This work demonstrates a novel nanomaterial for rapid, efficient and selective enrichment as well as portable separation of Hg(II) ions, which integrates the advantages of hydrophilic porous cellulose fibers and specific Hg(II) recognizing CuS nanoparticles. The optimal CuS/cellulose fibers nanomaterial (CC-60) exhibits a markedly faster adsorption rate, reaching adsorption equilibrium within 30 s, and a large Hg(II) uptake capacity as high as 1040 mg g^-1 in 2 min. The distribution coefficient (K_d) of CC-60 for Hg(II) ions is four orders of magnitude higher than those for other common metal ions, thus giving unique selectivity for Hg(II) ions in the presence of other common metal ions. CC-60 can be used in portable column devices for the sequestration of Hg(II) ions from practical water samples, rapidly lowering the Hg(II) concentration from 16.6 mg L^-1 to 9 μg L^-1 in 5 s, which surpasses all those sulfur-based materials reported thus far. Such exciting properties are closely related to the synergistic effects arising from the porous structure and hydrophilicity of cellulose fibers, the unique recognition capability of CuS towards Hg(II), and the readily accessible CuS sites on cellulose fibers. This work would open up a new avenue to materials and devices for fast recognition, sequestration, enrichment and detection of Hg(II) as well as other toxic heavy metal ions.