Fenton or photocatalytic degradations of organic contaminants are recognized as promising approaches to address the increasing environmental pollution issues. Herein, we develop the effective synergistic catalysis reaction of Fenton and photocatalysis based on a loofah sponge-like Fe₂O_x/C nanocomposite, which exhibits excellent nitrobenzene photocatalytic degradation property. It is noted that Fe₂O₃ nanoparticles with surface Fe²⁺ species were encapsulated with an ultrathin carbon layer (denoted as Fe₂O_x/C) via a supramolecular self-sacrificing template and following thermal treatment process. The experimental results indicated that the thin layer carbon coating not only inhibited the Fe iron leaching from the Fe₂O_x but also prompted the separation and transferring of electrons–hole pairs. The introduction of Fe₂O_x/C enables the Fenton reaction to induce a rapid Fe²⁺/Fe³⁺ cycle, and meanwhile, together with the photocatalytic reaction to produce continuous active substances for the subsequent degradation catalytic reaction without successive H₂O₂, resulting in the inexpensive and the effective photocatalytic procedure. As a result, 100% nitrobenzene (100 mg/L) was degraded and 97% of the organic carbon was mineralized in 90 min using the Fe₂O_x/C (0.1 g/L) at a low H₂O₂ dosage (0.50 mM), under air mass (AM) 1.5 irradiation. Theoretical calculations confirmed that the Fe₂O_x/C-600 with thin carbon layer promoted the dissociation of H₂O₂ and the ·OH desorption. The synergistic catalysis of this work may provide new ideas for low-cost and more efficient treatment of pollutants.