Water Stable Metal–Organic Framework Based on Phosphono-containing Ligand as Highly Sensitive Luminescent Sensor toward Metal Ions

Abstract

Metal–organic frameworks (MOFs)-based fluorescent sensors have attracted much attention due to their high selectivity, sensitivity, and operability. However, the poor stability of MOFs seriously limits their applications in detecting toxic species in water system. Herein, taking advantage of the high chemical stability of the metal phosphonate bond, the easy crystallinity of carboxylate, and the π-conjugated benzene, a new luminescent MOF with three-dimensional network has been successfully synthesized using the predesigned 5-phosphonobenzene-1,3-dicarboxylic acid (H4pbdc) ligand. [Cd2(pbdc)(H2O)3] (1) not only possesses excellent stability in water and some organic solvents but also can remain structural integrity in acidic/alkaline aqueous solutions with pH value ranging from 4 to 10. Remarkably, 1 can efficiently and sensitively probe Cu2+, Al3+, and Fe3+ ions over other metal ions in an aqueous system. The quenching constant of Ksv and detection limit are 1.57 × 106 M–1 and 38.9 nM for Cu2+ ions, 2.86 × 105 M–1 and 139.0 nM for Al3+ ions, and 1.86 × 105 M–1 and 167.6 nM for Fe3+ ions, respectively. This work proposes a feasible strategy for constructing stable MOFs as highly sensitive luminescent sensors in water system.