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A thorough analysis about iron speciation in the direct Fe-SBA-15 synthesis by using metal precursors with distinct counter-ions: (NO3)−, (SO4)2−, Cl− and (C5H7O2)− is presented. Long-range hexagonal ordering and high specific areas were achieved for all of silicates. Although a Si/Fe molar ratio of 20 allowed incorporating a similar metal content in the materials, several iron species were formed as a function of metal source. The solids were tested as Fenton catalysts for the paracetamol degradation and the importance of the different developed metal species on the catalytic efficiency could be corroborated. The presence of sulfate groups in the synthesis gel led to more active catalysts. Here, isolated Fe3+ ions, stabilized on the structure by multiple oxygen bridge bonds, could interact more efficiently with H2O2 to generate OH· oxidative species for the degradation of organic molecules. Finally, it was demonstrated that by means of sol–gel method and pH conditions control, it is possible handling the metal precursor to achieve certain chemical species on the surface with a higher catalytic efficiency for Fenton process. [ABSTRACT FROM AUTHOR]