In situ generation of cuprous oxide in metal-organic framework for significantly enhanced room-temperature ammonia sensing: Synergy enabling excellent sensitivity and selectivity

Development of effective strategies to improve the response sensitivity of metal-organic frameworks (MOFs) to target gases is imperative to further enhancing their application potential in gas sensing. In this work, series of CuHHTP/Cu 2 O (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) composites are successfully constructed by in-situ electrochemical reduction treatment of CuHHTP, and the changing trend of first increasing and then decreasing with increase of CuHHTP electrochemical reduction degree for their sensitivity to NH 3 detection is revealed. When the average size of Cu 2 O nanoparticles generated in CuHHTP is 3.6 nm, the corresponding CuHHTP/Cu 2 O-A composite exhibits the best NH 3 sensing performance compared to pristine CuHHTP, including significantly enhanced response sensitivity, ultralow experimental detection limit of 10 ppb, superior selectivity, good reproducibility, and excellent response stability even after placed for 90 days. More impressively, thanks to integration and synergy of the uniformly-dispersed small-sized Cu 2 O nanoparticles with significantly enhanced adsorption activity and capacity for NH 3 , the released large amount of uncoordinated hydroxyl groups that can interact with NH 3 , as well as the active sites of the CuHHTP substrate itself, the 10 ppb experimental detection limit for the CuHHTP/Cu 2 O-A-based sensors is not only the lowest one reported in the past 10 years for NH 3 sensors based on copper-containing MOF and oxide materials, but also superior to that of 0.1–1 ppm for the existing commercial NH 3 sensors. This work opens the avenue for design and development of novel MOF-based sensing materials.