Nanomaterials Based on Collaboration with Multiple Partners: Zn(3)Nb(2)O(8) Doped with Eu(3+) and/or Amino Substituted Porphyrin Incorporated in Silica Matrices for the Discoloration of Methyl Red

Designing appropriate materials destined for the removal of dyes from waste waters represents a great challenge for achieving a sustainable society. Three partnerships were set up to obtain novel adsorbents with tailored optoelectronic properties using silica matrices, Zn(3)Nb(2)O(8) oxide doped with Eu(3+), and a symmetrical amino-substituted porphyrin. The pseudo-binary oxide with the formula Zn(3)Nb(2)O(8) was obtained by the solid-state method. The doping of Zn(3)Nb(2)O(8) with Eu(3+) ions was intended in order to amplify the optical properties of the mixed oxide that are highly influenced by the coordination environment of Eu(3+) ions, as confirmed by density functional theory (DFT) calculations. The first proposed silica material, based solely on tetraethyl orthosilicate (TEOS) with high specific surface areas of 518–726 m(2)/g, offered better performance as an adsorbent than the second one, which also contained 3-aminopropyltrimethoxysilane (APTMOS). The contribution of amino-substituted porphyrin incorporated into silica matrices resides both in providing anchoring groups for the methyl red dye and in increasing the optical properties of the whole nanomaterial. Two different types of methyl red adsorption mechanisms can be reported: one based on surface absorbance and one based on the dye entering the pores of the adsorbents due to their open groove shape network.