controlling the solvothermal reaction time, a unique hexagonal flower-like structure of In₂O₃ materials consisting of cuboid nanorods with a side length of 100–300 nm was prepared. The characterization results indicated that with the increase in reaction time, the materials exhibited significant morphological evolution. When the solvent heating time is 5 h, the flower-like structure is basically composed of hexagonal nanosheets with a thickness of several hundred nanometers and a side length of several micrometers. With the increase in reaction time, the apex angles of the nano sheets gradually become obtuse, and, finally, with the Ostwald ripening process, they become cuboid nanorods with side lengths of 100–300 nanometers, forming unique micro-flowers. Among them, the material prepared with a reaction time of 20 h has good sensing performance for NO₂, exhibiting low operating temperature and detection limit, good selectivity, repeatability, and long-term stability, thus suggesting a good application prospect.

Triethylamine (TEA), a widely used volatile organic compound (VOC), poses severe threats to environmental safety and human health upon accidental leakage, making the development of high-performance TEA detection techniques urgently needed. Herein, we report a Sn-based metal–organic framework (Sn-MOF) constructed from 4,5-dichloroimidazole ligands synthesized via a solvothermal approach. The resulting MOF-derived SnO₂ materials were obtained by calcination at 400–600 °C, yielding SnO₂ with tunable specific surface area and surface defect-site density. Structural and surface characterizations revealed that the materials consist of primary nanoparticles in the range of 10–50 nm, forming aggregated particles of 1–2 µm. The gas sensing performance toward TEA was systematically evaluated. The SnO₂-400 °C sensor exhibited the highest response (S = 85.0) to 100 ppm TEA at 190 °C, with a low detection limit of 1 ppm, superior selectivity, good repeatability, and excellent long-term stability. The observed performance variation was attributed to the combined effects of specific surface area, abundant defect-associated surface sites, and suitable mesoporous structure. This work not only provides a high-performance TEA sensor for industrial and food safety monitoring but also offers a rational strategy for designing MOF-derived metal oxide gas sensors with tailored microstructures and surface defect chemistry.