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.