Selective and Sensitive Detection of Formaldehyde by ZIF-90-LW via Aza-Cope Rearrangement

Formaldehyde (FA), as one of the simplest reactive carbonyl species (RCS), is more widely known as an environmental toxin and carcinogen. In this work, a new ZIF-90 type material (ZIF-90-LW) was synthesized and investigated, of which combined two strategies of “2-aza-Cope rearrangement” and “MOFs structure” by the combination of the pre-functionalized 2-allylaminoimidazole ligand and Zn2+ salt under solvothermal conditions. From this, the hurdle in selectivity of other carbonyl compounds (RCS) would be averted even though their similar electrophilic reactivities as FA, and a prominent fluorescence turn-on type signaling was realized by the 2-aza-Cope rearrangement mechanism. A good linear relationship (R2 = 0.9943) was obtained by fitting the fluorescence intensity towards FA from 0 to 25 mM, and the detection limit of ZIF-90-LW to FA was 0.67 ppM. In addition, it also showed potentially useful sensing ability for the detection of FA in both liquid and gas phase, and might therefore be used to rapidly dectet FA in a response time of 28 s in liquid phase, while 20 s in gas phase. All the above features clearly demonstrate that ZIF-90-LW has the great potential to sensitive and selective recognize FA in the environment.