Large-scale disposal of mercury derivatives via industries into the ecosystem created ever-lasting pollution in nature that could lead to bioaccumulation and put living species' lives in danger; hence, it is vital to remove these hazardous pollutants using practical approaches. Herein, this requirement is addressed by developing a 2D absorber with active sulfur domains composed of polythiophene (PT), AgxIx, and sodium diethyldithiocarbamate (PT-AgI-D). The developed configuration exhibited record-high absorption capacity and Femto molar-level sensitivity toward absorption and detection of mercury derivatives, viz., Hg metallic (Hg (m)), HgCl2, and HgO. Accordingly, the PT-AgI-D showed a superior removal capacity of 733.7, 186.6, and 299.4 mg g−1 toward the absorption of Hg (m), HgCl2, and HgO from aquatic media, respectively, with a yield of 99% at optimum conditions. More importantly, the absorber exhibited a detection limit (DL)/sensitivity of 11.86/79.57, 20.04/44.62, and 32.83/35.11 fM/(µA/fM) cm−2 toward Hg (m), HgCl2, and HgO, respectively. Furthermore, precise assessments revealed favorable reproducibility, selectivity, stability, and reusability of the absorber even after 20 adsorption–desorption cycles, highlighting its superior performance in removing mercury derivatives from aquatic media.