Catalytic aqueous CO2 reduction to formaldehyde at Ru surface on hydroxyl-groups-rich LDH under mild conditions

Various value-added chemicals such as formic acid , carbon monoxide , methane, methanol, have been obtained using CO 2 as a feedstock. However, formaldehyde generation from CO 2 is less reported. Here, we performed CO 2 hydrogenation with H 2 in additive-free water and used layered double hydroxide supported Ru as the heterogeneous catalyst. It was found that gaseous CO 2 and H 2 could be efficiently and selectively converted to formaldehyde dissolved in water even at room temperature with ambient pressure. The highest gaseous CO 2 conversion of 89.7% and a formaldehyde yield of 58.7% were achieved using a Ru/LDH-red catalyst in water at 30 °C with 10 bar CO 2 and 10 bar H 2 . Combined with experimental and theoretical studies, HCOOH was found as the important reaction intermediate. The rich surface –OH of LDH and hybrid electronic state of Ru over Ru/LDH-red catalyst resulted in highly efficient HCHO formation. Our findings offer opportunities to one energy-efficient formaldehyde synthesis method.