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 NH3 monitoring in industrial settings, this study reports a novel Ni3(HITP)2/Ti3C2 hierarchical heterojunction material and fabricated a room-temperature gas sensor based on MEMS technology. Leveraging the high conductivity of Ti3C2 MXene and the porous structure with abundant adsorption sites offered by Ni3(HITP)2 MOF, the composite material exhibits high sensitivity (0.1 ppm), fast response (9 s), and excellent selectivity toward NH3 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.