This proposal addresses topic 12(a) High Selectivity Membranes aimed at the advancement of manufacturing processes to produce atomically thin membranes with exceptional selectivity that are required to improve the energy efficiency and costs of a multitude of separation processes. Single-layer nanoporous graphene membrane where sub-nanometer pores permit selective transport with little resistance is potentially the most disruptive next-generation membrane for major membrane separation processes including desalination of water by reverse osmosis (RO), gas separations, and organic solvent nanofiltration. Graphene membranes have the potential for improvement in energy efficiency of separation, high chemical stability with substantially longer membrane life, compact plants with lower operational costs, improved selectivity, and minimal concerns regarding toxicity. However, a scalable and cost-effective process to produce precisely sized pores in large-area graphene is needed before this technology can be developed for commercialization. This Phase I SBIR proposal will address this key challenge through development of a process for rapidly creating tunable, nanometer-scale pores in graphene, followed by a simple approach to selectively block pores above a certain diameter, leading to large-area membranes with a precise pore size cutoff. Phase II will advance this technology by developing scalable manufacturing methods to enable roll-to-roll production and packaging of the membrane into functional modules. Successful completion of this project will address a critical challenge in the field and bring this potentially transformative membrane significantly closer to commercialization for applications in organic solvent processing, oil and natural gas, as well as water purification and desalination. The project aims to tackle key challenges to realize scalable and cost-effective manufacture of atomically thin graphene membranes for energy- efficient separations for water, oil and natural gas, and organic solvent separations.