A metal–organic framework as a “turn on” fluorescent sensor for aluminum ions

Abstract

Aluminum ions are harmful to human health and can damage the central nervous system leading to brain cell injury in excessive amounts. Hence, sensing and detection of Al³⁺ ions are important and require a method with high sensitivity and high selectivity. Here, a metal–organic framework {[Zn₂(O-BTC)(4,4′-BPY)_0.5(H₂O)₃]·(H₂O)_1.5·(DMA)_0.5}_n (NUM-2) was constructed by ligands 2-hydroxy-benzene-l,3,5-tricarboxylic acid (HO-H₃BTC) and 4,4′-bipyridine (4,4′-BPY) based upon chain-shaped secondary building units (SBUs). NUM-2 itself exhibits extremely weak fluorescence emission, however, the luminescence intensity of NUM-2 is enhanced obviously when there are Al³⁺ ions in ethanol solutions, and the detection limit calculated using 3σ/k could reach 0.10 ppm, indicating that NUM-2 could be used as an efficient turn-on-based fluorescent sensor with high sensitivity and high selectivity for Al³⁺ ions.