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 -oxo Fe+3-phenanthroline 1:1 complex [(OH2)3(Phen)FeOFe(Phen)(OH2)3]+4 (hereafter Fe+3Phen) 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+3Phen and Mt-Fe+3Phen. 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+3Phen 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 diffraction measurements show that in Mt the second layer formation is accompanied by a super- structuring of the interlayer that changes the thermal and chemical properties of the composite material. In particular, interesting catalytic properties are observed in Mt-Fe+3Phen samples, but they are completely suppressed with the formation of the Fe+3Phen bilayer structure.