Here, we report an improved tandem catalytic mechanism for electroreduction of CO2 to C2H4. Cu(111) nanoparticles with an average size of 5.5 ± 0.9 nm were anchored on a conductive Cu-based metal-organic framework (Cu-THQ) by in situ electrochemical synthesis. Compared to Cu(111) nanoparticles, the C2H4 faradaic efficiency of the tandem catalyst Cu(111)@Cu-THQ was increased doubly.