Mixed-Solvent-Regulated MOF-Derived Porous In₂O₃ Nanostructures for Enhanced Triethylamine Gas Sensing

The detection of triethylamine (TEA) at low concentrations requires sensing materials with high surface reactivity and efficient gas-transport capability. In this work, porous In₂O₃ nanostructures were successfully prepared through a mixed-solvent-regulated metal-organic framework-derived (MOF) strategy. Indium nitrate and terephthalic acid were used as the metal source and organic ligand, respectively. By adjusting the volume ratio of N,N-dimethylformamide and ethanol, the nucleation and growth of In-based MOF precursors were effectively regulated, followed by thermal conversion into porous MOF-derived In₂O₃ materials. Structural characterization confirms that all samples were completely transformed into cubic In₂O₃ after calcination and exhibited porous architectures assembled from In₂O₃ nanoparticles. The solvent composition was found to exert a pronounced influence on the pore structure, defect concentration, and surface oxygen species. Gas-sensing measurements reveal that the MOF-In₂O₃ sensor delivered the best TEA-sensing performance at 240 °C, with a response of 77 toward 100 ppm TEA, relatively fast response/recovery behavior, a detection limit down to 0.5 ppm, and good selectivity and long-term stability. The superior performance can be attributed to the continuous gas-diffusion channels constructed by nanoparticle assembly, abundant oxygen vacancies and chemisorbed oxygen species that promote surface oxidation reactions, and the effective catalytic oxidation capability of In₂O₃ toward TEA molecules. This study demonstrates that regulating the solvent composition during MOF precursor synthesis is a simple and effective route to optimize the microstructure and surface defects of In₂O₃ for improved TEA gas sensing.