Stepwise structuring of the adsorbed layer modulates the physico-chemical properties of hybrid materials from phyllosilicates interacting with the μ-oxo Fe+3-phenanthroline complex

The mu-oxo Fe+3-phenanthroline 1:1 complex [(OH2)(3)(Phen)FeOFe(Phen)(OH2)(3)](+4) (hereafter Fe(+3)Phen) was successfully immobilized on montmorillonite (Mt) and kaolinite (Kt) minerals. Adsorption data on both minerals described an adsorption isotherm of VI type and were successfully fitted using two independent Frumkin isotherms. The interaction between the complex and the minerals is strong and yields two stable hybrid materials: Kt-Fe(+3)Phen and Mt-Fe(+3)Phen. DR UV-Vis, elemental analysis, TGA-MSEGA, temperature-controlled XRPD techniques were used to characterize the structural properties of the hybrid materials. These investigations showed that the Fe(+3)Phen adsorption occurs stepwise via the formation of a bilayer structure. The first layer is the result of a cation exchange process involving the negative charges of the mineral, while the second one probably forms through stacking interaction and/or sulphate ions bridging. XRD measurements show that for Mt the interaction between the mineral and the complex occurs especially in the interlayer and the second layer formation is accompanied by a super-structuring of the interlayer that changes the thermal stability and physico-chemical properties of the composite material. (C) 2015 Elsevier Inc. All rights reserved.