Characterization of polyoxometalate/polymer photo‐composites: A toolbox for the photodegradation of organic pollutants

Key-to-lock halogen bond-based tetragonal pyramidal association of iodonium cations with the lacune rims of beta-octamolybdate

The structure-directing "key-to-lock" interaction of double σ-(IIII)-hole donating iodonium cations with the O-flanked pseudo-lacune rims of [β-Mo8O26]4- gives halogen-bonded iodonium-beta-octamolybate supramolecular associates. In the occurrence of their tetragonal pyramidal motifs, deep and broad σ-(IIII)-holes of a cation recognize the molybdate backbone, which provides an electronic pool localized around the two lacunae. The halogen-bonded I⋯O linkages in the structures were thoroughly studied computationally and classified as two-center, three-center bifurcated, and unconventional "orthogonal" I⋯O halogen bonds. In the latter, the O-atom approaches orthogonally the C-IIII-C plane of an iodonium cation and this geometry diverge from the IUPAC criteria for the identification of the halogen bond.

Green complexation for heavy metals removal from wastewater by Keggin-polyoxometalates enhanced ultrafiltration

The presence of heavy metals in wastewater has become a serious issue and a global concern for the environment and public health with rapid progress of modern textile industry. To minimize the health risks of heavy metals their complexation to a chelating agent constitute a promising process using membrane separation. We highlight for the first time the use of Keggin type-polyoxometalates (PW₁₂) as complexing agent to eliminate heavy metals from synthetic textile wastewater. Indeed, filtration experiments were performed through the ultrafiltration organic regenerated cellulose membrane (3KDa). Effects of pressure (1-2.5 bar), PW₁₂ concentration (10-50 mg·L^-1), salt concentration (10^-4-2 M) and pH value (2-12) on cadmium (Cd) and copper (Cu) removal were regularly explored. Experimental data showed that the addition of PW₁₂ improves metal removal efficiency (up to 90%). The addition of NaCl salt significantly decreases the metals retention to 42%. The retention drop is probably due to the competition between Na+ and metals on complexation same negative sites of the PW₁₂ and to the electric double-layer compressing. 2⁴ full factorial design has been used to evaluate the most influencing parameters. The results obtained revealed that the maximum metal retention was 99% for both Cd and Cu.