In this study, Fermi levels of graphitic carbon nitride (CN), black phosphorus (BP), and graphene quantum dots (GQDs) were rationally combined and tuned through a band engineering approach. The structure−activity relationship of the resulting heterojunction was characterized by using a combination of X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and solid-state nuclear magnetic resonance techniques. The results revealed that CN and BP were in contact through the formed P−N bridges, while the polar functional groups of GQDs interacted with BP and CN via P−O and N−O interactions, respectively. The superior degradation efficiency is attributed to the synergistic effect of the strong coupling at the interfaces where GQDs@CNBP was tested in removal of organic pollutants [methyl orange (MO) and tetracycline (TC)]. The degradation intermediates in both cases were enlightened by NMR experiments showing no trace of either pollutant or photocatalyst in wastewater. The photogenerated charge migration mechanism was experimentally elucidated as a complex-type-II, which is based on the usage of the farthest charges on the band edges. Scavenger experiments and photooxidation of glucose confirmed the in situ generation of oxidative species of • O 2 − , H 2 O 2 , and • OH, which played a vital role in the photooxidation reactions. A GQDs@CNBP heterojunction with the kinetic rate constants of 0.1415 min −1 (30 min) for MO and 0.0371 min −1 (120 min) for TC is one of the highest kinetics that has been reported in the literature so far.