Performance and mechanism of CuO/CuZnAl hydrotalcites-ZnO for photocatalytic selective oxidation of gaseous methanol to methyl formate at ambient temperature

• CuO/CuZnAl LDH-ZnO exhibits good photoactivity for oxidation of methanol to methyl formate.
• CuO is photoreduced to Cu during the reaction under UV irradation.
• The maximum methyl formate yield reaches 50% at 30 °C.
• The study provides new insights into the design of photocatalysts for methanol oxidation.

The photocatalytic selective oxidation of methanol to methyl formate at 26–45 °C under UV irradiation has been studied for the first time on the catalyst CuO supported on nanocomposites of CuZnAl hydrotalcites and ZnO. The catalyst exhibits high activity for this reaction, with a maximum methyl formate yield of 50% at 30 °C and no by-product other than CO2, although both ZnO and hydrotalcites are nonactive for the reaction. The interfaces between ZnO and CuZnAl hydrotalcites play an important role in the reaction, not only supplying necessary hydroxyls but also generating holes with redox potential positive enough for the reaction under UV irradiation due to the band bending at the interface. Copper oxide is photoreduced to metallic Cu during the reaction, which plays a role in trapping photoexcited electrons from the conduction band of the support as well as in dissociating chemisorbed oxygen.

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