Tannic acid (TA)-assisted fabrication of 1D hollow In2O3@Fe2O3 core-shell tubes for humidity-tolerant acetone detection

Reliable detection of volatile organic compounds (VOCs), such as acetone, is essential for environmental monitoring and non-invasive disease diagnosis. However, conventional In 2 O 3 -based gas sensors suffer from high operating temperatures, humidity interference, and limited selectivity. Herein, we report one-dimensional (1D) hollow In 2 O 3 @Fe 2 O 3 core-shell heterojunction tubes fabricated via a tannic acid (TA)-assisted transformation of MIL-68(In). TA plays dual roles in etching the MIL-68(In) template and coordinating with Fe 3+ ions to form a mesoporous tubular structure with an enhanced specific surface area of 89.57 m 2 g -1 for In 2 O 3 @Fe 2 O 3 -0.75. Benefiting from the synergistic n-n heterojunction effect and abundant active sites, the optimized In 2 O 3 @Fe 2 O 3 -0.75 sensor exhibits a markedly improved response of 263.6 to 100 ppm acetone at 200 °C, approximately 3.6 times that of pristine In 2 O 3 , and enables detection down to 100 ppb with a response of 1.87. Furthermore, the sensor demonstrates rapid response/recovery (8/9 s), excellent long-term stability over 30 days, and remarkable humidity tolerance across 29-82% RH at 25 °C. This work provides an effective MOF-derived strategy for constructing hollow metal-oxide core-shell heterojunctions toward high-performance and humidity-tolerant gas sensing applications. • 1D In 2 O 3 @Fe 2 O 3 core-shell tubes were fabricated with the assistance of TA. • TA acts as both an etchant for MIL-68(In) template and a complexing agent. • In 2 O 3 @Fe 2 O 3 -0.75 sensor demonstrates response of 263.6 to 100 ppm acetone. • The In 2 O 3 @Fe 2 O 3 -0.75 sensor achieves outstanding humidity resistance. • The enhanced performance is ascribed to two components and synergistic effects.