A 2D Zn-MOF as an Efficient Luminescent Sensor for Detecting Cr2O72− in Water Media and HEPES Biological Buffer Solution

Efficient detection of toxic heavy metal anions Cr₂O₇²⁻ residue in water media is of great significance due to its severe damage to ecosystem and human health. Herein, a new 2D (two-dimensional) luminescent metal–organic frameworks (MOFs) {[Zn₂(bmida)(phen)]·H₂O}_n (abbr.Zn-MOF) (1,10-phen = 1,10-phenanthroline, H₄bmida = N-(phosphonomethyl)iminodiacetic acid) was constructed and structurally characterized. Notably, this Zn-MOF as an efficient luminescent sensor can detect Cr₂O₇²⁻ both in water media and HEPES biological buffer solution with high selectivity and sensitivity, and good cyclic stability. The corresponding detection limit (LOD) of Zn-MOF towards Cr₂O₇²⁻ is as low as 1.21 and 5.46 µM with large quenching constant (K_sv), respectively. The LOD in H₂O solution is lower than the benchmark of drinking water recommended by United States Environmental Protection Agency (USEPA, 1.92 µM). Moreover, a possible competitive energy absorption mechanism is suggested by multiple experiments.