<p>Low-concentration acetone detection is of great importance for acetone sensor in the fields of environmental protection and noninvasive diagnosis. In this work, mesoporous Fe₂O₃/Cr₂O₃ n-p heterojunctions were constructed for efficient improvement of low-concentration acetone gas sensing. The gas-sensing results indicated that the mesoporous Fe₂O₃/Cr₂O₃ composites with a significantly large specific surface area exhibited significantly enhanced acetone gas-sensitive performance compared to pure Fe₂O₃. The Fe₂O₃/Cr₂O₃ composites demonstrated a high response, good selectivity and excellent stability over 200&#xa0;days to 10&#xa0;ppm acetone at 220&#xa0;°C. And the theoretical detection limit was calculated to reach 0.285&#xa0;ppm acetone. A feasible acetone sensing mechanism was proposed through electronic band structure and density functional theory. The improved low-concentration acetone sensing performance was due to the formed mesoporous Fe₂O₃/Cr₂O₃ n-p heterojunctions with a large specific surface area. The Fe₂O₃/Cr₂O₃ composites showed excellent acetone gas-sensitive performance, which could be a promising candidate for developing low-concentration acetone sensing devices at low working temperatures.</p> Graphical abstract <p></p>