Hybrid 2D MoS2–Copper Benzene-1,3,5-Tricarboxylate Framework for Room-Temperature Gas Sensing: Toward Trace Ammonia Detection for Hydrogen-Carrier Safety

Room-temperature detection of trace ammonia (NH3) is essential for hydrogen-carrier safety, yet achieving high sensitivity and analyte discrimination remains challenging. Here, three metal–organic frameworks (CuBTC, ZIF-8, and UiO-66) were hybridised with two-dimensional MoS2 and comparatively evaluated for room-temperature chemoresistive sensing of NH3 and selected volatile organic compounds (VOCs). Among these hybrids, CuBTC–MoS2 exhibited the highest and most reproducible NH3 response, reaching approximately 35% at 0.8 ppm, with a calculated limit of detection (LOD) of 0.013 ppm (13 ppb). The sensor demonstrated a superior response toward NH3 than other investigated gases, including formaldehyde, especially at concentrations of 0.8–10 ppm, whereas formaldehyde produced a stronger response above approximately 17 ppm. Rapid response and recovery times of 6 s and 9 s, respectively, were achieved. The enhanced NH3 response is attributed to favourable adsorption within CuBTC and interfacial charge modulation in the CuBTC–MoS2 hybrid. These findings highlight the potential of CuBTC–MoS2 for trace NH3 monitoring in hydrogen-carrier systems while identifying concentration-dependent cross-sensitivity as a consideration for practical applications.