Traditionally, Fe-SACs are prepared through energy-intense processes, which often lead to the loss of precision in structural features from the starting substrates and impeding rational design. We herein described the synthesis of a unique catechol-containing porous polymer with designed features in the substrates maintained, affording atomically dispersed iron catalyst (Fe-SAC) through treatment of ferrous chloride (FeCl2). An aberration-corrected scanning transmission electron microscope (AC-STEM) and synchrotron X-ray absorption spectroscopy (XAS) were employed to shed light on the local coordination geometry of the atomically dispersed iron catalyst. The resulting Fe-SAC exhibits excellent catalytic performance in reduction of nitroaromatics with highest molar K-app among all Fe based catalysts.