The synthesis of a single‐layer covalent organic framework (COF) with spatially modulated internal potentials provides new opportunities for manipulating the electronic structure of molecularly defined materials. Here, the fabrication and electronic characterization of COF‐420: a single‐layer porphyrin‐based square‐lattice COF containing a periodic array of oriented, type II electronic heterojunctions is reported. In contrast to previous donor–acceptor COFs, COF‐420 is constructed from building blocks that yield identical cores upon reticulation, but that are bridged by electrically asymmetric linkers supporting oriented electronic dipoles. Scanning tunneling spectroscopy reveals staggered gap (type II) band alignment between adjacent molecular cores in COF‐420, in agreement with first‐principles calculations. Hirshfeld charge analysis indicates that dipole fields from oriented imine linkages within COF‐420 are the main cause of the staggered electronic structure in this square grid of atomically–precise heterojunctions. A single‐layer covalent organic framework (COF) that exhibits a staggered internal potential between neighboring bright and dark molecular cores is shown. Donor/acceptor functionality between the structurally identical cores arises from electronic dipoles incorporated into the linkers between them. The resulting two COF sublattices are observed to be offset in energy by 0.25 eV, consistent with first‐principles calculations.