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 copper(hexaiminobenzene) (Cu(HIB)) 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 Cu(HIB)-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 NO, HS, SO, NH, CO, as well as CO. Mechanistic investigations of the Cu(HIB)-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.