Sulfur-Bridged Co(II)-Thiacalix[4]arene Metal-Organic Framework as an Electrochemical Sensor for the Determination of Toxic Heavy Metals.

A novel sulfur-bridged metal-organic framework (MOF) [Co(TIC4R-I)0.25Cl2]·3CH3OH (Co-TIC4R-I) based on thiacalix[4]arene derivatives was successfully obtained using a solvothermal method. Remarkably, adjacent TIC4R-I ligands were linked via Co(II) cations to form a three-dimensional (3D) microporous architecture. Subsequently, Co-TIC4R-I was modified on a glassy carbon electrode (Co-TIC4R-I/GCE) to produce an electrochemical sensor for the detection of heavy-metal ions (HMIs), namely, Cd2+, Pb2+, Cu2+, and Hg2+, in aqueous solutions. It was found that Co-TIC4R-I/GCE exhibited wide linear detection ranges of 0.10-17.00, 0.05-16.00, 0.05-10.00, and 0.80-15.00 µM for Cd2+, Pb2+, Cu2+, and Hg2+, respectively, in addition to low limit of detection (LOD) values of 0.017, 0.008, 0.016, and 0.007 µM. Moreover, the fabricated sensor employed for the simultaneous detection of these metals has achieved LOD values of 0.0067, 0.0027, 0.0064, and 0.0037 µM for Cd2+, Pb2+, Cu2+, and Hg2+, respectively. The sensor also exhibited satisfactory selectivity, reproducibility, and stability. Furthermore, the relative standard deviation (RSD) values of Cd2+, Pb2+, Cu2+, and Hg2+ were 3.29, 3.73, 3.11, and 1.97%, respectively. Moreover, the fabricated sensor could sensitively detect HMIs in various environmental samples. The high performance of the sensor was attributed to its sulfur adsorption sites and abundant phenyl rings. Overall, the sensor described herein provides an efficient method for the determination of extremely low concentrations of HMIs in aqueous samples.

CdII-based compound as a multi-responsive fluorescent probe for sensing FeIII cations and CrVI oxyanions.

A new luminescent CdII compound, poly[[µ2-1,4-bis(1H-imidazol-1-yl)benzene]{µ2-5-[(3-carboxylphenoxy)methyl]isophthalato}cadmium(II)], [Cd(C16H10O7)(C12H10N4)]n or [Cd(HL)(1,4-bib)]n {H3L is 5-[(3-carboxyphenoxy)methyl]isophthalic acid and 1,4-bib is 1,4-bis(1H-imidazol-1-yl)benzene}, I, has been synthesized successfully from CdII and a semirigid tricarboxylic ligand under hydrothermal conditions. Structure analysis shows that I is a two-dimensional structure with the point symbol {44.62}. The three-dimensional framework is constructed by O-H...O hydrogen bonds and π-π stacking interactions. Furthermore, the obtained CdII compound displays high solvent stability and excellent thermal stability, as shown by powder X-ray diffraction and thermogravimetry measurements. Studies of the luminescence properties reveal that compound I can act as a promising luminescent sensor for detecting FeIII cations and CrVI oxyanions with high selectivity and low detection limits (0.19 µM for Fe3+ and 1.13 µM for Cr2O72-), and is additionally free from the interference of other ions. The mechanism of selective quenching was studied by measuring the UV-Vis absorption of the host compound and the target analytes.