Because　of　the　high　efficiency　and　mild　reaction　conditions,　electrocatalytic　CO2　reduction　(ECR)　has　attracted　significant　attention　in　recent　years.　However,　the　specific　mechanism　of　the　formation　of　the　two-electron　production　(CO　or　HCOOH)　in　this　reaction　is　still　unclear.　Herein,　with　density　functional　theory　calculation　and　experimental　manipulation,　the　specific　mechanism　of　the　selective　two-electron　reduction　of　CO2　has　been　systematically　investigated,　employing　the　polyphenolate-substituted　metalloporphyrinic　frameworks,　ZrPP-1-M　(M　=　Fe,　Co,　Ni,　Cu,　and　Zn),　as　model　catalysts.　Experimental　observations　and　theoretical　calculations　discovered　that　ZrPP-1Co　is　a　more　favorable　catalyst　for　ECR　among　them.　Compared　with　the　formation　of　HCOOH,　electroreduction　of　CO2　into　CO　has　more　beneficial　thermodynamic　and　kinetic　routes　with　ZrPP-1-Co　as　a　catalyst.　After　introducing　the　r-GO　for　improving　the　conductivity,　the　Faradaic　efficiency　for　CO　formation　is　82.4%　at　-0.6　v　(vs　RHE).