Porous crystals detect nitric oxide
The detection of nitric oxide (NO) is important for monitoring air quality because NO released during the burning of fossil fuels causes acid rain and smog. Medically, NO is an important messenger molecule that serves as a biomarker for asthma. in diary applied chemistrya research team now reports a material that can reversibly detect NO with low power, high sensitivity, and selectivity: a copper-containing, conductive, two-dimensional metal-organic framework.
Metal-organic frameworks (MOFs) are lattice structures composed of metal “nodes” connected by organic bridges (ligands). An emerging class of MOFs are conductive structures composed of layers. These 2D-cMOFs have shown great potential as chemical resistance sensors, where they respond to the presence of specific molecules and change their resistance, which may allow particularly sensitive and low-power detection of toxic gases. Problems with such systems include cross-reactivity with multiple gases and limited reusability due to irreversible binding of analytes.
Katherine A. Mirica, Christopher H. Hendon and their teams from Dartmouth College (Hanover, NH, USA), University of Oregon (Eugene, OR/USA), and Ulsan National Institute of Science and Technology (South Korea), A reusable 2D-cMOF has now been developed for highly selective detection of NO. They chose to use 2D-cMOF based on copper and heximinobenzene, Cu3(HIB)2. Due to their different synthesis strategies (the linker is added to the Cu solution as an insoluble powder)2+ ions and potassium acetate), the team produced a material that was significantly more crystalline than previous materials (rod-shaped crystallites about 500 nm in length).
The microcrystals consist of stacked layers of a network of six-membered rings linked together by copper ions bound to their nitrogen atoms. Spectral analysis and calculations indicate that the binding site for NO is the Cu-bis(iminobenzosemiquinone) unit of copper-2D-cMOF. Similar compounds made with nickel instead of copper did not absorb NO significantly. Obviously, in addition to the doubly positively charged copper ions, the small amount of singly positively charged copper ions present in the structure plays an important role in binding NO. Computational studies show that adsorbed NO will significantly distort the structure and destabilize the bound state, which is the main reason for the ideal reversibility of NO adsorption.
This new sensor material can detect NO with high sensitivity (detection limit approximately 1.8 ppb) at room temperature and low voltage (0.1 V), and can be reused for at least seven cycles without regeneration. Quantitative measurement of NO is also successful in the presence of moisture, the sensor signal of which is highly enhanced compared to other gases such as nitrogen dioxide, hydrogen sulfide, sulfur dioxide, ammonia, carbon monoxide and carbon dioxide.
2024-12-12 17:02:21