Photochemical Reduction of Carbon Dioxide to Methanol Using ZnS Microcrystallite as a Photocatalyst in the Presence of Methanol Dehydrogenase

Photoinduced reduction of formate to methanol has been achieved using microcrystalline colloid which contained formate, methanol dehydrogenase (MDH), pyrroloquinoline quinone (PQQ) as an electron mediator for MDH, and 2‐propanol. This reaction was combined with photoreduction of carbon dioxide to formate on the microcrystallite which had already been reported to provide a new photosynthetic route for production of methanol from carbon dioxide. The production of methanol showed a saturation tendency when it was accumulated to 0.25 mmol dm⁻³, probably due to oxidation of the produced methanol at MDH or on the photocatalyst or both. The concentration of PQQ influenced the amount of formate production but not the methanol production. The quantum efficiency obtained at 280 nm for the reduction of carbon dioxide to methanol was 5.9%, which is the highest value that has ever been reported for the photochemical reduction of carbon dioxide to methanol.