The electronic character of porphyrin active sites for electrocatalytic reduction of CO2 to CO in a two-dimensional covalent organic framework (COF) was tuned by modification of the reticular structure.-Efficient charge transport along the COF backbone promotes electronic, connectivity between remote functional groups and the active sites, and-enables the modulation of the catalytic properties of the system. A series of oriented: thin :films of-these COFs was found to reduce CO2 to CO at low overpotential (550 mV) with high selectivity (fatadaic efficiency of 87%) and at high. current densities (65 mA/mg), a performance well beyond related molecular catalysts in regard to selectivity and efficiency. The catalysts are stable for more than 12 h without any loss in reactivity. X-ray absorption measurements on the cobalt L-edge for the modified COFs enable correlations between the inductive effects of the appended functionality and the electronic character of the reticulated molecular active sites.