High-performance ammonia sensor at room temperature based on 2D conductive MOF Cu₃(HITP)₂

Sensitive detection of ammonia in the environment is crucial due to its potential danger to human ecology and health. In gas detection technology, resistive sensors utilizing golden cross finger electrodes combined with gas-sensitive materials are commonly employed. In this study, we demonstrated a room-temperature sensor for ambient ammonia detection. The sensor is composed of two-dimensional layer-stacked metal-organic framework (MOF) Cu₃(HITP)₂ nanomaterials drop-coated onto gold-forked finger electrodes. Density-functional theory simulation (DFT) and sensor gas-sensitive performance testing were conducted for characterization. The sensor exhibited high sensitivity, selectivity, low detection limit, excellent reproducibility, and stability. This can be attributed to the abundant Cu active sites exposed in the hexagonal ring and layer-stacked framework structure of Cu₃(HITP)₂ nanomaterials. Ammonia adsorption leads to electron transfer into the Cu₃(HITP)₂ framework, resulting in decreased sensor resistance. Real-time monitoring of sensor resistance changes enabled quantitative analysis. Results showed a 91.4 % response of the Cu₃(HITP)₂ sensor to 100 ppm NH₃, with response and recovery times of 26 s and 20 s, respectively. The sensor's limit of detection (LOD) was approximately 15 ppb. The sensor exhibited a relatively high response to NH₃ at 25 °C, as demonstrated by dynamic gradient test curves. These findings suggest that constituting a room-temperature ammonia sensor by uniformly drop-coating Cu₃(HITP)₂ onto a gold-forked finger electrode is a feasible strategy.