Response and Selectivity of α-Fe₂O₃@ZIF-71 Nanoneedles for NO₂ Sensing

α-Fe2O3@ZIF-71 nanomaterials, with an average width of 100 nm, were synthesized on Al2O3 ceramic tubes via a two-step hydrothermal method. The ZIF-71 ligands were modified via a secondary hydrothermal treatment. Gas-sensing experiments demonstrated that the modified α-Fe2O3@ZIF-71(NBIM) exhibited enhanced selectivity and sensing response toward NO2. At 220 °C, its response to 10 ppm of NO2 was 17.20, which is 1.9 times that of pristine α-Fe2O3 and 1.4 times that of unmodified α-Fe2O3@ZIF-71. When triethylamine was the interfering gas, the material’s selectivity was 1.5 times that of α-Fe2O3@ZIF-71 and 3.3 times that of α-Fe2O3. With NO as the interfering gas, α-Fe2O3@ZIF-71(NBIM)’s selectivity was 1.2 times that of α-Fe2O3@ZIF-71 and 1.4 times that of α-Fe2O3. Meanwhile, the grand canonical Monte Carlo (GCMC) method was employed to investigate the sieving effects of four types of ZIF-71 with different pendant groups. On the other hand, density functional theory (DFT) was utilized to analyze the adsorption mechanisms of NO2 on α-Fe2O3 and α-Fe2O3@ZIF-71(NBIM) nanomaterials. The DFT analysis results were in good agreement with the experimental results. The findings indicated that α-Fe2O3@ZIF-71(NBIM) enhanced the selectivity and response value of metal oxide gas sensors, providing an approach to improve the selectivity and response value of metal oxide gas sensors.