Hydrolytically Stable Luminescent Cationic Metal Organic Framework for Highly Sensitive and Selective Sensing of Chromate Anions in Natural Water Systems

Abstract

Effective detection of chromate anions in aqueous solution is highly desirable because of their high solubility, environmental mobility, carcinogenicity, and bioaccumulation effect. A new strategy for precise detection of chromate anions in the presence of a large excess of other anions, such as Cl, NO, and HCO, in drinking water and natural water systems remains a challenge. Herein, a hydrolytically stable cationic luminescent europium(III)-based metal organic framework (MOF), 1, was successfully synthesized and investigated as a luminescent sensor that exhibits instant and selective luminescence quenching properties toward chromate ions in aqueous solutions. Moreover, 1 can be introduced into high-ionic-strength water system (e.g., seawater) for chromate detection as a consequence of the excellent sensing selectivity. The real environmental application of 1 as a chromate probe is studied in deionized water, lake water, and seawater. The detection limits in these aqueous media are calculated to be 0.56, 2.88, and 1.75 ppb, respectively. All of these values are far below the maximum contamination standard of Cr(VI) in drinking water of 100 ppb, defined by the U.S. Environmental Protection Agency. This excellent chromate sensing capability originates from the fast enrichment of chromate ions in solids of 1 from solutions, followed by efficient energy transfer from the MOF skeleton to the chromate anion, as demonstrated by solution absorption spectroscopy, X-ray diffraction, and chromate uptake kinetics and isotherm investigations. To the best of our knowledge, 1 possesses the lowest chromate detection limit among all reported MOFs up to date and is the only MOF material reported for chromate sensing application under environmentally relevant conditions with high ionic strengths.

An Ultrafast Molecular‐Rotor‐Based Fluorescent Turn‐On Sensor for the Perrhenate Anion in Aqueous Solution

“…Note that the iodide anion leads to quenching of the ThT emission, which can be attributed to its very‐well‐known heavy‐atom effect. In addition to these anions, natural water also contains various metal cations that may affect the fluorescence properties of ThT. Thus, we have also evaluated the response of ThT towards various environmentally abundant cations such as Na + , Ca 2+ , Zn 2+ , Mg 2+ , Cu 2+ , Sr 2+ , and Al 3+ , none of which led to any significant increase in ThT fluorescence (see Figure S6 in the Supporting Information).…”

Design and Synthesis of Fluorescent Nanocelluloses for Sensing and Bioimaging Applications

“…The massive discharge of heavy metals and toxic metal ions is the direct cause of much wastewater pollution. Cr(VI) ions, as the most abundant heavy metal ions in wastewater, have a strong carcinogenic effect and destroy the human respiratory, digestive, and immune systems . Bhagat et al.…”

“…Cr(VI) ions, as the most abundant heavy metal ions in wastewater, have a strong carcinogenic effect and destroy the human respiratory, digestive, and immune systems. [76,77] Bhagat et al have developed a new multifunctional chemical used for naked-eye sensing, rapid adsorption, and as an antibacterial agent by virtue of 2-aminoethane-1-sulfonic acid and mercaptopropionic acid (MPA) modifying spherical NCs (SNCs). Compared with the original cellulose, these spherical NCs show a stronger adsorption affinity for heavy metal ions.…”

Functionalization of Metal–Organic Frameworks for Photoactive Materials

“…Moreover, compared to amorphous materials, the highly ordered crystalline nature of MOFs allows for precise structural determinations and specific knowledge of structural changes that occur during the detection of an analyte and the detail sensing mechanism. To date, a wide range of luminescent MOFs, particularly lanthanide‐based MOFs, have been realized and reported as sensors for ions, small molecules, gas/vapors, temperature, pH values, and moisture …”