An international team of researchers, led by scientists from the University of Manchester, has successfully developed a metal-organic framework (MOF) material that can capture nitrogen dioxide (NO2), a toxic air pollutant resulting from the use of diesel and bio-fuel, converting it into nitric acid, a valuable chemical primarily used in agricultural fertilizers, nylon, and rocket propellant. The researchers employed neutron scattering and synchrotron X-ray diffraction at the Department of Energy’s Oak Ridge National Laboratory and Berkeley National Laboratory, respectively, while making the MOF. The National Service for Electron Paramagnetic Resonance Spectroscopy at Manchester was also applied to understand the underlying mechanism of the adsorption of NO2 in the new material, named MFM-520. The team’s work has been described in the journal Nature Chemistry.
The newly-developed technology might aid air pollution control and help reduce the negative impact of the chemical on the environment. MFM-520 can capture NO2 at ambient temperatures and pressures, even during flow and at low concentrations, with sufficient moisture, carbon dioxide, and sulfur dioxide in its surroundings. Even though the pollutant is highly reactive, the material was able to undergo complete regeneration several times through degassing or upon being treated with water in the air, a process that can also be used to convert nitrogen dioxide into nitric acid. The lead author of the study, Dr. Sihai Yang, Senior Lecturer, Department of Chemistry, the University of Manchester, says that the material is the first MOF that has been able to both capture and turn a toxic and gaseous air pollutant into a valuable compound for industrial use, adding that the highest rate of NO2 uptake by this MOF happens at approximately 45 degrees Centigrade, which is nearly the temperature of automobile exhausts.
For the study, the team used neutron spectroscopy and computational techniques at Oak Ridge National Laboratory to accurately decipher the way that the material captures NO2 molecules. A lead author of the study, Martin Schröder, Professor and Vice-President and Dean, Faculty of Science and Engineering, the University of Manchester, says that the Global Nitric Acid Market was valued at about $2.5 billion in 2016. This will create a massive potential for producers of their MOF technology to recover the cost and profit of the resulting nitric acid production, mainly because the additives required in the process are only water and air, adds Professor Schröder.