Amino group dependent sensing properties of metal–organic frameworks: selective turn-on fluorescence detection of lysine and arginine

Abstract

Recently, metal–organic frameworks (MOFs) have been extensively investigated as fluorescence chemsensors due to their tunable porosity, framework structure and photoluminescence properties. In this paper, a well-known Zr(IV)-based MOF, UiO-66-NH₂ was demonstrated to have capability for detection of L-lysine (Lys) and L-arginine (Arg) selectively from common essential amino acids in aqueous media via a fluorescence turn-on mechanism. Further investigation reveals its high sensitivity and strong anti-interference properties. Moreover, the possible mechanism for sensing Lys and Arg was explored by FT-IR and ¹H-NMR, and the results indicate that the enhancement of the fluorescence could be ascribed to the adsorption of Lys/Arg and the hydrogen bonding interactions between Lys/Arg and the amino group of UiO-66-NH₂. The difference of the sensing capacity and sensitivity between UiO-66 and UiO-66-NH₂ revealed that the amino group plays an essential role in the sensing performance. This work presents a unique example of the functional group dependent sensing properties of MOFs.