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Abstract Two-dimensional (2D) materials, as adsorbents, have garnered great attention in removing heavy metal ions (HMIs) from drinking water due to their extensive exposed adsorption sites. Nevertheless, there remains a paucity of experimental research to remarkably unlock their adsorption capabilities and fully elucidate their adsorption mechanisms. In this work, exceptional lead ion (Pb2+) (a common HMI) removal capacity (up to 758 mg g−1) is achieved using our synthesized metallic 1T/1T′ phase 2D transition metal dichalcogenide (TMD, including MoS2, WS2, TaS2, and TiS2) nanosheets, which hold tremendous activated S chemisorption sites. The residual Pb2+ concentration can be reduced from 2 mg L−1 to 2 μg L−1 within 0.5 min, meeting the drinking water standards following World Health Organization guideline (Pb2+ concentrations <10 μg L−1). Atomic-scale characterizations and calculations based on density functional theory unveil that Pb2+ bond to the top positions of transition metal atoms in a single-atom form through the formation of S-Pb bonds. Point-of-use (POU) devices fabricated by our reported metallic phase MoS2 nanosheets exhibit treatment capacity of 55 L-water g−1-adsorbent for feed Pb2+ concentration of 1 mg L−1, which is 1-3 orders of magnitude higher than other 2D materials and commercial activated carbon.