▎ 摘　　要

Herein, monolayer self-assembly of polyhedral oligomeric silsesquioxane (POSS) onto graphene oxide (GO) is facilely achieved by taking advantage of their electrostatic and hydrogen-bonding interaction. Attributed by the rigid nanocage and donor/acceptor effect of POSS, the as-prepared POSS-GO monolayer nanostructure (denoted as PG) shows an ultrathin thickness of 1.6 nm and significantly suppressed stacking. Followed by postfunctionalization of Cu2+, the POSS-GO-Cu2+ nanostructure (shortly termed as PGCu) exhibits outstanding performances including hemoglobin specificity, salt tolerance and ultrahigh adsorption capacity (up to 1657.2 mg g-1). Moreover, PGCu is successfully utilized for the separation of hemoglobin from human whole blood with the maintenance of protein activity. The present study furnishes a simple, rapid and cost-efficient route for the fabrication of ultrathin two-dimensional materials with considerable application potentialities for bio-separation and analysis.