Turbostratic nanoporous carbon sheet membrane for ultrafast and selective nanofiltration in viscous green solvents

Development of ultrafast and selective nanofiltration membranes for viscous green solvents, such as isopropyl alcohol (IPA), is a big challenge in the chemical, food, and pharmaceutical industries. However, all existing nanofiltration membranes, including polymers, have been critically limited by low solvent permeance and low selectivity for solute molecules with a nanoscale feature dimension. This might be attributed to narrow channel structures and strong interaction between membrane materials and viscous green solvents. Herein, we significantly enhanced the nanofiltration performance in IPA by using a turbostratic nanoporous carbon sheet membrane, which was prepared by rapid thermal treatment of graphene oxide. Sharp separation of viscous alcohol and molecules smaller than 600 Da from larger molecules (molecular weight cut-off: 600 Da) was achieved by using the developed membrane with an ultrafast IPA permeance of ~1800 L m^-2h^-1bar^-1(LMH bar^-1). The membrane performance far exceeds the upper bound of existing nanofiltration membranes, as reflected by the IPA permeance being two orders of magnitude greater than those for commercially available membranes, sustaining high rejection rates for sub-nanometer size molecules.