The increase of carbon dioxide(CO2)in the atmosphere has become a global environmental issue with the threat of global warming.[1] Graphene-like carbon nitride(g-C3N4)as a metal-free 2D material show great potential application in the field of CO2 reduction into fuels and chemicals.[2,3] However,the most of prepared g-C3N4 are not ideal candidate catalysts due to their low catalytic rate for CO2 reduction.In this work,density functional theory(DFT)calculations are performed to explore the role of Cu or Mo loading on g-C3N4(001)for reducing the energy barriers of CO2 reduction to CO.