On the nature of Cr species on MCM-41 obtained by a one step method and their enhanced photocatalytic performance under visible radiation: New insights by a combined techniques approach

• Direct incorporation of Cr in synthesis gel allows synthesized highly ordered MCM-41.
• Presence of highly dispersed Cr6+ species was verified by spectroscopic techniques.
• After Ti load, the Cr6+ dispersion allows a strong heterojunction effect.
• The higher dispersion and accessibility of active Cr species allow synthesized efficient photocatalysts.
• An efficient use of visible radiation was reached, allowing high AO7 degradation.

MCM-41 materials modified with several Cr/Si molar ratios by a direct incorporation method and then with Ti by impregnation, were characterized by different instrumental techniques. In order to develop new photocatalysts that uses more efficiently solar light, the aim of this work was to evaluate the direct incorporation method to synthesize Cr-modified MCM-41. The synthesized solids were tested as photocatalysts for the Acid Orange 7 (AO7) degradation in aqueous solution. The catalysts with Si/Cr molar ratios of 60 and 40 led to AO7 degradations higher than 70% after the Ti loading. Thus, it could be confirmed that the direct incorporation method of Cr in the synthesis gel favored the high dispersion of the active species of Cr6+ making them accessible to interact with Ti species. Finally, the presence of Ti is crucial to achieve a better use of the radiation due to the synergistic effect with the Cr species besides avoiding the loss of this metal to the reaction medium.

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