Cu-MOF-74-derived Cu₂O/CuO-C nanocomposite as an effective chemiresistive sensor for detection of NO₂ at room temperature

We report a Cu2O/CuO-C nanocomposite which fabricated by thermal decomposition of Cu-based metal-organic framework (Cu-MOF-74) precursor. The attractive advantages of MOF-74 incorporating the abundant unsaturated (open) metal sites and excellent stability provide a guarantee for developing of efficient gas-sensing materials. After annealing, the material retains its skeleton structure and the surface area is greatly increased. The high porosity feature of the as-prepared Cu2O/CuO-C offers plentiful active sites for adsorption of gas molecules, thus ensuring high sensing performance. The results indicate that the Cu2O/CuO-C-based sensor exhibits high sensitivity (1.03-30 ppb NO2), good linear relationship and excellent selectivity to NO2 at room temperature (RT, 25 degree celsius). Notably, the theoretical detection limit of the as-prepared sensor is similar to 7 ppb, which is significantly below the annual average NO2 concentration limit (40 ppm) imposed by China. The synergistic effect between CuO/Cu2O heterostructure and carbon, and the derived solid structure are considered as the main reason for high sensitivity and selectivity. In addition, the high oxygen vacancy concentration is also the key to ensure excellent gas sensitivity. This work provides a new choice for developing high performance room temperature NO2 gas sensor.