Pyrazine Functionalization in Eu-MOF for Exclusive Ratiometric Luminescence Sensing of PO<sub>4</sub><sup>3–</sup>
Kun Wu, Xin-Yi Liu, Pei-Wen Cheng, Ji Zheng, Yong‐Liang Huang, Mo Xie, Maolin Liu, Weigang Lu, Dan Li
Abstract
Single-emission luminescence sensors are less than satisfactory for complex systems due to their susceptibility to environmental disturbances. Lanthanum-based metal–organic frameworks (Ln-MOFs) with highly stable ratiometric dual-emission are regarded as promising luminescence probes owing to their fascinating ligand-to-metal energy transfer behaviors (also known as the antenna effect). Herein, we report the synthesis of a pair of isostructural europium-based MOFs (termed JNU-219 and JNU-220 ) by utilizing two X -shaped tetracarboxylate linkers, 4,4′,4″,4‴-benzene-2,3,5,6-tetrayl-tetrabenzoate (BTEB) and 4,4′,4″,4‴-pyrazine-2,3,5,6-tetrayl-tetrabenzoate (BTTB). Both JNU-219 and JNU-220 present the characteristic red luminescence of Eu 3+, yet the pyrazine functionalization of the BTTB linker renders JNU-220 with significantly increased luminescence emission, almost 30 times that of JNU-219 . As a result, the detection limit of JNU-220 for the ratiometric luminescence sensing of PO 4 3– was determined to be as low as 0.22 μM, which is far superior to those of other reported MOF materials. Additionally, we demonstrate the excellent stability and reusability of JNU-220, further verifying its potential as a robust ratiometric luminescence probe.