The sensitive detection of formaldehyde in aqueous media using zirconium-based metal organic frameworks

Abstract

The amino derivative of the UiO-66 metal organic framework (MOF) was investigated for potential use as a sensing probe for formaldehyde (FA) in an aqueous medium. The sensitivity and specificity of this MOF probe were virtually unaffected by the presence of other tested reference aldehydes, e.g., propionaldehyde( PA), butyraldehyde (BA), and valeraldehyde (VA). The maximum incubation time for the interaction of the MOF probe against 100 ppm of FA standard was estimated at 2 min. The linear detection of FA molecules using the proposed probe was performed in the range of 10-100 ppm with a limit of detection (LOD) at 4 ppm. The stability of the MOF for FA detection was estimated through a series of adsorption-desorption cycles. DFT calculations showed that the selective sensing/capture of FA corresponded to the formation of a stable, non-covalent bond between FA and the C6H3NH2 unit of the MOF. This interaction decreased the HOMO/LUMO gap of FA by approximately 0.8 eV, a trend that was not evident for all other aldehydes. The results of FTIR, TGA, and XPS analysis confirmed a small but visible change in the chemical environment of the N-H and C-H bonds of UiO-66-NH2 upon their interactions with FA molecules. Therefore, the proposed MOF probe appears suitable for sensing FA in an aqueous medium.