Nanoporous membranes with antifouling properties and narrow pore size distribution targeted at a nanometer and subnanometer separation capacity hold great promise in high end value molecular sieving and bioseparation. Herein a novel strategy is presented for preparation of well-defined nanoporous membranes with tunable nanopores via click chemistry. The graft polymerization based on copper(I)catalyzed azide-alkyne cycloaddition (CuAAC) was successfully conducted at ambient conditions to tether monodispersed propargyl poly(ethylene glycol)s (pro-PEGs) onto a microporous polysulfone (PSF) membrane anchored with azide groups. The solute transport method indicates that a series of nanoporous membranes with narrowed pore size distribution and the mean pore diameter of 1.20 nm, 0.82 nm and 0.69 nm were obtained. The protein filtration experiments show that membrane surface can be endowed with antifouling properties by the densely grafted PEG. The membrane effectively rejects emulsified oil at 0.5 MPa with less fouling than the thin film composite membrane. The molecular sieving capacity is demonstrated through separation of dyes varying in several angstroms. (C) 2012 Elsevier B.V. All rights reserved.