Uranium extraction from seawater has attracted increasing attentions for nuclear raw material to support the sustainable development of nuclear power plants. However, it is still a grand challenge to overcome the high salinity background and ultra-low uranyl concentration. Herein, we successfully achieved Fe-Nx configurations embedded in graphitic carbon nitride (FeNx/g-C3N4) through one-step pyrolysis strategy. Our density function theory (DFT) calculations reveal that the site-isolated FeNx centers are the predominant binding sites for U(VI) species, and visible-light photoexcitation can effectively facilitate the electron escaping from FeNx/g-C3N4 surface relative to pure g-C3N4, which is consequently favorable for electron transfer in the photoreduction conversion of U(VI) to U(IV). Consistent with the theoretical results, the obtained FeNx/g-C3N4 (w(Fe-MOFs): w(g-C3N4) = 2:1) delivers remarkably higher reduction activity with the conversion efficiency of 99 % and rate constant of 0.091 min−1, almost 9.1 and 12.5 times faster than those of g-C3N4 and TiO2 catalysts, respectively. The results showed that the introduction of FeNx could effectively activate g-C3N4 catalysts for significantly broadening the absorption range of g-C3N4 to visible light, inhibiting recombination of the photogenerated e--h+ and further facilitating the reduction of U(VI). It is worthwhile to mention that FeNx/g-C3N4 maintains a high level for the extraction of uranium from seawater, endowing the metal-N configurations embedded g-C3N4 as a kind of promising candidate for the sustainable conversion of radionuclides.