Chemiresistive Gas Sensors Based on Ni 3 (HITP) 2 /Ti 3 C 2 Heterojunctions for ppb-Level NH 3 Detection at Room Temperature

In response to the growing demand for efficient NH 3 monitoring in industrial settings, this study reports a novel Ni 3 (HITP) 2 /Ti 3 C 2 hierarchical heterojunction material and fabricated a room-temperature gas sensor based on MEMS technology. Leveraging the high conductivity of Ti 3 C 2 MXene and the porous structure with abundant adsorption sites offered by Ni 3 (HITP) 2 MOF, the composite material exhibits high sensitivity (0.1 ppm), fast response (9 s), and excellent selectivity toward NH 3 at room temperature. Systematic characterization, including SEM, TEM, XRD, XPS, and BET, combined with density functional theory calculations, demonstrated that charge transfer and the built-in electric field at the heterojunction interface significantly enhance gas adsorption and electron transport. The sensor demonstrates robust performance in long-term stability and repeatability tests, offering a promising strategy for developing a new generation of low-power, high-performance gas sensors.