In2O3/ZnO S-scheme heterojunction nanocomposite hollow microtubes with highly sensitive response to formaldehyde

As we all know, formaldehyde (HCHO) is extremely harmful to human health and has been identified as a primary carcinogen by the World Health Organization. Therefore, there is an urgent need to design efficient formaldehyde-sensing materials. In this work, a highly responsive formaldehyde sensor of In2O3@ZnO derived from MIL-68(In)@ZIF-8 precursor was successfully prepared. By adjusting the ratio of In2O3 and ZnO, it can be found that the performance of the resulting sensor has greatly improved under 100 ppm HCHO at an operating temperature of 220 °C and the detection limit can be as low as 4 ppb. Additionally, it also has excellent selectivity (Q≥10), anti-interference (the deviation value≤3.5%), and long-lasting stability (the variation value≤4%). Such distinguished sensing performance can be attributed to the metal-organic framework (MOF) derived step-scheme (S-scheme) heterojunction, which ultimately increases the adsorption of oxygen and HCHO. This work verifies that ingenious heterojunction construction can significantly improve gas sensing performance.