A POSS derivative containing UV-curable methacrylate groups (methacryl-POSS) was used as a multi-functional cross-linker to form thin and durable hydrogel films with a hydrophilic comonomer, poly(ethylene glycol) methacrylate (PEGM), in the presence of photoinitiator. The water uptake of the crosslinked POSS-PEGM films was easily controlled from 8% to 90% by manipulating the weight ratio of methacryl-POSS and PEGM from 1:1 to 1:20. Further improvement in the water uptake was demonstrated by adding a sacrificial additive into the prepolymerization mixture of methacryl-POSS and PEGM. The addition of water soluble, non-crosslinkable polyethylene glycol (PEG) into a prepolymerization mixture and subsequent extraction of the PEG additive after UV-curing creates molecular-scale pores within the crosslinked film, resulting in significant increase in water uptake as well as water permeability of the film. The free standing film prepared from the prepolymerization mixture containing 1:20 weight ratio of methacryl-POSS and PEGM with 50wt% PEG additive showed the highest water uptake (280%) and water permeability (130Lμmm -2h -1atm -1) among tested samples. PSF UF membranes coated with the highly water permeable, nanoporous POSS-PEGM materials showed excellent anti-fouling efficiency when tested in a cross-flow filtration system using an oil-water emulsion or a bovine serum albumin (BSA) solution as the feed. Molecular dye filtration studies conducted with a relatively dense POSS-PEGM material (MWCO<1kDa) showed the potential of this material as a nanofiltration membrane as well. © 2012 Elsevier B.V.