Highly sensitive and selective fluorescence detection of hypochlorite by amorphous europium metal-organic frameworks with dual ligands

Hypochlorite (ClO − ) is the most commonly used disinfectant on various occasions, the development of high-performance approaches for the reliable determination of hypochlorite is of great significance in human health and public safety. Moreover, visually analyzing ClO − in the water environment is more convenient. The ratiometric fluorescent approach based on lanthanide-based metal-organic frameworks is an effective way for the detection of ClO − . In this approach, an amorphous europium metal-organic framework with dual ligands was applied to detect ClO − . Amorphous dual-ligand europium-organic frameworks were prepared by using Eu 3+ as metal nodes, 2-aminoterephthalic acid (NH 2 BDC) and enoxacin (ENX) as dual ligands (denoted as amEu-ENX/NH 2 BDC). The amEu-ENX/NH 2 BDC displayed a dual emission derived from NH 2 BDC and Eu 3+ at 427 and 611 nm, respectively. In the presence of ClO − , static quenching weakened the blue fluorescence at 427 nm, while the antenna effect emission from Eu 3+ kept stable, thus a ratiometric fluorescent detection of ClO − was realized with a fast response time of less than 40 s. The synthesized amEu-ENX/NH 2 BDC presented a great detection performance for ClO − with a wider linear concentration range from 0.50 to 15 μM and 15–40 μM. The detection limit was 30 nM (3 σ /k = 3). The color changes of amEu-ENX/NH 2 BDC enabled the concentration of ClO − to be detected by smartphone conversion of RGB. Importantly, the proposed fluorescence sensor can successfully monitor ClO − in real samples.