A method for reducing carbon dioxide with use of a device for reducing carbon dioxide includes steps of (a) preparing the device. The device includes a vessel, a cathode electrode and an anode electrode. An electrolytic solution is stored in the vessel, the cathode electrode contains a copper rubeanate metal organic framework, the copper rubeanate metal organic framework is in contact with the electrolytic solution, the anode electrode is in contact with the electrolytic solution, and the electrolytic solution contains carbon dioxide. The method further includes step of (b) applying a voltage difference between the cathode electrode and the anode electrode so as to reduce the carbon dioxide.