To improve the electrocatalytic conversion of carbon dioxide (CO2) into C2+ products (such as ethylene (C2H4) and ethanol (CH3CH2OH), etc.) is of great importance, but remains challenging. Herein, we proposed a strategy that directs the C–C coupling pathway through enriching and confining the carbon monoxide (CO) intermediate to internal pores of Cu nanocubes, for electrocatalytic reduction of CO2 into C2+ chemicals. In H-type cell, the Faraday efficiency (FE) for ethylene and ethanol reaches 70.3% at −1.28 V versus the reversible hydrogen electrode (vs. RHE), with a current density of 47.9 mA·cm−2. In flow cell, the total current density is up to 340.3 mA·cm−2 at −2.38 V (vs. RHE) and the FE for C2+ products is 67.4%. Experimental and theoretical studies reveal that both the CO intermediate adsorption and C–C coupling reaction on such an internal porous catalyst are facilitated, thus improving CO2-to-C2+ conversion efficiency.