Porous single crystals have the characteristics of long-range ordering structure and large specific surface area, which will significantly enhance their electrochemical performance. Here, we report a method different from the conventional porous single crystal growth method. This method is to directly convert single crystal precursors Co₃O₄ and Fe₃O₄ into Co₂N and Fe₂N, and then further reduces them to porous single crystals Co and Fe particles under H₂/Ar atmosphere. The removal of O^2– in the lattice channel at the pressure of 25～300 torr and the temperature of 300～600 °C will promote nitridation of the single-crystalline Co–O and Fe–O frames, and further remove N^3– in H₂/Ar atmosphere and recrystallize as Co and Fe. These porous single crystals exhibit enhanced electrochemical properties due to their structural coherence and highly active surface. We demonstrated that the aminobenzene yield was up to 91% and the selectivity reached 92% in the electrochemical reduction of nitrobenzene.