Zinc metal–organic framework with 3-pyridinecarboxaldehyde and trimesic acid as co-ligands for selective detection of Cr (VI) ions in aqueous solution

Abstract

There is an increasing need for the development of probes for the detection of hexavalent chromium since it is a known carcinogen, which can cause adverse effects on human health. Metal-organic frameworks (MOFs) have shown successful detection and removal of hazardous substances from aqueous media. This work presents the use of simple organic ligands such as 3-pyridinecarboxaldehyde and trimesic acid with Zn(II) ion to fabricate a new MOF that exhibits sensitive and selective luminescence quenching response towards CrO4 2− and Cr2O7 2− species in aqueous solution. The MOF showed a detection limit of 0.67 μM (0.078 ppm) as CrO4 2− species and 1.91 μM (0.41 ppm) as Cr2O7 2− species. Results reveal that the as-synthesized MOF could serve as a good luminescent sensor for CrO4 2− and Cr2O7 2− species in the contaminated aqueous phase.

N,Zn-Doped Fluorescent Sensor Based on Carbon Dots for the Subnanomolar Detection of Soluble Cr(VI) Ions

“…The -CN peaks [ 26 , 40 , 41 ] at 2356, 1408, and 1079 cm −1 are the stretching vibrations of the pyridyl nitrogen, indicating that 4-pyridinecarboxaldehyde was fully involved in the formation of the nanomaterial. The peaks at 1697, 1213, 1079, and 1027 cm −1 are assigned to the C=O stretching vibrations of the aromatic rings in 4-pyridinecarboxaldehyde and the carboxyl group in citric acid [ 34 ]. The peak at 1339 cm −1 is attributed to the -CHO out-of-plane deformation and the C-N stretching vibration of 4-pyridinecarboxyaldehyde [ 34 , 43 ].…”

“…In the development of doped carbon dot sensors, guest molecules are introduced into the interior of the host carbon material. In this way, the host binds to the selective guest molecules introduced before other competing species and registers the binding event with a unique structural shape [ 15 , 16 , 34 ]. In this study, we use very simple and commercially available organic ligands (4-pyridinecarboxaldehyde and citric acid monohydrate) in the presence of Zn 2+ ions ( Scheme 1 ).…”

“…Ligand-based fluorescence emissions are usually attributed to particles containing d 10 metal ions that do not undergo d-d transitions. Therefore, the presence of zinc metal in the fluorescent carbon dots with mixed ligands can produce this type of ligand-based fluorescence emission [ 34 ]. Immobilized Lewis base pyridyl nitrogen sites located on the organic structure exhibit fluorescence properties and can selectively respond to metal ions [ 34 , 35 ].…”

“…Therefore, the presence of zinc metal in the fluorescent carbon dots with mixed ligands can produce this type of ligand-based fluorescence emission [ 34 ]. Immobilized Lewis base pyridyl nitrogen sites located on the organic structure exhibit fluorescence properties and can selectively respond to metal ions [ 34 , 35 ]. Techniques such as microwave irradiation [ 32 , 36 , 37 , 38 ] and hydrothermal treatment [ 33 ] have been reported in the literature for the synthesis of N,Zn CDs, and these CDs have mostly been used as biosensors or for detecting Fe(III).…”

Hydrogen-Bond-Connected 2D Zn-LMOF with Fluorescent Sensing for Inorganic Pollutants and Nitro Aromatic Explosives in the Aqueous Phase

“…Metal ions have played an important role in the development of human society for a long time. For example, Fe 3+ , an essential component of hemoglobin, undertakes the duty of oxygen transportation in human body and plays a momentous role in agriculture and industry. − As a potential carcinogen, Cr 6+ also plays an important role in industrial production processes such as ferrochromium smelting, metallurgy, and so forth. − As a result, untreated factory wastewater usually contains these two ions, which cannot be biodegraded and are likely to be enriched in the environment and eventually enter the human body through the food chain, , causing different kinds of diseases. − Therefore, monitoring of Fe 3+ and Cr 2 O 7 2– pollutants is necessarily required because of its enrichment in the environment.…”