Reversible and Ultrasensitive Detection of Nitric Oxide Using a Conductive Two-Dimensional Metal-Organic Framework

This paper describes the use of a highly crystalline conductive 2D copper₃(hexaiminobenzene)₂ (Cu₃(HIB)₂) as an ultrasensitive (limit of detection of 1.8 part-per-billion), highly selective, reversible, and low power chemiresistive sensor for nitric oxide (NO) at room temperature. The Cu₃(HIB)₂-based sensors retain their sensing performance in the presence of humidity, and exhibit strong signal enhancement towards NO over other highly toxic reactive gases, such as NO₂, H₂S, SO₂, NH₃, CO, as well as CO₂. Mechanistic investigations of the Cu₃(HIB)₂-NO interaction through spectroscopic analyses and density functional theory revealed that the Cu-bis(iminobenzosemiquinoid) moieties serve as the binding sites for NO sensing, while the Ni-bis(iminobenzosemiquinoid) MOF analog shows no noticeable response to NO. Overall, these findings provide a significant advance in the development of crystalline metal-bis(iminobenzosemiquinoid)-based conductive 2D MOFs as highly sensitive, selective, and reversible sensing materials for the low-power detection of toxic gases.