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 Fe+3Phen complex strongly adsorbs both on kaolinite and montmorillonite.
• The adsorption of the complex is described by an isotherm of VI type.
• Intercalation in montmorillonite leads to superstructuring of the interlayer.
• The superstructured interlayer imparts montmorillonite with appealing properties.

The μ-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 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.

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